Showing posts with label Seminar Topics. Show all posts
Showing posts with label Seminar Topics. Show all posts
Thursday, August 27, 2009
Brain Computer Interface
A Brain Computer Interface is a device that enables people to interact with computer based systems through conscious control of their thoughts. BCI is any system that can derive meaningful information directly from the user’s brain activity in real time. The current and most important application of BCI is the restoration of communication channel for patients with locked-in-syndrome. Most current BCI’s are not invasive. The electrodes pick up the brain’s electrical activity and carry it into amplifiers. These amplifiers amplify the signal approximately ten thousand times and then pass the signal via an analog to digital converter to a computer for processing. The computer processes the EEG signal and uses it in order to accomplish tasks such as communication and environmental control.
BioChip
The development of biochips is a major thrust of the rapidly growing biotechnology industry, which encompasses a very diverse range of research efforts including genomics, proteomics, and pharmaceuticals, among other activities. Advances in these areas are giving scientists new methods for unraveling the complex biochemical processes occurring inside cells, with the larger goal of understanding and treating human diseases. At the same time, the semiconductor industry has been steadily perfecting the science of microminiaturization.The merging of these two fields in recent years has enabled biotechnologists to begin packing their traditionally bulky sensing tools into smaller and smaller spaces, onto so-called biochips. These chips are essentially miniaturized laboratories that can perform hundreds or thousands of simultaneous biochemical reactions. Biochips enable researchers to quickly screen large numbers of biological analytes for a variety of purposes, from disease diagnosis to detection of bioterrorism agents.
A biochip is a collection of miniaturized test sites (microarrays) arranged on a solid substrate that permits many tests to be performed at the same time in order to achieve higher output and speed. Biochips can also be used to perform techniques such as electrophoresis or PCR using microfluidics technology (Fan, 2009; Cady, 2009).
== History ==oxygen electrode, thereby relating oxygen levels to glucose concentration. This and similar biosensors became known as enzyme electrodes, and are still in use today.
In 1953, Watson and Crick announced their discovery of the now familiar double helix structure of DNA molecules and set the stage for genetics research that continues to the present day (Nelson, 2000).
The development of sequencing techniques in 1977 by Gilbert (Maxam, 1977) and Sanger (Sanger, 1977) (working separately) enabled researchers to directly read the genetic codes that provide instructions for protein synthesis. This research showed how hybridization of complementary single oligonucleotide strands could be used as a basis for DNA sensing. Two additional developments enabled the technology used in modern DNA-based biosensors. First, in 1983 Kary Mullis invented the polymerase chain reaction (PCR) technique (Nelson, 2000), a method for amplifying DNA concentrations. This discovery made possible the detection of extremely small quantities of DNA in samples. Second, in 1986 Hood and coworkers devised a method to label DNA molecules with fluorescent tags instead of radiolabels (Smith, 1986), thus enabling hybridization experiments to be observed optically.
BIOGAS in INTERNAL COMBUSTION ENGINE
1. S. I. Engines
The only adoption for a spark ignition engine is a gas (not gasoline!) carburetor to work at the supply pressure (just like an LPG conversion, but an evaporator would not be needed as the storage pressure is low). It is also a good idea to scrub the H2S (as it causes corrosion) and to derate the engine (unless you want to replace it each year if operating continuously).
Modification of S.I. Engine
S.I. engines can run completely on biogas, however, the engines are required to be started on petrol at the beginning, conversion of S.I. engine for the entry of biogas, throttling of intake air & advancing the ignition timing. Biogas can be admitted to S.I. engine through the intake manifold & air flow control valve can be provided on the air cleaner pipe connecting air cleaner & carburetor for throttling the intake air.
2. C.I.Engine:- .
iesel engines also need a gas carburetor and scrubbing, but require at least 10% diesel via the injectors for ignition (and cooling). The initial starting of diesel engine is done on pure diesel
Modification of C.I. Engine:–
C.I. engine can operate on dual fuel & the necessary engine modification include provision for the entry of biogas with intake air, provision of carburetor & system to reduce diesel supply, advanced injection timing. The entry of biogas and mixing of gas with intake air can be achieved by providing the mixing chamber below the air cleaner which facilitate through mixing of biogas with air before entering into the cylinder.
The arrangement is shown in fig. is largely used in stationary engine commercially available in India. The capacity of mixing chamber may be kept equal to the engine displacement volume. The pilot injection of cycle is required to be advanced for smooth and efficient running of engine on dual fuel. The admittance of biogas into the engine at the initial stage increases engine speed and therefore a suitable system reduces the diesel supply by actuating the control rack needs to be incorporated.There is a wide range of thoughts on what treatments should these biogases be subjected to before being used as fuel. Most operators simply remove the water present in the biogas, leaving it to the engine manufacturers to design engines which will cope with the impurities inevitably included in the biogas (significant maintenance costs);
other Operators are seriously evaluating maintenance costs against initial investments in biogas clean up technologies such as has been developed by Acrion Technologies (although Acrion's technologies are mainly aimed at biogas contaminant removal and separation into methane and carbon dioxide as feed stocks for a variety of commercial applications).
PRACTICAL DIFFICULTIES
To use the biogas as a fuel in SI engine there are some practical difficulties. It is not possible to compress the methane, separated from biogas by available method, because the gas could be liquefied through chilling below -161 0C. This process is adapted by installing the units required when there use of methane separated from biogas as a fuel. Since gas can not be compressed it requires large space for storage.
PERFORMANCE
1. In purification method, by reducing CO2 and moisture along H2S impurities in biogas, the engine performance is improved.
2. Effect of spark timing :-Biogas is slow burning fuel. Hence in order to get optimum engine performance, spark timing does not advance, and then combustion continues in major part of the expansion stroke. This reduces effective work done. By advancing, spark timing power is improved on low speed at partial throttle condition as well as high speed at full throttle condition.
EXHAUST EMMISSIONS
The exhaust emission contains three specific substances which contribute the air pollution, hydrocarbon, carbon monoxide &oxides of nitrogen. Hydrocarbons are the unburned fuel vapour coming out with the exhaust due to incomplete combustion. Hydrocarbon also occurring in crankcase by fuel evaporation. The emission of hydrocarbon is closely related to many design &operating factors like induction system, combustion chamber design, air fuel ratio, speed, load. Lean mixture lower hydrocarbon emission.Carbon monoxide occurs only in engine exhaust.
It is the product of incomplete combustion due to insufficient amount of air in air- fuel mixture. Some amount of CO is always present in the exhaust even at lean mixture. When the throttle is closed to reduce air supply at the time of starting the vehicle, maximum amount of CO is produced. Oxides of nitrogen are the combination of nitric oxide & nitrogen oxide &availability of oxygen are the two main reasons for the formation of oxides of nitrogen. The spark advance means lower peak combustion temperature. It causes high NO concentration in the exhaust. With biogas, co emission levels are low than that of gasoline.
The only adoption for a spark ignition engine is a gas (not gasoline!) carburetor to work at the supply pressure (just like an LPG conversion, but an evaporator would not be needed as the storage pressure is low). It is also a good idea to scrub the H2S (as it causes corrosion) and to derate the engine (unless you want to replace it each year if operating continuously).
Modification of S.I. Engine
S.I. engines can run completely on biogas, however, the engines are required to be started on petrol at the beginning, conversion of S.I. engine for the entry of biogas, throttling of intake air & advancing the ignition timing. Biogas can be admitted to S.I. engine through the intake manifold & air flow control valve can be provided on the air cleaner pipe connecting air cleaner & carburetor for throttling the intake air.
2. C.I.Engine:- .
iesel engines also need a gas carburetor and scrubbing, but require at least 10% diesel via the injectors for ignition (and cooling). The initial starting of diesel engine is done on pure diesel
Modification of C.I. Engine:–
C.I. engine can operate on dual fuel & the necessary engine modification include provision for the entry of biogas with intake air, provision of carburetor & system to reduce diesel supply, advanced injection timing. The entry of biogas and mixing of gas with intake air can be achieved by providing the mixing chamber below the air cleaner which facilitate through mixing of biogas with air before entering into the cylinder.
The arrangement is shown in fig. is largely used in stationary engine commercially available in India. The capacity of mixing chamber may be kept equal to the engine displacement volume. The pilot injection of cycle is required to be advanced for smooth and efficient running of engine on dual fuel. The admittance of biogas into the engine at the initial stage increases engine speed and therefore a suitable system reduces the diesel supply by actuating the control rack needs to be incorporated.There is a wide range of thoughts on what treatments should these biogases be subjected to before being used as fuel. Most operators simply remove the water present in the biogas, leaving it to the engine manufacturers to design engines which will cope with the impurities inevitably included in the biogas (significant maintenance costs);
other Operators are seriously evaluating maintenance costs against initial investments in biogas clean up technologies such as has been developed by Acrion Technologies (although Acrion's technologies are mainly aimed at biogas contaminant removal and separation into methane and carbon dioxide as feed stocks for a variety of commercial applications).
PRACTICAL DIFFICULTIES
To use the biogas as a fuel in SI engine there are some practical difficulties. It is not possible to compress the methane, separated from biogas by available method, because the gas could be liquefied through chilling below -161 0C. This process is adapted by installing the units required when there use of methane separated from biogas as a fuel. Since gas can not be compressed it requires large space for storage.
PERFORMANCE
1. In purification method, by reducing CO2 and moisture along H2S impurities in biogas, the engine performance is improved.
2. Effect of spark timing :-Biogas is slow burning fuel. Hence in order to get optimum engine performance, spark timing does not advance, and then combustion continues in major part of the expansion stroke. This reduces effective work done. By advancing, spark timing power is improved on low speed at partial throttle condition as well as high speed at full throttle condition.
EXHAUST EMMISSIONS
The exhaust emission contains three specific substances which contribute the air pollution, hydrocarbon, carbon monoxide &oxides of nitrogen. Hydrocarbons are the unburned fuel vapour coming out with the exhaust due to incomplete combustion. Hydrocarbon also occurring in crankcase by fuel evaporation. The emission of hydrocarbon is closely related to many design &operating factors like induction system, combustion chamber design, air fuel ratio, speed, load. Lean mixture lower hydrocarbon emission.Carbon monoxide occurs only in engine exhaust.
It is the product of incomplete combustion due to insufficient amount of air in air- fuel mixture. Some amount of CO is always present in the exhaust even at lean mixture. When the throttle is closed to reduce air supply at the time of starting the vehicle, maximum amount of CO is produced. Oxides of nitrogen are the combination of nitric oxide & nitrogen oxide &availability of oxygen are the two main reasons for the formation of oxides of nitrogen. The spark advance means lower peak combustion temperature. It causes high NO concentration in the exhaust. With biogas, co emission levels are low than that of gasoline.
BIT FOR INTELLIGENT SYSTEM DESIGN
The increasing complexity of microelectronic circuitry, as witnessed by multi-chip modules and system-on-a-chip and the rapid growth of manufacturing process automation require, that more effective and efficient testing and fault diagnosis techniques be developed to improve system reliability, reduce system downtime, and esemnhance productivity. As a design philosophy, built-in-test (BIT) is receiving increasing attention from the research community. This paper presents an overview of BIT search in several areas of industry, including semiconductor, manufacturing.
Friday, August 14, 2009
Bolt terminologies and working
Bolt terminologies and working
Introduction:
Bolts are the temporary fastening elements used for assembling of parts. There are 4 models of engines are producing. In these 4 models there are different application, about 40. Maximum torque of 120 Kg-m is required for torquing Main bearing cap bolts of 170 engine model and Connecting rod bolts, Cylinder head bolts, Damper and crank pulley, fly wheel etc. Conventional method of torquing the engine component bolts using manual torque wrench is more operator fatigue and precise control of applied torque is not possible. The difficulties involved in torquing for tightening engine component bolts are listed below.
No fool-proofing arrangementMeasurement of applied torque is not possibleConsuming more Torquing cycle time
Electric Nut Runner is newly emerged torque control fastener tightening tool that is usually powered by Electric power. Electric nut runner mainly consists of 3 components.
They are
1.Spindle
2.Controller
3.Cable
Spindle is equipped with brushless motor and it will tighten the bolt and the spindle is connected to the controller through a cable. Controller receives the feed back signal from the spindle and based on that signal it gives the controlling signal to the spindle. Cable is used to connect both the spindle and controller.
Objective
In the existing method, impact wrench and manual torque wrenches are using for torquing the Main Bearing cap bolts, Cylinder head bolts, Damper and crank pulley, Fly wheel and Fly wheel housing bolts in engine assembly line. In this existing method of bolts torquing cycle time is more and also precise control of torque is not possible.
The objective of proposed work is to study the process requirements and Torquing sequence, mounting height details for Main Bearing cap bolts, Cylinder head bolts, Damper and crank pulley, Fly wheel and Fly wheel housing bolts and propose the Electric Nut Runners spindle and Controller Specifications based on the studied process requirements and torquing sequence, mounting height details to the Manufacturer of Electric Nut Runners.
The Proposed work also includes Installation of 5 Electric Nut Runner in Main Bearing cap bolts, Cylinder head bolts, Damper and crank pulley, Fly wheel and Fly wheel housing stations and 10 pneumatic Nut runners at Selected points in Engine assembly line.
The proposed work also involves calculation of bolts torquing cycle time by Existing Manual Air guns and Pre-calibrated Torque wrench method and by using Proposed Electric and Pneumatic Nut runners Method and to determine how proposed methods are more economical compared to existing process.Finally we discuss here about the working of all the electrical nut runners, there procedure of operation, schematic diagram, and other supportive to nut runners lke PLC programming, Bosch programming.
Scope of the Work:
In six Engine assembly stages namely Main bearing cap bolts, Connecting rod bolts, Cylinder head bolts, Flywheel housing bolts, Flywheel bolts requires high torque with precise control (± 2%). In case of connecting rod bolts in addition to the above, the bolts are to be tightened i.e. “yield to torque”. In these cases number of bolts per engine assembly is ranging from 6 to 36 bolts. With the targeted increase in production levels to 1500 (during 2007-08) the present production practices need to be more reliable and free from operator dependencies.
With enhanced levels of production it is increasingly difficult and practically not possible to achieve a consistent torquing accuracy since the click-type torque wrenches used at present have an accuracy of +/-15%. In this industry, Present practice of pre-torquing using Pneumatic impact wrenches which is followed by manual torquing with pre-calibrated torque wrenches to ensure the final torque consumes lot of time, leave scope for improper torque application apart from need for extra operator to assist while tightening.
The objective of the company is to increase the capacity of the Assembly shop. Thus the primary option is to reduce the Torquing cycle time.Application of Electric and Pneumatic Nut Runners results in reduction in torquing cycle time required for the Assembling of Engine, thus solving the problem of the company.
Scope of project extends to the installation of the electrical nut runners, suitable for all the models, conducting trials to test the feasibility of the nut runners with all the models, check all the sequences, calibration of the nut runners, educating the supervisors, workers so the t they can easily use it.
Bolt Terminology
Helix: The curve formed on any cylinder by a straight line in a plane that is wrapped around the cylinder with a forward progression.
External thread: A thread on the outside of a member. An example is the thread of a bolt
Internal thread: A thread on the inside of a member. An example is the thread inside a nut.
Major diameter: The largest diameter of external or internal threads
Axis: The center line running lengthwise through a screw.
Crest: The surface of the thread corresponding to the major diameter of an external thread and the minor diameter of an internal thread.
Introduction:
Bolts are the temporary fastening elements used for assembling of parts. There are 4 models of engines are producing. In these 4 models there are different application, about 40. Maximum torque of 120 Kg-m is required for torquing Main bearing cap bolts of 170 engine model and Connecting rod bolts, Cylinder head bolts, Damper and crank pulley, fly wheel etc. Conventional method of torquing the engine component bolts using manual torque wrench is more operator fatigue and precise control of applied torque is not possible. The difficulties involved in torquing for tightening engine component bolts are listed below.
No fool-proofing arrangementMeasurement of applied torque is not possibleConsuming more Torquing cycle time
Electric Nut Runner is newly emerged torque control fastener tightening tool that is usually powered by Electric power. Electric nut runner mainly consists of 3 components.
They are
1.Spindle
2.Controller
3.Cable
Spindle is equipped with brushless motor and it will tighten the bolt and the spindle is connected to the controller through a cable. Controller receives the feed back signal from the spindle and based on that signal it gives the controlling signal to the spindle. Cable is used to connect both the spindle and controller.
Objective
In the existing method, impact wrench and manual torque wrenches are using for torquing the Main Bearing cap bolts, Cylinder head bolts, Damper and crank pulley, Fly wheel and Fly wheel housing bolts in engine assembly line. In this existing method of bolts torquing cycle time is more and also precise control of torque is not possible.
The objective of proposed work is to study the process requirements and Torquing sequence, mounting height details for Main Bearing cap bolts, Cylinder head bolts, Damper and crank pulley, Fly wheel and Fly wheel housing bolts and propose the Electric Nut Runners spindle and Controller Specifications based on the studied process requirements and torquing sequence, mounting height details to the Manufacturer of Electric Nut Runners.
The Proposed work also includes Installation of 5 Electric Nut Runner in Main Bearing cap bolts, Cylinder head bolts, Damper and crank pulley, Fly wheel and Fly wheel housing stations and 10 pneumatic Nut runners at Selected points in Engine assembly line.
The proposed work also involves calculation of bolts torquing cycle time by Existing Manual Air guns and Pre-calibrated Torque wrench method and by using Proposed Electric and Pneumatic Nut runners Method and to determine how proposed methods are more economical compared to existing process.Finally we discuss here about the working of all the electrical nut runners, there procedure of operation, schematic diagram, and other supportive to nut runners lke PLC programming, Bosch programming.
Scope of the Work:
In six Engine assembly stages namely Main bearing cap bolts, Connecting rod bolts, Cylinder head bolts, Flywheel housing bolts, Flywheel bolts requires high torque with precise control (± 2%). In case of connecting rod bolts in addition to the above, the bolts are to be tightened i.e. “yield to torque”. In these cases number of bolts per engine assembly is ranging from 6 to 36 bolts. With the targeted increase in production levels to 1500 (during 2007-08) the present production practices need to be more reliable and free from operator dependencies.
With enhanced levels of production it is increasingly difficult and practically not possible to achieve a consistent torquing accuracy since the click-type torque wrenches used at present have an accuracy of +/-15%. In this industry, Present practice of pre-torquing using Pneumatic impact wrenches which is followed by manual torquing with pre-calibrated torque wrenches to ensure the final torque consumes lot of time, leave scope for improper torque application apart from need for extra operator to assist while tightening.
The objective of the company is to increase the capacity of the Assembly shop. Thus the primary option is to reduce the Torquing cycle time.Application of Electric and Pneumatic Nut Runners results in reduction in torquing cycle time required for the Assembling of Engine, thus solving the problem of the company.
Scope of project extends to the installation of the electrical nut runners, suitable for all the models, conducting trials to test the feasibility of the nut runners with all the models, check all the sequences, calibration of the nut runners, educating the supervisors, workers so the t they can easily use it.
Bolt Terminology
Helix: The curve formed on any cylinder by a straight line in a plane that is wrapped around the cylinder with a forward progression.
External thread: A thread on the outside of a member. An example is the thread of a bolt
Internal thread: A thread on the inside of a member. An example is the thread inside a nut.
Major diameter: The largest diameter of external or internal threads
Axis: The center line running lengthwise through a screw.
Crest: The surface of the thread corresponding to the major diameter of an external thread and the minor diameter of an internal thread.
Block Oriented Instrument Software Design
Block Oriented Instrument Software Design
A new method for writing instrumentation software is proposed. It is based on the abstract description of the instrument operation and combines the advantages of a reconfigurable instrument and interchangeability of the instrumentation modules. The proposed test case is the implementation of a microwave network analyzer for nonlinear systems based on VISA and plug and play instrument drivers.
Modern Instruments or Instrumentation setups are likely to be built-up around generic hardware and custom software. The disadvantage is that the amount of software required to operate such a device is very high. An acceptable development time for a reasonably low number of software bugs can therefore only be obtained if the software is maximally reused from earlier developments. Most attempts used a two-step approach. In the first step transport interface between computer and instrument is abstracted. The first step in this approach has always been quite successful. The first transport abstraction stems from the IEEE-488 interface. Afterward SICL and VISA were developed to support multiple transport busses (IEEE-488, RS-232 and later Ethernet and IEE-1394). These methods use a file as the conceptual model for an instrument. The commands sent to the files are independent of the transmission medium, medium dependency is localized only in the initialization call. Most interfaces that can be used for instrumentation control are, hence, supported by these frameworks.
In the second step the instrumentation command is abstracted to empower interchangeability of similar pieces of instrumentation. For this, the situation always has been much less obvious. Only end-users have something to gain in instrument interchangeability. An abstract model to programming instrumentation setups is proposed which is easy and general enough to be used for complex setups.
INTELLIGENT SYSTEM DESIGN
INTELLIGENT SYSTEM DESIGN
The increasing complexity of microelectronic circuitry, as witnessed by multi-chip modules and system-on-a-chip and the rapid growth of manufacturing process automation require, that more effective and efficient testing and fault diagnosis techniques be developed to improve system reliability, reduce system downtime, and esemnhance productivity. As a design philosophy, built-in-test (BIT) is receiving increasing attention from the research community. This paper presents an overview of BIT search in several areas of industry, including semiconductor, manufacturing.
The increasing complexity of microelectronic circuitry, as witnessed by multi-chip modules and system-on-a-chip and the rapid growth of manufacturing process automation require, that more effective and efficient testing and fault diagnosis techniques be developed to improve system reliability, reduce system downtime, and esemnhance productivity. As a design philosophy, built-in-test (BIT) is receiving increasing attention from the research community. This paper presents an overview of BIT search in several areas of industry, including semiconductor, manufacturing.
Wednesday, August 12, 2009
Biomethane
Biomethane
Biomethane is "renewable natural gas" made from organic sources - which starts out as "biogas" but then is cleaned up, removing the impurities in the biogas, such as carbon dioxide and hydrogen sulfide (H2S).
"Cleaned-up" and ready for use in an onsite cogeneration or trigeneration power plant, the Biomethane could also be sold to a pipeline company and completely replace the "natural gas" that is typically transported to markets via the vast underground pipeline system.
Biomethane will some day replace the "methane" that is sold by the local gas companies. Biomethane has an unlimited supply, whereas the methane sold by gas companies has a limited supply. Biomethane is renewable, whereas the methane sold by your gas utility company is not renewable. Biomethane recovery, use and production generates "Greentags" or a "Renewable Energy Credit" for the owners and is GOOD for our environment. The production and use of the natural gas sold by the gas company does NOT generate these incentives and new revenue streams and is NOT good for our environment.
As previously mentioned, Biomethane is "naturally" produced from organic materials as they decay. Sources of Biomethane include; landfills, POTW's/Wastewaster Treatment Systems, and every tree or agricultural product that is no longer living. Biomethane also generated from animal operations where manure can be collected and the Biomethane is generated from anaerobic digesters where the manure decomposes.
Biomethane, after installation of the Biomethane equipment is essentially free, as opposed to buying natural gas, presently costing around $10.00/mmbtu. Methanogenesis, also called Biomethanation, is the production of CH4 and CO2 by biological processes that are carried out by methanogens.
Unlike the price of natural gas, which has been around $6.00/mmbtu to as high as $17.00/mmbtu this past year, Biomethane prices will tend to be more stable over the years as more and more Biomethane is produced, and produced in reliable and sustainable methods that can fuel the energy needs until a better fuel is found.
Biomethane is "renewable natural gas" made from organic sources - which starts out as "biogas" but then is cleaned up, removing the impurities in the biogas, such as carbon dioxide and hydrogen sulfide (H2S).
"Cleaned-up" and ready for use in an onsite cogeneration or trigeneration power plant, the Biomethane could also be sold to a pipeline company and completely replace the "natural gas" that is typically transported to markets via the vast underground pipeline system.
Biomethane will some day replace the "methane" that is sold by the local gas companies. Biomethane has an unlimited supply, whereas the methane sold by gas companies has a limited supply. Biomethane is renewable, whereas the methane sold by your gas utility company is not renewable. Biomethane recovery, use and production generates "Greentags" or a "Renewable Energy Credit" for the owners and is GOOD for our environment. The production and use of the natural gas sold by the gas company does NOT generate these incentives and new revenue streams and is NOT good for our environment.
As previously mentioned, Biomethane is "naturally" produced from organic materials as they decay. Sources of Biomethane include; landfills, POTW's/Wastewaster Treatment Systems, and every tree or agricultural product that is no longer living. Biomethane also generated from animal operations where manure can be collected and the Biomethane is generated from anaerobic digesters where the manure decomposes.
Biomethane, after installation of the Biomethane equipment is essentially free, as opposed to buying natural gas, presently costing around $10.00/mmbtu. Methanogenesis, also called Biomethanation, is the production of CH4 and CO2 by biological processes that are carried out by methanogens.
Unlike the price of natural gas, which has been around $6.00/mmbtu to as high as $17.00/mmbtu this past year, Biomethane prices will tend to be more stable over the years as more and more Biomethane is produced, and produced in reliable and sustainable methods that can fuel the energy needs until a better fuel is found.
Biofuel
Biofuel
Biofuel is defined as solid, liquid or gaseous fuel obtained from relatively recently lifeless biological material and is different from relic fuels, which are derived from long dead biological material. Also, various plants and plant-derived materials are used for biofuel manufacturing.
Globally, biofuels are most commonly used to power vehicles, heat homes, and for cooking. Biofuel industries are expanding in Europe, Asia and the Americas. Recent technology developed at Los Alamos National Lab even allows for the conversion of pollution into renewable bio fuel. Agrofuels are biofuels which are produced from specific crops, rather than from waste processes such as landfill off-gassing or recycled vegetable oil.
There are two common strategies of producing liquid and gaseous agrofuels. One is to grow crops high in sugar (sugar cane, sugar beet, and sweet sorghum) or starch (corn/maize), and then use yeast fermentation to produce ethyl alcohol (ethanol). The second is to grow plants that contain high amounts of vegetable oil, such as oil palm, soybean, algae, jatropha, or pongamia pinnata.
When these oils are heated, their viscosity is reduced, and they can be burned directly in a diesel engine, or they can be chemically processed to produce fuels such as biodiesel. Wood and its byproducts can also be converted into biofuels such as woodgas, methanol or ethanol fuel. It is also possible to make cellulosic ethanol from non-edible plant parts, but this can be difficult to accomplish economically.
Biofuel is defined as solid, liquid or gaseous fuel obtained from relatively recently lifeless biological material and is different from relic fuels, which are derived from long dead biological material. Also, various plants and plant-derived materials are used for biofuel manufacturing.
Globally, biofuels are most commonly used to power vehicles, heat homes, and for cooking. Biofuel industries are expanding in Europe, Asia and the Americas. Recent technology developed at Los Alamos National Lab even allows for the conversion of pollution into renewable bio fuel. Agrofuels are biofuels which are produced from specific crops, rather than from waste processes such as landfill off-gassing or recycled vegetable oil.
There are two common strategies of producing liquid and gaseous agrofuels. One is to grow crops high in sugar (sugar cane, sugar beet, and sweet sorghum) or starch (corn/maize), and then use yeast fermentation to produce ethyl alcohol (ethanol). The second is to grow plants that contain high amounts of vegetable oil, such as oil palm, soybean, algae, jatropha, or pongamia pinnata.
When these oils are heated, their viscosity is reduced, and they can be burned directly in a diesel engine, or they can be chemically processed to produce fuels such as biodiesel. Wood and its byproducts can also be converted into biofuels such as woodgas, methanol or ethanol fuel. It is also possible to make cellulosic ethanol from non-edible plant parts, but this can be difficult to accomplish economically.
Types of Bio Fuels
Types of Bio Fuels
First generation biofuels'First-generation biofuels' are biofuels made from sugar, starch, vegetable oil, or animal fats using conventional technology. The basic feedstocks for the production of first generation biofuels are often seeds or grains such as wheat, which yields starch that is fermented into bioethanol, or sunflower seeds, which are pressed to yield vegetable oil that can be used in biodiesel. These feedstocks could instead enter the animal or human food chain, and as the global population has risen their use in producing biofuels has been criticised for diverting food away from the human food chain, leading to food shortages and price rises.
The most common first generation biofuels are listed below.
Vegetable oilMain article:
Vegetable oil used as fuelEdible vegetable oil is generally not used as fuel, but lower quality oil can be used for this purpose. Used vegetable oil is increasingly being processed into biodiesel, or (more rarely) cleaned of water and particulates and used as a fuel. To ensure that the fuel injectors atomize the fuel in the correct pattern for efficient combustion, vegetable oil fuel must be heated to reduce its viscosity to that of diesel, either by electric coils or heat exchangers. This is easier in warm or temperate climates. MAN B&W Diesel, Wartsila and Deutz AG offer engines that are compatible with straight vegetable oil, without the need for after-market modifications. Vegetable oil can also be used in many older diesel engines that do not use common rail or unit injection electronic diesel injection systems. Due to the design of the combustion chambers in indirect injection engines, these are the best engines for use with vegetable oil.
This system allows the relatively larger oil molecules more time to burn. However, a handful of drivers have experienced limited success with earlier pre-"pumped use" VW TDI engines and other similar engines with direct injection.BiodieselMain articles: Biodiesel and Biodiesel around the worldBiodiesel is the most common biofuel in Europe. It is produced from oils or fats using transesterification and is a liquid similar in composition to fossil/mineral diesel. Its chemical name is fatty acid methyl (or ethyl) ester (FAME). Oils are mixed with sodium hydroxide and methanol (or ethanol) and the chemical reaction produces biodiesel (FAME) and glycerol. One part glycerol is produced for every 10 parts biodiesel. Feedstocks for biodiesel include animal fats, vegetable oils, soy, rapeseed, jatropha, mahua, mustard, flax, sunflower, palm oil, hemp, field pennycress, pongamia pinnata and algae. Pure biodiesel (B100) is by far the lowest emission diesel fuel.
Although liquefied petroleum gas and hydrogen have cleaner combustion, they are used to fuel much less efficient petrol engines and are not as widely available.Biodiesel can be used in any diesel engine when mixed with mineral diesel.
The majority of vehicle manufacturers limit their recommendations to 15% biodiesel blended with mineral diesel. In some countries manufacturers cover their diesel engines under warranty for B100 use, although Volkswagen of Germany, for example, asks drivers to check by telephone with the VW environmental services department before switching to B100. B100 may become more viscous at lower temperatures, depending on the feedstock used, requiring vehicles to have fuel line heaters.
In most cases, biodiesel is compatible with diesel engines from 1994 onwards, which use 'Viton' (by DuPont) synthetic rubber in their mechanical injection systems. Electronically controlled 'common rail' and 'pump duse' type systems from the late 1990s onwards may only use biodiesel blended with conventional diesel fuel. These engines have finely metered and atomized multi-stage injection systems are very sensitive to the viscosity of the fuel. Many current generation diesel engines are made so that they can run on B100 without altering the engine itself, although this depends on the fuel rail design. NExBTL is suitable for all diesel engines in the world since it overperforms DIN EN 590 standards.Since biodiesel is an effective solvent and cleans residues deposited by mineral diesel, engine filters may need to be replaced more often, as the biofuel dissolves old deposits in the fuel tank and pipes.
It also effectively cleans the engine combustion chamber of carbon deposits, helping to maintain efficiency. In many European countries, a 5% biodiesel blend is widely used and is available at thousands of gas stations. Biodiesel is also an oxygenated fuel, meaning that it contains a reduced amount of carbon and higher hydrogen and oxygen content than fossil diesel. This improves the combustion of fossil diesel and reduces the particulate emissions from un-burnt carbon.In the USA, more than 80% of commercial trucks and city buses run on diesel. The emerging US biodiesel market is estimated to have grown 200% from 2004 to 2005. "By the end of 2006 biodiesel production was estimated to increase fourfold [from 2004] to more than 1 billion gallons.
BioalcoholsBiologically produced alcohols, most commonly ethanol, and less commonly propanol and butanol, are produced by the action of microorganisms and enzymes through the fermentation of sugars or starches (easiest), or cellulose (which is more difficult). Biobutanol (also called biogasoline) is often claimed to provide a direct replacement for gasoline, because it can be used directly in a gasoline engine (in a similar way to biodiesel in diesel engines).Butanol is formed by ABE fermentation (acetone, butanol, ethanol) and experimental modifications of the process show potentially high net energy gains with butanol as the only liquid product. Butanol will produce more energy and allegedly can be burned "straight" in existing gasoline engines (without modification to the engine or car), and is less corrosive and less water soluble than ethanol, and could be distributed via existing infrastructures. DuPont and BP are working together to help develop Butanol. E. coli have also been successfully engineered to produce Butanol by hijacking their amino acid metabolism.Ethanol fuel is the most common biofuel worldwide, particularly in Brazil. Alcohol fuels are produced by fermentation of sugars derived from wheat, corn, sugar beets, sugar cane, molasses and any sugar or starch that alcoholic beverages can be made from (like potato and fruit waste, etc.). The ethanol production methods used are enzyme digestion (to release sugars from stored starches, fermentation of the sugars, distillation and drying. The distillation process requires significant energy input for heat (often unsustainable natural gas fossil fuel, but cellulosic biomass such as bagasse, the waste left after sugar cane is pressed to extract its juice, can also be used more sustainably).Ethanol can be used in petrol engines as a replacement for gasoline; it can be mixed with gasoline to any percentage. Most existing automobile petrol engines can run on blends of up to 15% bioethanol with petroleum/gasoline. Gasoline with ethanol added has higher octane, which means that your engine can typically burn hotter and more efficiently. In high altitude (thin air) locations, some states mandate a mix of gasoline and ethanol as a winter oxidizer to reduce atmospheric pollution emissions.Ethanol fuel has less BTU energy content, which means it takes more fuel (volume and mass) to produce the same amount of work. An advantage of ethanol is that is has a higher octane rating than ethanol-free gasoline available at roadside gas stations and ethanol's higher octane rating allows an increase of an engine's compression ratio for increased thermal efficiency.. Very-expensive aviation gasoline (Avgas) is 100 octane made from 100% petroleum with toxic tetra-ethyl lead added to raise the octane number. The high price of zero-ethanol Avgas does not include federal-and-state road-use taxes.Ethanol is very corrosive to fuel systems, rubber hoses and gaskets, aluminum, and combustion chambers. Therefore, it is illegal to use fuels containing alcohol in aircraft (although at least one model of ethanol-powered aircraft has been developed, the Embraer EMB 202 Ipanema). Ethanol also corrodes fiberglass fuel tanks such as used in marine engines. For higher ethanol percentage blends, and 100% ethanol vehicles, engine modifications are required.It is the hygroscopic (water loving) nature of relatively polar ethanol that can promote corrosion of existing pipelines and older fuel delivery systems. To characterize ethanol itself as a corrosive chemical is somewhat misleading and the context in which it can be indirectly corrosive, somewhat narrow; i.e., limited to effects upon existing pipelines designed for petroleum transport.Corrosive ethanol cannot be transported in petroleum pipelines, so more-expensive over-the-road stainless-steel tank trucks increase the cost and energy consumption required to deliver ethanol to the customer at the pump.In the current alcohol-from-corn production model in the United States, considering the total energy consumed by farm equipment, cultivation, planting, fertilizers, pesticides, herbicides, and fungicides made from petroleum, irrigation systems, harvesting, transport of feedstock to processing plants, fermentation, distillation, drying, transport to fuel terminals and retail pumps, and lower ethanol fuel energy content, the net energy content value added and delivered to consumers is very small. And, the net benefit (all things considered) does little to reduce un-sustainable imported oil and fossil fuels required to produce the ethanol.Although ethanol-from-corn and other food stocks has implications both in terms of world food prices and limited, yet positive energy yield (in terms of energy delivered to customer/fossil fuels used), the technology has lead to the development of cellulosic ethanol. According to a joint research agenda conducted through the U.S. Department of Energy, the fossil energy ratios (FER) for cellulosic ethanol, corn ethanol, and gasoline are 10.3, 1.36, and 0.81, respectively.Many car manufacturers are now producing flexible-fuel vehicles (FFV's), which can safely run on any combination of bioethanol and petrol, up to 100% bioethanol. They dynamically sense exhaust oxygen content, and adjust the engine's computer systems, spark, and fuel injection accordingly. This adds initial cost and ongoing increased vehicle maintenance. Efficiency falls and pollution emissions increase when FFV system maintenance is needed (regardless of the fuel mix being used), but not performed (as with all vehicles). FFV internal combustion engines are becoming increasingly complex, as are multiple-propulsion-system FFV hybrid vehicles, which impacts cost, maintenance, reliability, and useful lifetime longevity.Alcohol mixes with both petroleum and with water, so ethanol fuels are often diluted after the drying process by absorbing environmental moisture from the atmosphere. Water in alcohol-mix fuels reduces efficiency, makes engines harder to start, causes intermittent operation (sputtering), and oxidizes aluminum (carburetors) and steel components (rust).Even dry ethanol has roughly one-third lower energy content per unit of volume compared to gasoline, so larger / heavier fuel tanks are required to travel the same distance, or more fuel stops are required. With large current un-sustainable, non-scalable subsidies, ethanol fuel still costs much more per distance traveled than current high gasoline prices in the United States.Methanol is currently produced from natural gas, a non-renewable fossil fuel. It can also be produced from biomass as biomethanol. The methanol economy is an interesting alternative to the hydrogen economy, compared to today's hydrogen produced from natural gas, but not hydrogen production directly from water and state-of-the-art clean solar thermal energy processes.BioethersBio ethers (also referred to as fuel ethers or fuel oxygenates) are cost-effective compounds that act as octane enhancers. They also enhance engine performance, whilst significantly reducing engine wear and toxic exhaust emissions. Greatly reducing the amount of ground-level ozone, they contribute to the quality of the air we breathe.Biogas is produced by the process of anaerobic digestion of organic material by anaerobes. It can be produced either from biodegradable waste materials or by the use of energy crops fed into anaerobic digesters to supplement gas yields. The solid byproduct, digestate, can be used as a biofuel or a fertilizer. In the UK, the National Coal Board experimented with microorganisms that digested coal in situ converting it directly to gases such as methane.Biogas contains methane and can be recovered from industrial anaerobic digesters and mechanical biological treatment systems. Landfill gas is a less clean form of biogas which is produced in landfills through naturally occurring anaerobic digestion. If it escapes into the atmosphere it is a potent greenhouse gas.Oils and gases can be produced from various biological wastes:• Thermal depolymerization of waste can extract methane and other oils similar to petroleum.• GreenFuel Technologies Corporation developed a patented bioreactor system that uses nontoxic photosynthetic algae to take in smokestacks flue gases and produce biofuels such as biodiesel, biogas and a dry fuel comparable to coal.SyngasMain article: GasificationSyngas, a mixture of carbon monoxide and hydrogen, is produced by partial combustion of biomass, that is, combustion with an amount of oxygen that is not sufficient to convert the biomass completely to carbon dioxide and water. Before partial combustion the biomass is dried, and sometimes pyrolysed.The resulting gas mixture, syngas, is itself a fuel. Using the syngas is more efficient than direct combustion of the original biofuel; more of the energy contained in the fuel is extracted.Syngas may be burned directly in internal combustion engines or turbines. The wood gas generator is a wood-fueled gasification reactor mounted on an internal combustion engine. Syngas can be used to produce methanol and hydrogen, or converted via the Fischer-Tropsch process to produce a synthetic diesel substitute, or a mixture of alcohols that can be blended into gasoline. Gasification normally relies on temperatures >700°C. Lower temperature gasification is desirable when co-producing biochar but results in a Syngas polluted with tar.Solid biofuelsExamples include wood, sawdust, grass cuttings, domestic refuse, charcoal, agricultural waste, non-food energy crops (see picture), and dried manure.When raw biomass is already in a suitable form (such as firewood), it can burn directly in a stove or furnace to provide heat or raise steam. When raw biomass is in an inconvenient form (such as sawdust, wood chips, grass, agricultural wastes), another option is to pelletize the biomass with a pellet mill. The resulting fuel pellets are easier to burn in a pellet stove.A problem with the combustion of raw biomass is that it emits considerable amounts of pollutants such as particulates and PAHs (polycyclic aromatic hydrocarbons). Even modern pellet boilers generates much more pollutants than oil or natural gas boilers. Pellets made from agricultural residues are usually worse than wood pellets, producing much larger emissions of dioxins and chlorophenols.Another solid biofuel is biochar, which is produced by biomass pyrolysis. Biochar pellets made from agricultural waste can substitute for wood charcoal. In countries where charcoal stoves are popular, this can reduce deforestation.Second generation biofuelsSupporters of biofuels claim that a more viable solution is to increase political and industrial support for, and rapidity of, second-generation biofuel implementation from non food crops, including cellulosic biofuels. Second-generation biofuel production processes can use a variety of non food crops. These include waste biomass, the stalks of wheat, corn, wood, and special-energy-or-biomass crops (e.g. Miscanthus). Second generation (2G) biofuels use biomass to liquid technology, including cellulosic biofuels from non food crops. Many second generation biofuels are under development such as biohydrogen, biomethanol, DMF, Bio-DME, Fischer-Tropsch diesel, biohydrogen diesel, mixed alcohols and wood diesel.Cellulosic ethanol production uses non food crops or inedible waste products and does not divert food away from the animal or human food chain. Lignocellulose is the "woody" structural material of plants. This feedstock is abundant and diverse, and in some cases (like citrus peels or sawdust) it is a significant disposal problem.Producing ethanol from cellulose is a difficult technical problem to solve. In nature, ruminant livestock (like cattle) eats grass and then use slow enzymatic digestive processes to break it into glucose (sugar). In cellulosic ethanol laboratories, various experimental processes are being developed to do the same thing, and then the sugars released can be fermented to make ethanol fuel. In 2009 scientists reported developing, using "synthetic biology", "15 new highly stable fungal enzyme catalysts that efficiently break down cellulose into sugars at high temperatures", adding to the 10 previously known. In addition, research conducted at TU Delft by Jack Pronk has shown that elephant yeast, when slightly modified can also create ethanol from non-edible ground sources (eg straw).The recent discovery of the fungus Gliocladium roseum points toward the production of so-called myco-diesel from cellulose. This organism was recently discovered in the rainforests of northern Patagonia and has the unique capability of converting cellulose into medium length hydrocarbons typically found in diesel fuel.Scientists also work on experimental recombinant DNA genetic engineering organisms that could increase biofuel potential.Third generation biofuelsAlgae fuelAlgae fuel, also called oilgae or third generation biofuel, is a biofuel from algae. Algae are low-input, high-yield feedstocks to produce biofuels. It produces 30 times more energy per acre than land crops such as soybeans. With the higher prices of fossil fuels (petroleum), there is much interest in algaculture (farming algae). One advantage of many biofuels over most other fuel types is that they are biodegradable, and so relatively harmless to the environment if spilled.The United States Department of Energy estimates that if algae fuel replaced all the petroleum fuel in the United States, it would require 15,000 square miles (38,849 square kilometers), which is roughly the size of Maryland.Second and third generation biofuels are also called advanced biofuels.Algae, such as Botryococcus braunii and Chlorella vulgaris, are relatively easy to grow, but the algal oil is hard to extract. There are several approaches, some of which work better than others. See: Prospects for the Biodiesel Industry.Biofuels by regionMain article: Biofuels by regionRecognizing the importance of implementing bioenergy, there are international organizations such as IEA Bioenergy, established in 1978 by the OECD International Energy Agency (IEA), with the aim of improving cooperation and information exchange between countries that have national programs in bioenergy research, development and deployment. The U.N. International Biofuels Forum is formed by Brazil, China, India, South Africa, the United States and the European Commission. The world leaders in biofuel development and use are Brazil, United States, France, Sweden and Germany
First generation biofuels'First-generation biofuels' are biofuels made from sugar, starch, vegetable oil, or animal fats using conventional technology. The basic feedstocks for the production of first generation biofuels are often seeds or grains such as wheat, which yields starch that is fermented into bioethanol, or sunflower seeds, which are pressed to yield vegetable oil that can be used in biodiesel. These feedstocks could instead enter the animal or human food chain, and as the global population has risen their use in producing biofuels has been criticised for diverting food away from the human food chain, leading to food shortages and price rises.
The most common first generation biofuels are listed below.
Vegetable oilMain article:
Vegetable oil used as fuelEdible vegetable oil is generally not used as fuel, but lower quality oil can be used for this purpose. Used vegetable oil is increasingly being processed into biodiesel, or (more rarely) cleaned of water and particulates and used as a fuel. To ensure that the fuel injectors atomize the fuel in the correct pattern for efficient combustion, vegetable oil fuel must be heated to reduce its viscosity to that of diesel, either by electric coils or heat exchangers. This is easier in warm or temperate climates. MAN B&W Diesel, Wartsila and Deutz AG offer engines that are compatible with straight vegetable oil, without the need for after-market modifications. Vegetable oil can also be used in many older diesel engines that do not use common rail or unit injection electronic diesel injection systems. Due to the design of the combustion chambers in indirect injection engines, these are the best engines for use with vegetable oil.
This system allows the relatively larger oil molecules more time to burn. However, a handful of drivers have experienced limited success with earlier pre-"pumped use" VW TDI engines and other similar engines with direct injection.BiodieselMain articles: Biodiesel and Biodiesel around the worldBiodiesel is the most common biofuel in Europe. It is produced from oils or fats using transesterification and is a liquid similar in composition to fossil/mineral diesel. Its chemical name is fatty acid methyl (or ethyl) ester (FAME). Oils are mixed with sodium hydroxide and methanol (or ethanol) and the chemical reaction produces biodiesel (FAME) and glycerol. One part glycerol is produced for every 10 parts biodiesel. Feedstocks for biodiesel include animal fats, vegetable oils, soy, rapeseed, jatropha, mahua, mustard, flax, sunflower, palm oil, hemp, field pennycress, pongamia pinnata and algae. Pure biodiesel (B100) is by far the lowest emission diesel fuel.
Although liquefied petroleum gas and hydrogen have cleaner combustion, they are used to fuel much less efficient petrol engines and are not as widely available.Biodiesel can be used in any diesel engine when mixed with mineral diesel.
The majority of vehicle manufacturers limit their recommendations to 15% biodiesel blended with mineral diesel. In some countries manufacturers cover their diesel engines under warranty for B100 use, although Volkswagen of Germany, for example, asks drivers to check by telephone with the VW environmental services department before switching to B100. B100 may become more viscous at lower temperatures, depending on the feedstock used, requiring vehicles to have fuel line heaters.
In most cases, biodiesel is compatible with diesel engines from 1994 onwards, which use 'Viton' (by DuPont) synthetic rubber in their mechanical injection systems. Electronically controlled 'common rail' and 'pump duse' type systems from the late 1990s onwards may only use biodiesel blended with conventional diesel fuel. These engines have finely metered and atomized multi-stage injection systems are very sensitive to the viscosity of the fuel. Many current generation diesel engines are made so that they can run on B100 without altering the engine itself, although this depends on the fuel rail design. NExBTL is suitable for all diesel engines in the world since it overperforms DIN EN 590 standards.Since biodiesel is an effective solvent and cleans residues deposited by mineral diesel, engine filters may need to be replaced more often, as the biofuel dissolves old deposits in the fuel tank and pipes.
It also effectively cleans the engine combustion chamber of carbon deposits, helping to maintain efficiency. In many European countries, a 5% biodiesel blend is widely used and is available at thousands of gas stations. Biodiesel is also an oxygenated fuel, meaning that it contains a reduced amount of carbon and higher hydrogen and oxygen content than fossil diesel. This improves the combustion of fossil diesel and reduces the particulate emissions from un-burnt carbon.In the USA, more than 80% of commercial trucks and city buses run on diesel. The emerging US biodiesel market is estimated to have grown 200% from 2004 to 2005. "By the end of 2006 biodiesel production was estimated to increase fourfold [from 2004] to more than 1 billion gallons.
BioalcoholsBiologically produced alcohols, most commonly ethanol, and less commonly propanol and butanol, are produced by the action of microorganisms and enzymes through the fermentation of sugars or starches (easiest), or cellulose (which is more difficult). Biobutanol (also called biogasoline) is often claimed to provide a direct replacement for gasoline, because it can be used directly in a gasoline engine (in a similar way to biodiesel in diesel engines).Butanol is formed by ABE fermentation (acetone, butanol, ethanol) and experimental modifications of the process show potentially high net energy gains with butanol as the only liquid product. Butanol will produce more energy and allegedly can be burned "straight" in existing gasoline engines (without modification to the engine or car), and is less corrosive and less water soluble than ethanol, and could be distributed via existing infrastructures. DuPont and BP are working together to help develop Butanol. E. coli have also been successfully engineered to produce Butanol by hijacking their amino acid metabolism.Ethanol fuel is the most common biofuel worldwide, particularly in Brazil. Alcohol fuels are produced by fermentation of sugars derived from wheat, corn, sugar beets, sugar cane, molasses and any sugar or starch that alcoholic beverages can be made from (like potato and fruit waste, etc.). The ethanol production methods used are enzyme digestion (to release sugars from stored starches, fermentation of the sugars, distillation and drying. The distillation process requires significant energy input for heat (often unsustainable natural gas fossil fuel, but cellulosic biomass such as bagasse, the waste left after sugar cane is pressed to extract its juice, can also be used more sustainably).Ethanol can be used in petrol engines as a replacement for gasoline; it can be mixed with gasoline to any percentage. Most existing automobile petrol engines can run on blends of up to 15% bioethanol with petroleum/gasoline. Gasoline with ethanol added has higher octane, which means that your engine can typically burn hotter and more efficiently. In high altitude (thin air) locations, some states mandate a mix of gasoline and ethanol as a winter oxidizer to reduce atmospheric pollution emissions.Ethanol fuel has less BTU energy content, which means it takes more fuel (volume and mass) to produce the same amount of work. An advantage of ethanol is that is has a higher octane rating than ethanol-free gasoline available at roadside gas stations and ethanol's higher octane rating allows an increase of an engine's compression ratio for increased thermal efficiency.. Very-expensive aviation gasoline (Avgas) is 100 octane made from 100% petroleum with toxic tetra-ethyl lead added to raise the octane number. The high price of zero-ethanol Avgas does not include federal-and-state road-use taxes.Ethanol is very corrosive to fuel systems, rubber hoses and gaskets, aluminum, and combustion chambers. Therefore, it is illegal to use fuels containing alcohol in aircraft (although at least one model of ethanol-powered aircraft has been developed, the Embraer EMB 202 Ipanema). Ethanol also corrodes fiberglass fuel tanks such as used in marine engines. For higher ethanol percentage blends, and 100% ethanol vehicles, engine modifications are required.It is the hygroscopic (water loving) nature of relatively polar ethanol that can promote corrosion of existing pipelines and older fuel delivery systems. To characterize ethanol itself as a corrosive chemical is somewhat misleading and the context in which it can be indirectly corrosive, somewhat narrow; i.e., limited to effects upon existing pipelines designed for petroleum transport.Corrosive ethanol cannot be transported in petroleum pipelines, so more-expensive over-the-road stainless-steel tank trucks increase the cost and energy consumption required to deliver ethanol to the customer at the pump.In the current alcohol-from-corn production model in the United States, considering the total energy consumed by farm equipment, cultivation, planting, fertilizers, pesticides, herbicides, and fungicides made from petroleum, irrigation systems, harvesting, transport of feedstock to processing plants, fermentation, distillation, drying, transport to fuel terminals and retail pumps, and lower ethanol fuel energy content, the net energy content value added and delivered to consumers is very small. And, the net benefit (all things considered) does little to reduce un-sustainable imported oil and fossil fuels required to produce the ethanol.Although ethanol-from-corn and other food stocks has implications both in terms of world food prices and limited, yet positive energy yield (in terms of energy delivered to customer/fossil fuels used), the technology has lead to the development of cellulosic ethanol. According to a joint research agenda conducted through the U.S. Department of Energy, the fossil energy ratios (FER) for cellulosic ethanol, corn ethanol, and gasoline are 10.3, 1.36, and 0.81, respectively.Many car manufacturers are now producing flexible-fuel vehicles (FFV's), which can safely run on any combination of bioethanol and petrol, up to 100% bioethanol. They dynamically sense exhaust oxygen content, and adjust the engine's computer systems, spark, and fuel injection accordingly. This adds initial cost and ongoing increased vehicle maintenance. Efficiency falls and pollution emissions increase when FFV system maintenance is needed (regardless of the fuel mix being used), but not performed (as with all vehicles). FFV internal combustion engines are becoming increasingly complex, as are multiple-propulsion-system FFV hybrid vehicles, which impacts cost, maintenance, reliability, and useful lifetime longevity.Alcohol mixes with both petroleum and with water, so ethanol fuels are often diluted after the drying process by absorbing environmental moisture from the atmosphere. Water in alcohol-mix fuels reduces efficiency, makes engines harder to start, causes intermittent operation (sputtering), and oxidizes aluminum (carburetors) and steel components (rust).Even dry ethanol has roughly one-third lower energy content per unit of volume compared to gasoline, so larger / heavier fuel tanks are required to travel the same distance, or more fuel stops are required. With large current un-sustainable, non-scalable subsidies, ethanol fuel still costs much more per distance traveled than current high gasoline prices in the United States.Methanol is currently produced from natural gas, a non-renewable fossil fuel. It can also be produced from biomass as biomethanol. The methanol economy is an interesting alternative to the hydrogen economy, compared to today's hydrogen produced from natural gas, but not hydrogen production directly from water and state-of-the-art clean solar thermal energy processes.BioethersBio ethers (also referred to as fuel ethers or fuel oxygenates) are cost-effective compounds that act as octane enhancers. They also enhance engine performance, whilst significantly reducing engine wear and toxic exhaust emissions. Greatly reducing the amount of ground-level ozone, they contribute to the quality of the air we breathe.Biogas is produced by the process of anaerobic digestion of organic material by anaerobes. It can be produced either from biodegradable waste materials or by the use of energy crops fed into anaerobic digesters to supplement gas yields. The solid byproduct, digestate, can be used as a biofuel or a fertilizer. In the UK, the National Coal Board experimented with microorganisms that digested coal in situ converting it directly to gases such as methane.Biogas contains methane and can be recovered from industrial anaerobic digesters and mechanical biological treatment systems. Landfill gas is a less clean form of biogas which is produced in landfills through naturally occurring anaerobic digestion. If it escapes into the atmosphere it is a potent greenhouse gas.Oils and gases can be produced from various biological wastes:• Thermal depolymerization of waste can extract methane and other oils similar to petroleum.• GreenFuel Technologies Corporation developed a patented bioreactor system that uses nontoxic photosynthetic algae to take in smokestacks flue gases and produce biofuels such as biodiesel, biogas and a dry fuel comparable to coal.SyngasMain article: GasificationSyngas, a mixture of carbon monoxide and hydrogen, is produced by partial combustion of biomass, that is, combustion with an amount of oxygen that is not sufficient to convert the biomass completely to carbon dioxide and water. Before partial combustion the biomass is dried, and sometimes pyrolysed.The resulting gas mixture, syngas, is itself a fuel. Using the syngas is more efficient than direct combustion of the original biofuel; more of the energy contained in the fuel is extracted.Syngas may be burned directly in internal combustion engines or turbines. The wood gas generator is a wood-fueled gasification reactor mounted on an internal combustion engine. Syngas can be used to produce methanol and hydrogen, or converted via the Fischer-Tropsch process to produce a synthetic diesel substitute, or a mixture of alcohols that can be blended into gasoline. Gasification normally relies on temperatures >700°C. Lower temperature gasification is desirable when co-producing biochar but results in a Syngas polluted with tar.Solid biofuelsExamples include wood, sawdust, grass cuttings, domestic refuse, charcoal, agricultural waste, non-food energy crops (see picture), and dried manure.When raw biomass is already in a suitable form (such as firewood), it can burn directly in a stove or furnace to provide heat or raise steam. When raw biomass is in an inconvenient form (such as sawdust, wood chips, grass, agricultural wastes), another option is to pelletize the biomass with a pellet mill. The resulting fuel pellets are easier to burn in a pellet stove.A problem with the combustion of raw biomass is that it emits considerable amounts of pollutants such as particulates and PAHs (polycyclic aromatic hydrocarbons). Even modern pellet boilers generates much more pollutants than oil or natural gas boilers. Pellets made from agricultural residues are usually worse than wood pellets, producing much larger emissions of dioxins and chlorophenols.Another solid biofuel is biochar, which is produced by biomass pyrolysis. Biochar pellets made from agricultural waste can substitute for wood charcoal. In countries where charcoal stoves are popular, this can reduce deforestation.Second generation biofuelsSupporters of biofuels claim that a more viable solution is to increase political and industrial support for, and rapidity of, second-generation biofuel implementation from non food crops, including cellulosic biofuels. Second-generation biofuel production processes can use a variety of non food crops. These include waste biomass, the stalks of wheat, corn, wood, and special-energy-or-biomass crops (e.g. Miscanthus). Second generation (2G) biofuels use biomass to liquid technology, including cellulosic biofuels from non food crops. Many second generation biofuels are under development such as biohydrogen, biomethanol, DMF, Bio-DME, Fischer-Tropsch diesel, biohydrogen diesel, mixed alcohols and wood diesel.Cellulosic ethanol production uses non food crops or inedible waste products and does not divert food away from the animal or human food chain. Lignocellulose is the "woody" structural material of plants. This feedstock is abundant and diverse, and in some cases (like citrus peels or sawdust) it is a significant disposal problem.Producing ethanol from cellulose is a difficult technical problem to solve. In nature, ruminant livestock (like cattle) eats grass and then use slow enzymatic digestive processes to break it into glucose (sugar). In cellulosic ethanol laboratories, various experimental processes are being developed to do the same thing, and then the sugars released can be fermented to make ethanol fuel. In 2009 scientists reported developing, using "synthetic biology", "15 new highly stable fungal enzyme catalysts that efficiently break down cellulose into sugars at high temperatures", adding to the 10 previously known. In addition, research conducted at TU Delft by Jack Pronk has shown that elephant yeast, when slightly modified can also create ethanol from non-edible ground sources (eg straw).The recent discovery of the fungus Gliocladium roseum points toward the production of so-called myco-diesel from cellulose. This organism was recently discovered in the rainforests of northern Patagonia and has the unique capability of converting cellulose into medium length hydrocarbons typically found in diesel fuel.Scientists also work on experimental recombinant DNA genetic engineering organisms that could increase biofuel potential.Third generation biofuelsAlgae fuelAlgae fuel, also called oilgae or third generation biofuel, is a biofuel from algae. Algae are low-input, high-yield feedstocks to produce biofuels. It produces 30 times more energy per acre than land crops such as soybeans. With the higher prices of fossil fuels (petroleum), there is much interest in algaculture (farming algae). One advantage of many biofuels over most other fuel types is that they are biodegradable, and so relatively harmless to the environment if spilled.The United States Department of Energy estimates that if algae fuel replaced all the petroleum fuel in the United States, it would require 15,000 square miles (38,849 square kilometers), which is roughly the size of Maryland.Second and third generation biofuels are also called advanced biofuels.Algae, such as Botryococcus braunii and Chlorella vulgaris, are relatively easy to grow, but the algal oil is hard to extract. There are several approaches, some of which work better than others. See: Prospects for the Biodiesel Industry.Biofuels by regionMain article: Biofuels by regionRecognizing the importance of implementing bioenergy, there are international organizations such as IEA Bioenergy, established in 1978 by the OECD International Energy Agency (IEA), with the aim of improving cooperation and information exchange between countries that have national programs in bioenergy research, development and deployment. The U.N. International Biofuels Forum is formed by Brazil, China, India, South Africa, the United States and the European Commission. The world leaders in biofuel development and use are Brazil, United States, France, Sweden and Germany
Bioenergy
Bioenergy
Bioenergy is renewable energy made available from materials derived from biological sources. In its most narrow sense it is a synonym to biofuel, which is fuel derived from biological sources. In its broader sense it includes biomass, the biological material used as a biofuel, as well as the social, economic, scientific and technical fields associated with using biological sources for energy. This is a common misconception, as bioenergy is the energy extracted from the biomass, as the biomass is the fuel and the bioenergy is the energy contained in the fuel.
Biomass is any organic material which has stored sunlight in the form of chemical energy. As a fuel it may include wood, wood waste, straw, manure, sugar cane, and many other byproducts from a variety of agricultural processes.
There is a slight tendency for the word bioenergy to be favoured in Europe compared with biofuel in North America.
Solid Biomass
Biomass is material derived from recently living organisms, which includes plants, animals and their byproducts. Manure, garden waste and crop residues are all sources of biomass. It is a renewable energy source based on the carbon cycle, unlike other natural resources such as petroleum, coal, and nuclear fuels.
Animal waste is a persistent and unavoidable pollutant produced primarily by the animals housed in industrial-sized farms.
There are also agricultural products being grown for biofuel production. These include corn, switchgrass, and soybeans, primarily in the United States; rapeseed, wheat and sugar beet primarily in Europe; sugar cane in Brazil; palm oil and miscanthus in Southeast Asia; sorghum and cassava in China; and jatropha in India. Hemp has also been proven to work as a biofuel. Biodegradable outputs from industry, agriculture, forestry and households can be used for biofuel production, using e.g. anaerobic digestion to produce biogas, gasification to produce syngas or by direct combustion. Examples of biodegradable wastes include straw, timber, manure, rice husks, sewage, and food waste. The use of biomass fuels can therefore contribute to waste management as well as fuel security and help to prevent or slow down climate change, although alone they are not a comprehensive solution to these problems.
Electricity generation from biomass
Electricity from sugarcane bagasse in Brazil
Sugar/Ethanol Plant located in Piracicaba, São Paulo State. This plant produces the electricity it needs from baggasse residuals from sugarcane left over by the milling process, and it sells the surplus electricity to the public grid.
Sucrose accounts for little more than 30% of the chemical energy stored in the mature plant; 35% is in the leaves and stem tips, which are left in the fields during harvest, and 35% are in the fibrous material (bagasse) left over from pressing.
The production process of sugar and ethanol in Brazil takes full advantage of the energy stored in sugarcane. Part of the baggasse is currently burned at the mill to provide heat for distillation and electricity to run the machinery. This allows ethanol plants to be energetically self-sufficient and even sell surplus electricity to utilities; current production is 600 MW for self-use and 100 MW for sale. This secondary activity is expected to boom now that utilities have been induced to pay "fair price "(about US$10/GJ or US$0.036/kWh) for 10 year contracts. This is approximately half of what the World Bank considers the reference price for investing in similar projects (see below). The energy is especially valuable to utilities because it is produced mainly in the dry season when hydroelectric dams are running low. Estimates of potential power generation from bagasse range from 1,000 to 9,000 MW, depending on technology. Higher estimates assume gasification of biomass, replacement of current low-pressure steam boilers and turbines by high-pressure ones, and use of harvest trash currently left behind in the fields. For comparison, Brazil's Angra I nuclear plant generates 657 MW.
Presently, it is economically viable to extract about 288 MJ of electricity from the residues of one tonne of sugarcane, of which about 180 MJ are used in the plant itself. Thus a medium-size distillery processing 1 million tonnes of sugarcane per year could sell about 5 MW of surplus electricity. At current prices, it would earn US$ 18 million from sugar and ethanol sales, and about US$ 1 million from surplus electricity sales. With advanced boiler and turbine technology, the electricity yield could be increased to 648 MJ per tonne of sugarcane, but current electricity prices do not justify the necessary investment. (According to one report, the World Bank would only finance investments in bagasse power generation if the price were at least US$19/GJ or US$0.068/kWh.)
Bagasse burning is environmentally friendly compared to other fuels like oil and coal. Its ash content is only 2.5% (against 30-50% of coal), and it contains no sulfur. Since it burns at relatively low temperatures, it produces little nitrous oxides. Moreover, bagasse is being sold for use as a fuel (replacing heavy fuel oil) in various industries, including citrus juice concentrate, vegetable oil, ceramics, and tyre recycling. The state of São Paulo alone used 2 million tonnes, saving about US$ 35 million in fuel oil imports.
Researchers working with cellulosic ethanol are trying to make the extraction of ethanol from sugarcane bagasse and other plants viable on an industrial scale.
Bioenergy is renewable energy made available from materials derived from biological sources. In its most narrow sense it is a synonym to biofuel, which is fuel derived from biological sources. In its broader sense it includes biomass, the biological material used as a biofuel, as well as the social, economic, scientific and technical fields associated with using biological sources for energy. This is a common misconception, as bioenergy is the energy extracted from the biomass, as the biomass is the fuel and the bioenergy is the energy contained in the fuel.
Biomass is any organic material which has stored sunlight in the form of chemical energy. As a fuel it may include wood, wood waste, straw, manure, sugar cane, and many other byproducts from a variety of agricultural processes.
There is a slight tendency for the word bioenergy to be favoured in Europe compared with biofuel in North America.
Solid Biomass
Biomass is material derived from recently living organisms, which includes plants, animals and their byproducts. Manure, garden waste and crop residues are all sources of biomass. It is a renewable energy source based on the carbon cycle, unlike other natural resources such as petroleum, coal, and nuclear fuels.
Animal waste is a persistent and unavoidable pollutant produced primarily by the animals housed in industrial-sized farms.
There are also agricultural products being grown for biofuel production. These include corn, switchgrass, and soybeans, primarily in the United States; rapeseed, wheat and sugar beet primarily in Europe; sugar cane in Brazil; palm oil and miscanthus in Southeast Asia; sorghum and cassava in China; and jatropha in India. Hemp has also been proven to work as a biofuel. Biodegradable outputs from industry, agriculture, forestry and households can be used for biofuel production, using e.g. anaerobic digestion to produce biogas, gasification to produce syngas or by direct combustion. Examples of biodegradable wastes include straw, timber, manure, rice husks, sewage, and food waste. The use of biomass fuels can therefore contribute to waste management as well as fuel security and help to prevent or slow down climate change, although alone they are not a comprehensive solution to these problems.
Electricity generation from biomass
Electricity from sugarcane bagasse in Brazil
Sugar/Ethanol Plant located in Piracicaba, São Paulo State. This plant produces the electricity it needs from baggasse residuals from sugarcane left over by the milling process, and it sells the surplus electricity to the public grid.
Sucrose accounts for little more than 30% of the chemical energy stored in the mature plant; 35% is in the leaves and stem tips, which are left in the fields during harvest, and 35% are in the fibrous material (bagasse) left over from pressing.
The production process of sugar and ethanol in Brazil takes full advantage of the energy stored in sugarcane. Part of the baggasse is currently burned at the mill to provide heat for distillation and electricity to run the machinery. This allows ethanol plants to be energetically self-sufficient and even sell surplus electricity to utilities; current production is 600 MW for self-use and 100 MW for sale. This secondary activity is expected to boom now that utilities have been induced to pay "fair price "(about US$10/GJ or US$0.036/kWh) for 10 year contracts. This is approximately half of what the World Bank considers the reference price for investing in similar projects (see below). The energy is especially valuable to utilities because it is produced mainly in the dry season when hydroelectric dams are running low. Estimates of potential power generation from bagasse range from 1,000 to 9,000 MW, depending on technology. Higher estimates assume gasification of biomass, replacement of current low-pressure steam boilers and turbines by high-pressure ones, and use of harvest trash currently left behind in the fields. For comparison, Brazil's Angra I nuclear plant generates 657 MW.
Presently, it is economically viable to extract about 288 MJ of electricity from the residues of one tonne of sugarcane, of which about 180 MJ are used in the plant itself. Thus a medium-size distillery processing 1 million tonnes of sugarcane per year could sell about 5 MW of surplus electricity. At current prices, it would earn US$ 18 million from sugar and ethanol sales, and about US$ 1 million from surplus electricity sales. With advanced boiler and turbine technology, the electricity yield could be increased to 648 MJ per tonne of sugarcane, but current electricity prices do not justify the necessary investment. (According to one report, the World Bank would only finance investments in bagasse power generation if the price were at least US$19/GJ or US$0.068/kWh.)
Bagasse burning is environmentally friendly compared to other fuels like oil and coal. Its ash content is only 2.5% (against 30-50% of coal), and it contains no sulfur. Since it burns at relatively low temperatures, it produces little nitrous oxides. Moreover, bagasse is being sold for use as a fuel (replacing heavy fuel oil) in various industries, including citrus juice concentrate, vegetable oil, ceramics, and tyre recycling. The state of São Paulo alone used 2 million tonnes, saving about US$ 35 million in fuel oil imports.
Researchers working with cellulosic ethanol are trying to make the extraction of ethanol from sugarcane bagasse and other plants viable on an industrial scale.
Biochip
Biochip 
The development of biochips is a major thrust of the rapidly growing biotechnology industry, which encompasses a very diverse range of research efforts including genomics, proteomics, and pharmaceuticals, among other activities. Advances in these areas are giving scientists new methods for unraveling the complex biochemical processes occurring inside cells, with the larger goal of understanding and treating human diseases. At the same time, the semiconductor industry has been steadily perfecting the science of microminiaturization. The merging of these two fields in recent years has enabled biotechnologists to begin packing their traditionally bulky sensing tools into smaller and smaller spaces, onto so-called biochips. These chips are essentially miniaturized laboratories that can perform hundreds or thousands of simultaneous biochemical reactions. Biochips enable researchers to quickly screen large numbers of biological analytes for a variety of purposes, from disease diagnosis to detection of bioterrorism agents.
A biochip is a collection of miniaturized test sites (microarrays) arranged on a solid substrate that permits many tests to be performed at the same time in order to achieve higher output and speed. Biochips can also be used to perform techniques such as electrophoresis or PCR using microfluidics technology (Fan, 2009; Cady, 2009).
== History ==oxygen electrode, thereby relating oxygen levels to glucose concentration. This and similar biosensors became known as enzyme electrodes, and are still in use today.
In 1953, Watson and Crick announced their discovery of the now familiar double helix structure of DNA molecules and set the stage for genetics research that continues to the present day (Nelson, 2000). The development of sequencing techniques in 1977 by Gilbert (Maxam, 1977) and Sanger (Sanger, 1977) (working separately) enabled researchers to directly read the genetic codes that provide instructions for protein synthesis. This research showed how hybridization of complementary single oligonucleotide strands could be used as a basis for DNA sensing. Two additional developments enabled the technology used in modern DNA-based biosensors. First, in 1983 Kary Mullis invented the polymerase chain reaction (PCR) technique (Nelson, 2000), a method for amplifying DNA concentrations. This discovery made possible the detection of extremely small quantities of DNA in samples. Second, in 1986 Hood and coworkers devised a method to label DNA molecules with fluorescent tags instead of radiolabels (Smith, 1986), thus enabling hybridization experiments to be observed optically.
Biochar
Biochar
Biochar is charcoal created by pyrolysis of biomass. The resulting charcoal-like material can be used as a soil improver to create terra preta, and is a form of carbon capture and storage. Charcoal is a stable solid and rich in carbon content, and thus, can be used to lock carbon in the soil. Biochar is of increasing interest because of concerns about climate change caused by emissions of carbon dioxide (CO2) and other greenhouse gases (GHG).
Biochar is a way for carbon to be drawn from the atmosphere and is a solution to reducing the global impact of farming (and in reducing the impact from all agricultural waste). Since biochar can sequester carbon in the soil for hundreds to thousands of years, it has received considerable interest as a potential tool to slow global warming. The burning and natural decomposition of trees and agricultural matter contributes a large amount of CO2 released to the atmosphere. Biochar can store this carbon in the ground, potentially making a significant reduction in atmospheric GHG levels; at the same time its presence in the earth can improve water quality, increase soil fertility, raise agricultural productivity and reduce pressure on old growth forests. Current biochar projects are small scale and make no significant impact on the overall global carbon budget, although expansion of this technique has been advocated as a geoengineering approach. Further research is in progress, notably by the University of Edinburgh, which has a dedicated research unit.
Biochar is charcoal created by pyrolysis of biomass. The resulting charcoal-like material can be used as a soil improver to create terra preta, and is a form of carbon capture and storage. Charcoal is a stable solid and rich in carbon content, and thus, can be used to lock carbon in the soil. Biochar is of increasing interest because of concerns about climate change caused by emissions of carbon dioxide (CO2) and other greenhouse gases (GHG).
Biochar is a way for carbon to be drawn from the atmosphere and is a solution to reducing the global impact of farming (and in reducing the impact from all agricultural waste). Since biochar can sequester carbon in the soil for hundreds to thousands of years, it has received considerable interest as a potential tool to slow global warming. The burning and natural decomposition of trees and agricultural matter contributes a large amount of CO2 released to the atmosphere. Biochar can store this carbon in the ground, potentially making a significant reduction in atmospheric GHG levels; at the same time its presence in the earth can improve water quality, increase soil fertility, raise agricultural productivity and reduce pressure on old growth forests. Current biochar projects are small scale and make no significant impact on the overall global carbon budget, although expansion of this technique has been advocated as a geoengineering approach. Further research is in progress, notably by the University of Edinburgh, which has a dedicated research unit.
Uses of Biochar
Uses of Biochar
Carbon sink potential
Biochar can sequester carbon in the soil for hundreds to thousands of years. Modern biochar is being developed using pyrolysis to heat biomass in the absence of oxygen in kilns. Modern biochar production can be combined with biofuel production in a process that is exothermic (energy producing)—producing an output of 3-9 times more energy than invested, is carbon-negative—withdrawing CO2 from the atmosphere and rebuilds geological carbon sinks. This technique is advocated by prominent scientists such as James Hansen, an internationally-renowned climate scientist and head of NASA's Goddard Institute for Space Studies, and James Lovelock, creator of the Gaia hypothesis, for mitigation of global warming by greenhouse gas remediation.Biochar is a high-carbon, fine-grained residue which today is produced through modern pyrolysis processes. Pyrolysis is the direct thermal decomposition of biomass in the absence of oxygen to obtain an array of solid (biochar), liquid (bio-oil) and gas (syngas) products. The specific yield from the pyrolysis is dependent on process conditions, and can be optimized to produce either energy or biochar. Even when optimized to produce char rather than energy, the energy produced per unit energy input is higher than for corn ethanol.
Use as a carbon sink
Biochar can be used to sequester carbon on centurial or even millennial time scales. Plant matter absorbs CO2 from the atmosphere while growing. In the natural carbon cycle, plant matter decomposes rapidly after the plant dies, which emits CO2; the overall natural cycle is carbon neutral. Instead of allowing the plant matter to decompose, pyrolysis can be used to sequester the carbon in a much more stable form. Biochar thus removes circulating CO2 from the atmosphere and stores it in virtually permanent soil carbon pools, making it a carbon-negative process. In places like the Rocky Mountains, where beetles have been killing off vast swathes of pine trees, the utilization of pyrolysis to char the trees instead of letting them decompose into the atmosphere would offset substantial amounts of CO2 emissions. Although some organic matter is necessary for agricultural soil to maintain its productivity, much of the agricultural waste can be turned directly into biochar, bio-oil, and syngas. The use of pyrolysis also provides an opportunity for the processing of municipal waste into useful clean energy rather than increased problems with land space for storage.
Biochar is believed to have long mean residence times in the soil. While the methods by which biochar mineralizes (turns into CO2) are not completely known,evidence from soil samples in the Amazon shows large concentrations of black carbon (biochar) remaining after they were abandoned thousands of years ago. The amount of time the biochar will remain in the soil depends on the feedstock material, how charred the material is, the surface:volume ratio of the particles, and the conditions of the soil the biochar is placed in. Estimates for the residence time range from 100 to 10,000 yrs, with 5,000 being a common estimate. Lab experiments confirm a decrease in carbon mineralization with increasing temperature, so carefully controlled charring of plant matter can increase the soil residence time of the biochar C.
Under some circumstances, the addition of biochar to the soil has been found to accelerate the mineralization of the existing soil organic matter, but this would only reduce and not suppress the net benefit gained by sequestering carbon in the soil by this method. Furthermore, the suggested soil conditions for the integration of biochar are in heavily degraded tropical soils used for agriculture, not organic matter-rich boreal forest soils (as tested in the above reference).
Enhancing soil
In addition to its potential for carbon sequestration, biochar has numerous co-benefits when added to soil. It can prevent the leaching of nutrients out of the soil, increase the available nutrients for plant growth, increase water retention, and reduce the amount of fertilizer required. Additionally, it has been shown to decrease N2O (Nitrous oxide) and CH4 (methane) emissions from soil, thus further reducing GHG emissions. Biochar can be utilized in many applications as a replacement for or co-terminous strategy with other bioenergy production strategies. One of its most immediate uses is in switching from "slash-and-burn” to “slash-and-char” to prevent the rapid deforestation and subsequent degradation of soils.“Biochar sequestration does not require a fundamental scientific advance and the underlying production technology is robust and simple, making it appropriate for many regions of the world.” Johannes Lehmann, of Cornell University, estimates that pyrolysis will be cost feasible when the cost of a CO2 ton reaches $37, (as of the end of June 2008, CO2 is trading at $45/ton on the ECX) – so using pyrolysis for bioenergy production is feasible, even though it may be more expensive than fossil fuels at the moment.
Co-benefits for soil of pyrolysis
Biochar can be used as a soil amendment to increase plant growth yield, improve water quality, reduce soil emissions of GHGs, reduce leaching of nutrients, reduce soil acidity, and reduce irrigation and fertilizer requirements. These properties are very dependent on the properties of the biochar,and may depend on regional conditions including soil type, condition (depleted or healthy), temperature, and humidity. Modest additions of biochar to soil were found to reduce N2O emissions by up to 80% and completely suppress methane emissions.
Slash and charSwitching from slash-and-burn to slash-and-char techniques in Brazil can both decrease deforestation of the Amazon and increase the crop yield. Under the current method of slash-and-burn, only 3% of the carbon from the organic material is left in the soil.
Switching to slash-and-char can sequester up to 50% of the carbon in a highly stable form. Adding the biochar back into the soil rather than removing it all for energy production is necessary to avoid heavy increases in the cost and emissions from more required nitrogen fertilizers.Additionally, by improving the soil tilth, fertility, and productivity, the biochar enhanced soils can sustain agricultural production, whereas non-amended soils quickly become depleted of nutrients, and the fields are abandoned, leading to a continuous slash-and-burn cycle and the continued loss of tropical rainforest. Using pyrolysis to produce bio-energy also has the added benefit of not requiring infrastructure changes the way processing biomass for cellulosic ethanol does. Additionally, the biochar produced can be applied by the currently used tillage machinery or equipment used to apply fertilizer.
Energy production: bio-oil
Bio-oil can be used as a replacement for numerous applications where fuel oil is used, including fueling space heaters, furnaces, and boilers.Additionally, these biofuels can be used to fuel some combustion turbines and reciprocating engines, and as a source to create several chemicals. If bio-oil is used without modification, care must be taken to prevent emissions of black carbon and other particulates. Syngas and bio-oil can also be “upgraded” to transportation fuels like biodiesel and gasoline substitutes. If biochar is used for the production of energy rather than as a soil amendment, it can be directly substituted for any application that uses coal. pyrolysis also may be the most cost-effective way of producing electrical energy from biomaterial. Syngas can be burned directly, used as a fuel for gas engines and gas turbines, converted to clean diesel fuel through Fischer Tropsch or potentially used in the production of methanol and hydrogen.
Bio-oil has a much higher energy density than the raw biomass material.Mobile pyrolysis units can be used to lower the costs of transportation of the biomass itself if the biochar is returned to the soil and the syngas stream is used to power the process. Bio-oil contains organic acids which are corrosive to steel containers, has a high water vapor content which is detrimental to ignition, and, unless carefully cleaned, contains some biochar particles which can block injectors. The greatest potential for bio-oil seems to be its use in a bio-refinery, where compounds that are valuable chemicals, pesticides, pharmaceuticals or food additives are first extracted, and the remainder is either upgraded to fuel or reformed to syngas.
Carbon sink potential
Biochar can sequester carbon in the soil for hundreds to thousands of years. Modern biochar is being developed using pyrolysis to heat biomass in the absence of oxygen in kilns. Modern biochar production can be combined with biofuel production in a process that is exothermic (energy producing)—producing an output of 3-9 times more energy than invested, is carbon-negative—withdrawing CO2 from the atmosphere and rebuilds geological carbon sinks. This technique is advocated by prominent scientists such as James Hansen, an internationally-renowned climate scientist and head of NASA's Goddard Institute for Space Studies, and James Lovelock, creator of the Gaia hypothesis, for mitigation of global warming by greenhouse gas remediation.Biochar is a high-carbon, fine-grained residue which today is produced through modern pyrolysis processes. Pyrolysis is the direct thermal decomposition of biomass in the absence of oxygen to obtain an array of solid (biochar), liquid (bio-oil) and gas (syngas) products. The specific yield from the pyrolysis is dependent on process conditions, and can be optimized to produce either energy or biochar. Even when optimized to produce char rather than energy, the energy produced per unit energy input is higher than for corn ethanol.
Use as a carbon sink
Biochar can be used to sequester carbon on centurial or even millennial time scales. Plant matter absorbs CO2 from the atmosphere while growing. In the natural carbon cycle, plant matter decomposes rapidly after the plant dies, which emits CO2; the overall natural cycle is carbon neutral. Instead of allowing the plant matter to decompose, pyrolysis can be used to sequester the carbon in a much more stable form. Biochar thus removes circulating CO2 from the atmosphere and stores it in virtually permanent soil carbon pools, making it a carbon-negative process. In places like the Rocky Mountains, where beetles have been killing off vast swathes of pine trees, the utilization of pyrolysis to char the trees instead of letting them decompose into the atmosphere would offset substantial amounts of CO2 emissions. Although some organic matter is necessary for agricultural soil to maintain its productivity, much of the agricultural waste can be turned directly into biochar, bio-oil, and syngas. The use of pyrolysis also provides an opportunity for the processing of municipal waste into useful clean energy rather than increased problems with land space for storage.
Biochar is believed to have long mean residence times in the soil. While the methods by which biochar mineralizes (turns into CO2) are not completely known,evidence from soil samples in the Amazon shows large concentrations of black carbon (biochar) remaining after they were abandoned thousands of years ago. The amount of time the biochar will remain in the soil depends on the feedstock material, how charred the material is, the surface:volume ratio of the particles, and the conditions of the soil the biochar is placed in. Estimates for the residence time range from 100 to 10,000 yrs, with 5,000 being a common estimate. Lab experiments confirm a decrease in carbon mineralization with increasing temperature, so carefully controlled charring of plant matter can increase the soil residence time of the biochar C.
Under some circumstances, the addition of biochar to the soil has been found to accelerate the mineralization of the existing soil organic matter, but this would only reduce and not suppress the net benefit gained by sequestering carbon in the soil by this method. Furthermore, the suggested soil conditions for the integration of biochar are in heavily degraded tropical soils used for agriculture, not organic matter-rich boreal forest soils (as tested in the above reference).
Enhancing soil
In addition to its potential for carbon sequestration, biochar has numerous co-benefits when added to soil. It can prevent the leaching of nutrients out of the soil, increase the available nutrients for plant growth, increase water retention, and reduce the amount of fertilizer required. Additionally, it has been shown to decrease N2O (Nitrous oxide) and CH4 (methane) emissions from soil, thus further reducing GHG emissions. Biochar can be utilized in many applications as a replacement for or co-terminous strategy with other bioenergy production strategies. One of its most immediate uses is in switching from "slash-and-burn” to “slash-and-char” to prevent the rapid deforestation and subsequent degradation of soils.“Biochar sequestration does not require a fundamental scientific advance and the underlying production technology is robust and simple, making it appropriate for many regions of the world.” Johannes Lehmann, of Cornell University, estimates that pyrolysis will be cost feasible when the cost of a CO2 ton reaches $37, (as of the end of June 2008, CO2 is trading at $45/ton on the ECX) – so using pyrolysis for bioenergy production is feasible, even though it may be more expensive than fossil fuels at the moment.
Co-benefits for soil of pyrolysis
Biochar can be used as a soil amendment to increase plant growth yield, improve water quality, reduce soil emissions of GHGs, reduce leaching of nutrients, reduce soil acidity, and reduce irrigation and fertilizer requirements. These properties are very dependent on the properties of the biochar,and may depend on regional conditions including soil type, condition (depleted or healthy), temperature, and humidity. Modest additions of biochar to soil were found to reduce N2O emissions by up to 80% and completely suppress methane emissions.
Slash and charSwitching from slash-and-burn to slash-and-char techniques in Brazil can both decrease deforestation of the Amazon and increase the crop yield. Under the current method of slash-and-burn, only 3% of the carbon from the organic material is left in the soil.
Switching to slash-and-char can sequester up to 50% of the carbon in a highly stable form. Adding the biochar back into the soil rather than removing it all for energy production is necessary to avoid heavy increases in the cost and emissions from more required nitrogen fertilizers.Additionally, by improving the soil tilth, fertility, and productivity, the biochar enhanced soils can sustain agricultural production, whereas non-amended soils quickly become depleted of nutrients, and the fields are abandoned, leading to a continuous slash-and-burn cycle and the continued loss of tropical rainforest. Using pyrolysis to produce bio-energy also has the added benefit of not requiring infrastructure changes the way processing biomass for cellulosic ethanol does. Additionally, the biochar produced can be applied by the currently used tillage machinery or equipment used to apply fertilizer.
Energy production: bio-oil
Bio-oil can be used as a replacement for numerous applications where fuel oil is used, including fueling space heaters, furnaces, and boilers.Additionally, these biofuels can be used to fuel some combustion turbines and reciprocating engines, and as a source to create several chemicals. If bio-oil is used without modification, care must be taken to prevent emissions of black carbon and other particulates. Syngas and bio-oil can also be “upgraded” to transportation fuels like biodiesel and gasoline substitutes. If biochar is used for the production of energy rather than as a soil amendment, it can be directly substituted for any application that uses coal. pyrolysis also may be the most cost-effective way of producing electrical energy from biomaterial. Syngas can be burned directly, used as a fuel for gas engines and gas turbines, converted to clean diesel fuel through Fischer Tropsch or potentially used in the production of methanol and hydrogen.
Bio-oil has a much higher energy density than the raw biomass material.Mobile pyrolysis units can be used to lower the costs of transportation of the biomass itself if the biochar is returned to the soil and the syngas stream is used to power the process. Bio-oil contains organic acids which are corrosive to steel containers, has a high water vapor content which is detrimental to ignition, and, unless carefully cleaned, contains some biochar particles which can block injectors. The greatest potential for bio-oil seems to be its use in a bio-refinery, where compounds that are valuable chemicals, pesticides, pharmaceuticals or food additives are first extracted, and the remainder is either upgraded to fuel or reformed to syngas.
Production of biochar
Production of biochar
The yield of products from pyrolysis varies heavily with temperature. The lower the temperature, the more char is created per unit biomass. High temperature pyrolysis is also known as gasification, and produces primarily syngas from the biomass. The two main methods of pyrolysis are “fast” pyrolysis and “slow” pyrolysis. Fast pyrolysis yields 60% bio-oil, 20% biochar, and 20% syngas, and can be done in seconds, whereas slow pyrolysis can be optimized to produce substantially more char (~50%), but takes on the order of hours to complete. For typical inputs, the energy required to run a “fast” pyrolyzer is approximately 15% of the energy that it outputs.Modern pyrolysis plants can be run entirely off of the syngas created by the pyrolysis process and thus output 3-9 times the amount of energy required to run.Alternatively, microwave technology has recently been used to efficiently convert organic matter to biochar on an industrial scale, producing ~50% char.
The ancient method for producing biochar as a soil additive was the “pit” or “trench” method, which created terra preta, or dark soil. While this method is still a potential to produce biochar in rural areas, it does not allow the harvest of either the bio-oil or syngas, and releases a large amount of CO2, black carbon, and other GHGs (and potentially, toxins) into the air. Modern companies are producing commercial-scale systems to process agricultural waste, paper byproducts, and even municipal waste.
There are three primary methods for deploying a pyrolysis system. The first is a centralized system where all biomass in the region would be brought to a pyrolysis plant for processing. A second system would effectively mean a lower-tech pyrolysis kiln for each farmer or small group of farmers. A third system is a mobile system where a truck equipped with a pyrolyzer would be driven around to pyrolyze biomass. It would be powered using the syngas stream, return the biochar to the earth, and transport the bio-oil to a refinery or storage site. Whether a centralized system, a distributed system, or a mobile system is preferred is heavily dependent on the specific region. The cost of transportation of the liquid and solid byproducts, the amount of material to be processed in a region, and the ability to feed directly into the power grid are all factors to be considered when deciding on a specific implementation.
Unless crops are going to be dedicated to biochar production, the residue-to-product ratio (RPR) for the feedstock material is a useful gauge of the approximate amount of feedstock that can be obtained for pyrolysis after the primary product is harvested and the waste remains. The amount of crop residue available to be used for pyrolysis can be determined by using the RPR, and the collection factor (the percent of the residue not used for other things). For instance, Brazil harvests approximately 460Mt of sugar cane annually, with an RPR of 0.30, and a collection factor (CF) of 0.70 for the sugar cane tops, which are normally burned on the field. This translates into approximately 100Mt of residue which can be pyrolyzed to create energy and soil additives annually. Adding in the bagasse (sugar cane waste) (RPR=0.29 CF=1.0) which is currently burned inefficiently in boilers, raises the total to 230 Mt of pyrolysis feedstock just from sugar cane residues. Some plant residue, however, must remain on the soil to avoid heavily increased costs and emissions from nitrogen fertilizers.
The yield of products from pyrolysis varies heavily with temperature. The lower the temperature, the more char is created per unit biomass. High temperature pyrolysis is also known as gasification, and produces primarily syngas from the biomass. The two main methods of pyrolysis are “fast” pyrolysis and “slow” pyrolysis. Fast pyrolysis yields 60% bio-oil, 20% biochar, and 20% syngas, and can be done in seconds, whereas slow pyrolysis can be optimized to produce substantially more char (~50%), but takes on the order of hours to complete. For typical inputs, the energy required to run a “fast” pyrolyzer is approximately 15% of the energy that it outputs.Modern pyrolysis plants can be run entirely off of the syngas created by the pyrolysis process and thus output 3-9 times the amount of energy required to run.Alternatively, microwave technology has recently been used to efficiently convert organic matter to biochar on an industrial scale, producing ~50% char.
The ancient method for producing biochar as a soil additive was the “pit” or “trench” method, which created terra preta, or dark soil. While this method is still a potential to produce biochar in rural areas, it does not allow the harvest of either the bio-oil or syngas, and releases a large amount of CO2, black carbon, and other GHGs (and potentially, toxins) into the air. Modern companies are producing commercial-scale systems to process agricultural waste, paper byproducts, and even municipal waste.
There are three primary methods for deploying a pyrolysis system. The first is a centralized system where all biomass in the region would be brought to a pyrolysis plant for processing. A second system would effectively mean a lower-tech pyrolysis kiln for each farmer or small group of farmers. A third system is a mobile system where a truck equipped with a pyrolyzer would be driven around to pyrolyze biomass. It would be powered using the syngas stream, return the biochar to the earth, and transport the bio-oil to a refinery or storage site. Whether a centralized system, a distributed system, or a mobile system is preferred is heavily dependent on the specific region. The cost of transportation of the liquid and solid byproducts, the amount of material to be processed in a region, and the ability to feed directly into the power grid are all factors to be considered when deciding on a specific implementation.
Unless crops are going to be dedicated to biochar production, the residue-to-product ratio (RPR) for the feedstock material is a useful gauge of the approximate amount of feedstock that can be obtained for pyrolysis after the primary product is harvested and the waste remains. The amount of crop residue available to be used for pyrolysis can be determined by using the RPR, and the collection factor (the percent of the residue not used for other things). For instance, Brazil harvests approximately 460Mt of sugar cane annually, with an RPR of 0.30, and a collection factor (CF) of 0.70 for the sugar cane tops, which are normally burned on the field. This translates into approximately 100Mt of residue which can be pyrolyzed to create energy and soil additives annually. Adding in the bagasse (sugar cane waste) (RPR=0.29 CF=1.0) which is currently burned inefficiently in boilers, raises the total to 230 Mt of pyrolysis feedstock just from sugar cane residues. Some plant residue, however, must remain on the soil to avoid heavily increased costs and emissions from nitrogen fertilizers.
Tuesday, August 11, 2009
Asynchronous circuit
Asynchronous circuit
An asynchronous circuit is a circuit in which the parts are largely autonomous. They are not governed by a clock circuit or global clock signal, but instead need only wait for the signals that indicate completion of instructions and operations. These signals are specified by simple data transfer protocols. This digital logic design is contrasted with a synchronous circuit which operates according to clock timing signals.
Theoretical foundations
Petri Nets are an attractive and powerful model for reasoning about asynchronous circuits. However Petri nets have been criticized by Carl Hewitt for their lack of physical realism (see Petri net#Subsequent models of concurrency). Subsequent to Petri nets other models of concurrency have been developed that can model asynchronous circuits including the Actor model and process calculi.
The term asynchronous logic is used to describe a variety of design styles, which use different assumptions about circuit properties. These vary from the bundled delay model - which uses 'conventional' data processing elements with completion indicated by a locally generated delay model - to delay-insensitive design - where arbitrary delays through circuit elements can be accommodated. The latter style tends to yield circuits which are larger and slower than synchronous (or bundled data) implementations, but which are insensitive to layout and parametric variations and are thus "correct by design."
Benefits
Different classes of asynchronous circuitry offer different advantages. Below is a list of the advantages offered by Quasi Delay Insensitive Circuits, generally agreed to be the most "pure" form of asynchronous logic that retains computational universality. Less pure forms of asynchronous circuitry offer better performance at the cost of compromising one or more of these advantages:
* Robust handling of metastability of arbiters.* Early Completion of a circuit when it is known that the inputs which have not yet arrived are irrelevant.* Possibly lower power consumption because no transistor ever transitions unless it is performing useful computation (clock gating in synchronous designs is an imperfect approximation of this ideal). Also, clock drivers can be removed which can significantly reduce power consumption. However, when using certain encodings, asynchronous circuits may require more area, which can result in increased power consumption if the underlying process has poor leakage properties (for example, deep submicrometer processes used prior to the introduction of high-K dielectrics).* Freedom from the ever-worsening difficulties of distributing a high-fanout, timing-sensitive clock signal.* Better modularity and composability.* Far fewer assumptions about the manufacturing process are required (most assumptions are timing assumptions).* Circuit speed is adapted on the fly to changing temperature and voltage conditions rather than being locked at the speed mandated by worst-case assumptions.* Immunity to transistor-to-transistor variability in the manufacturing process, which is one of the most serious problems facing the semiconductor industry as dies shrink.* Less severe electromagnetic interference. Synchronous circuits create a great deal of EMI in the frequency band at (or very near) their clock frequency and its harmonics; asynchronous circuits generate EMI patterns which are much more evenly spread across the spectrum.* In asynchronous circuits, local signaling eliminates the need for global synchronization which exploits some potential advantages in comparison with synchronous ones. They have shown potential specifications in low power consumption, design reuse, improved noise immunity and electromagnetic compatibility. Asynchronous circuits are more tolerant to process variations and external voltage fluctuations.
Disadvantages
* Increased Complexity* More Difficult to Design* the performance analysis of asynchronous circuits is a complicated problem
Applications
Asynchronous CPU
Asynchronous CPUs are one of several ideas for radically changing CPU design.
Unlike a conventional processor, a clockless processor (asynchronous CPU) has no central clock to coordinate the progress of data through the pipeline. Instead, stages of the CPU are coordinated using logic devices called "pipeline controls" or "FIFO sequencers." Basically, the pipeline controller clocks the next stage of logic when the existing stage is complete. In this way, a central clock is unnecessary. It may actually be even easier to implement high performance devices in asynchronous, as opposed to clocked, logic:
* components can run at different speeds on an asynchronous CPU; all major components of a clocked CPU must remain synchronized with the central clock;* a traditional CPU cannot "go faster" than the expected worst-case performance of the slowest stage/instruction/component. When an asynchronous CPU completes an operation more quickly than anticipated, the next stage can immediately begin processing the results, rather than waiting for synchronization with a central clock. An operation might finish faster than normal because of attributes of the data being processed (e.g., multiplication can be very fast when multiplying by 0 or 1, even when running code produced by a naive compiler), or because of the presence of a higher voltage or bus speed setting, or a lower ambient temperature, than 'normal' or expected.
Asynchronous logic proponents believe these capabilities would have these benefits:
* lower power dissipation for a given performance level, and* highest possible execution speeds.
The biggest disadvantage of the clockless CPU is that most CPU design tools assume a clocked CPU (i.e., a synchronous circuit). Many tools "enforce synchronous design practices". Making a clockless CPU (designing an asynchronous circuit) involves modifying the design tools to handle clockless logic and doing extra testing to ensure the design avoids metastable problems. The group that designed the aforementioned AMULET, for example, developed a tool called LARD to cope with the complex design of AMULET3.
Despite the difficulty of doing so, numerous asynchronous CPUs have been built, including:
* the ORDVAC (?) and the (identical) ILLIAC I (1951), * the ILLIAC II (1962);* The Caltech Asynchronous Microprocessor, the world-first asynchronous microprocessor (1988);* the ARM-implementing AMULET (1993 and 2000);* the asynchronous implementation of MIPS R3000, dubbed MiniMIPS (1998);* the SEAforth multi-core processor (2008) from Charles H. Moore.
The ILLIAC II was the first completely asynchronous, speed independent processor design ever built; it was the most powerful computing machine known to man at the time.
DEC PDP-16 Register Transfer Modules (ca. 1973) allowed the experimenter to construct asynchronous, 16-bit processing elements. Delays for each module were fixed and based on the module's worst-case timing.
The Caltech Asynchronous Microprocessor (1988) was the first asynchronous microprocessor (1988). Caltech designed and manufactured the world's first fully Quasi Delay Insensitive processor. During demonstrations, the researchers amazed viewers by loading a simple program which ran in a tight loop, pulsing one of the output lines after each instruction. This output line was connected to an oscilloscope. When a cup of hot coffee was placed on the chip, the pulse rate (the effective "clock rate") naturally slowed down to adapt to the worsening performance of the heated transistors. When liquid nitrogen was poured on the chip, the instruction rate shot up with no additional intervention. Additionally, at lower temperatures, the voltage supplied to the chip could be safely increased, which also improved the instruction rate -- again, with no additional configuration.
An asynchronous circuit is a circuit in which the parts are largely autonomous. They are not governed by a clock circuit or global clock signal, but instead need only wait for the signals that indicate completion of instructions and operations. These signals are specified by simple data transfer protocols. This digital logic design is contrasted with a synchronous circuit which operates according to clock timing signals.
Theoretical foundations
Petri Nets are an attractive and powerful model for reasoning about asynchronous circuits. However Petri nets have been criticized by Carl Hewitt for their lack of physical realism (see Petri net#Subsequent models of concurrency). Subsequent to Petri nets other models of concurrency have been developed that can model asynchronous circuits including the Actor model and process calculi.
The term asynchronous logic is used to describe a variety of design styles, which use different assumptions about circuit properties. These vary from the bundled delay model - which uses 'conventional' data processing elements with completion indicated by a locally generated delay model - to delay-insensitive design - where arbitrary delays through circuit elements can be accommodated. The latter style tends to yield circuits which are larger and slower than synchronous (or bundled data) implementations, but which are insensitive to layout and parametric variations and are thus "correct by design."
Benefits
Different classes of asynchronous circuitry offer different advantages. Below is a list of the advantages offered by Quasi Delay Insensitive Circuits, generally agreed to be the most "pure" form of asynchronous logic that retains computational universality. Less pure forms of asynchronous circuitry offer better performance at the cost of compromising one or more of these advantages:
* Robust handling of metastability of arbiters.* Early Completion of a circuit when it is known that the inputs which have not yet arrived are irrelevant.* Possibly lower power consumption because no transistor ever transitions unless it is performing useful computation (clock gating in synchronous designs is an imperfect approximation of this ideal). Also, clock drivers can be removed which can significantly reduce power consumption. However, when using certain encodings, asynchronous circuits may require more area, which can result in increased power consumption if the underlying process has poor leakage properties (for example, deep submicrometer processes used prior to the introduction of high-K dielectrics).* Freedom from the ever-worsening difficulties of distributing a high-fanout, timing-sensitive clock signal.* Better modularity and composability.* Far fewer assumptions about the manufacturing process are required (most assumptions are timing assumptions).* Circuit speed is adapted on the fly to changing temperature and voltage conditions rather than being locked at the speed mandated by worst-case assumptions.* Immunity to transistor-to-transistor variability in the manufacturing process, which is one of the most serious problems facing the semiconductor industry as dies shrink.* Less severe electromagnetic interference. Synchronous circuits create a great deal of EMI in the frequency band at (or very near) their clock frequency and its harmonics; asynchronous circuits generate EMI patterns which are much more evenly spread across the spectrum.* In asynchronous circuits, local signaling eliminates the need for global synchronization which exploits some potential advantages in comparison with synchronous ones. They have shown potential specifications in low power consumption, design reuse, improved noise immunity and electromagnetic compatibility. Asynchronous circuits are more tolerant to process variations and external voltage fluctuations.
Disadvantages
* Increased Complexity* More Difficult to Design* the performance analysis of asynchronous circuits is a complicated problem
Applications
Asynchronous CPU
Asynchronous CPUs are one of several ideas for radically changing CPU design.
Unlike a conventional processor, a clockless processor (asynchronous CPU) has no central clock to coordinate the progress of data through the pipeline. Instead, stages of the CPU are coordinated using logic devices called "pipeline controls" or "FIFO sequencers." Basically, the pipeline controller clocks the next stage of logic when the existing stage is complete. In this way, a central clock is unnecessary. It may actually be even easier to implement high performance devices in asynchronous, as opposed to clocked, logic:
* components can run at different speeds on an asynchronous CPU; all major components of a clocked CPU must remain synchronized with the central clock;* a traditional CPU cannot "go faster" than the expected worst-case performance of the slowest stage/instruction/component. When an asynchronous CPU completes an operation more quickly than anticipated, the next stage can immediately begin processing the results, rather than waiting for synchronization with a central clock. An operation might finish faster than normal because of attributes of the data being processed (e.g., multiplication can be very fast when multiplying by 0 or 1, even when running code produced by a naive compiler), or because of the presence of a higher voltage or bus speed setting, or a lower ambient temperature, than 'normal' or expected.
Asynchronous logic proponents believe these capabilities would have these benefits:
* lower power dissipation for a given performance level, and* highest possible execution speeds.
The biggest disadvantage of the clockless CPU is that most CPU design tools assume a clocked CPU (i.e., a synchronous circuit). Many tools "enforce synchronous design practices". Making a clockless CPU (designing an asynchronous circuit) involves modifying the design tools to handle clockless logic and doing extra testing to ensure the design avoids metastable problems. The group that designed the aforementioned AMULET, for example, developed a tool called LARD to cope with the complex design of AMULET3.
Despite the difficulty of doing so, numerous asynchronous CPUs have been built, including:
* the ORDVAC (?) and the (identical) ILLIAC I (1951), * the ILLIAC II (1962);* The Caltech Asynchronous Microprocessor, the world-first asynchronous microprocessor (1988);* the ARM-implementing AMULET (1993 and 2000);* the asynchronous implementation of MIPS R3000, dubbed MiniMIPS (1998);* the SEAforth multi-core processor (2008) from Charles H. Moore.
The ILLIAC II was the first completely asynchronous, speed independent processor design ever built; it was the most powerful computing machine known to man at the time.
DEC PDP-16 Register Transfer Modules (ca. 1973) allowed the experimenter to construct asynchronous, 16-bit processing elements. Delays for each module were fixed and based on the module's worst-case timing.
The Caltech Asynchronous Microprocessor (1988) was the first asynchronous microprocessor (1988). Caltech designed and manufactured the world's first fully Quasi Delay Insensitive processor. During demonstrations, the researchers amazed viewers by loading a simple program which ran in a tight loop, pulsing one of the output lines after each instruction. This output line was connected to an oscilloscope. When a cup of hot coffee was placed on the chip, the pulse rate (the effective "clock rate") naturally slowed down to adapt to the worsening performance of the heated transistors. When liquid nitrogen was poured on the chip, the instruction rate shot up with no additional intervention. Additionally, at lower temperatures, the voltage supplied to the chip could be safely increased, which also improved the instruction rate -- again, with no additional configuration.
Applications and Layered architecture
Applications and Layered architecture
Communication network must support wide range of services. Normally people use networks to communicate, send e-mails, transfer of files and so on. Industry people use communication network for transfer of funds, update information about the product and so on. Hence, to provide support for current service and future services, a complete plan is required. This necessitates developing a complete flexibility in network architecture.communications functions are grouped into the following tasks• The transport across a network of data from a process in one machine to the process at another machine.• The routing and forwarding of packets across multiple hops in a network• The transfer of a frame of data from one physical interface to another.To reduce their design complexity, most networks are organized as a series of layers or levels, each one built upon its predecessor. The number of layers, the name of the each layer, the contents of each layer and the function of each layer differ from network to network.Interaction between the layers must be defined precisely. Interaction is done with definition of the service provided by each layer and to the layer above. Interface between layers through which a service is requested and through which results are conveyed. New services that build on existing services can be introduced even at the later stage. The layered approach accommodates incremental changes readily.We know , in all networks, the purpose of each layer is to offer certain services to the higher layers. The entities comprising the corresponding layers on different machines are called peer processes. Between each pair of adjacent layers there is an interface. The interface defines which primitive operations and services the lower layer offers to the upper one. The set of layers and protocols is called the network architecture.A protocol is a set of rules that governs how two or more communicating devices are to interact. HTTP protocol enables retrieval of web pages and TCP protocol enables the reliable transfer of streams of information between computers.HTTPLet us consider a client/server architecture, a server process in a computer waits for incoming requests by listening to a port. Port is an address that identifies which process is to receive a message that is delivered to a given machine. The server provide response to the requests. The server process always runs a process in the background called daemon. httpd refers to server daemon for HTTP. The documents are prepared using Hyper Text Markup Language (HTML) which consists of text, graphics and other media are interconnected by links that appear within the documents. The www is accessed through a browser program that displays the documents and allows the user to access other documents by clicking one of these links. Each link provides the browser with a uniform resource Locator (URL) that specifies the name of the machine where the document is located and the name of the file that contains the requested document. The HTTP ( Hyper Text Transfer Protocol ) specifies rules by which the client and server interacts so as to retrieve a document.In HTTP, we use two-way connection that transfer a stream of bytes in correct sequential order and without errors. The TCP protocol provides this type of communication service between two processes in two machines connected to a network. Each HTTP inserts its messages into a buffer and TCP transmits the contents of the buffer to the other TCP in blocks of information called segments. Each segment contains port number information in addition to the HTTP message information. The following figure shows how communication is carried between HTTP client and HTTP server.
AppleTalk Networking
AppleTalk
Implementing file transfer, printer sharing, and mail service among Apple systems using the Local Talk interface built into Apple hardware, these were the main tasks of AppleTalk developed by Apple Computer. AppleTalk ports to other network media such as Ethernet with the aod of LocalTalk to Ethernet bridges or by Ethernet add-in boards for Apple machines. In addition to many third-party applications, internetwork routing, transaction and data stream service, naming service, and comprehensive file and print sharing are some of the provisions of this multi-layered protocol. With the introduction of AppleTalk Phase 2 in 1989, the addressing capability of AppleTalk networks were extended and thereby provided compliance with the IEEE 802 standard. Some other additions present in AppleTalk Phase 2 were the range of available network layer addresses and the use of the IEEE 802.2 Logical Link Control (LLC) protocol at the Data Link Layer.
AppleTalk is a proprietary suite of protocols developed by Apple Inc for networking computers. It was included in the original Macintosh (1984) and is now deprecated by Apple in favor of TCP/IP networking. AppleTalk's Datagram Delivery Protocol corresponds closely to the Network layer of the Open Systems Interconnection (OSI) communication model.
The AppleTalk design rigorously followed the OSI model of protocol layering. Unlike most of the early LAN systems, AppleTalk was not built using the archetypal Xerox XNS system. The intended target was not Ethernet, and it did not have 48-bit addresses to route. Nevertheless, many portions of the AppleTalk system have direct analogs in XNS.
AppleTalk Address Resolution Protocol
AARP resolves AppleTalk addresses to physical layer, usually MAC, addresses. It is functionally equivalent to ARP.
AARP is a fairly simple system. When powered on, an AppleTalk machine broadcasts an AARP probe packet asking for a network address, intending to hear back from controllers such as routers. If no address is provided, one is picked at random from the "base subnet", 0. It then broadcasts another packet saying "I am selecting this address", and then waits to see if anyone else on the network complains. If another machine has that address, it will pick another address, and keep trying until it finds a free one. On a network with many machines it may take several tries before a free address is found, so for performance purposes the successful address is "written down" in NVRAM and used as the default address in the future. This means that in most real-world setups where machines are added a few at a time, only one or two tries are needed before the address effectively become constant.
AppleTalk is Apple's design of a simple, inexpensive and flexible network for connecting computers, peripheral devices, and servers. AppleTalk's flexibility allows it to be used to connect peripherals such as the LaserWriter, or act as a stand-alone local-area network for up to 32 nodes, or form portions of a larger network by using bridges and gateway devices.
What is AppleTalk? At a purely physical level, AppleTalk is a network with a bus topology that uses a trunk cable between connection modules. Interfacing with the network is handled by the Serial Communications Control chip found in every Mac. Any device (computer, peripheral, etc.) attaches to a connection box via a short cable (called a drop cable), as shown in figure 1. This type of network is known as a multidrop line or a multipoint link. AppleTalk is capable of supporting up to 32 nodes (devices) per network and can transmit data at a rate of 230,400 bits per second. Nodes can be separated by a maximum cable length of 1000 feet.
AppleTalk, as specified by Apple, is wired using relatively inexpensive shielded, twisted-pair cable and Apple's connection boxes. One box is required per device; in the case of the Mac, the box plugs into the serial printer port in the back of the Mac using an attached drop cable. A trunk cable segment from one node on the network plugs into one port on the connection box, and another cable segment leading to the next node in the network plugs into the other port on the box.
One of the advantages of AppleTalk relates to the design of these connection boxes. The boxes are designed so that the continuity of the trunk cable and the network is maintained even if a device is disconnected from the network by unplugging it from the connection box. (Unplugging the trunk from the connection box does disrupt the integrity of the network, however.) The physical layout of an AppleTalk network can therefore be designed by locating the connection boxes where desired without worrying if a device will be initially connected to each one of the boxes. Additional devices can be added to the network at any time simply by plugging them into the boxes.
There are alternatives to using Apple's connection boxes. Farallon Computing markets their PhoneNET system, which fully supports the AppleTalk protocols. In the case of PhoneNET, the physical transmission medium is ordinary telephone wire, allowing the user to use the in-house telephone wiring for his network. PhoneNET uses the two of the unused wires found in a normal telephone installation, supporting both a telephone and a Mac connected to the same telephone wall box. In addition, PhoneNET links are capable of supporting 3000-foot distances between nodes. Farallon has a series of devices (repeaters, Star Controller) for extending the network.
With the recent announcement of DuPont's system for AppleTalk, users can also use fiber optic connections for an AppleTalk network. A concentrator is also available for constructing star networks. Two advantages of the fiber optics system are its immunity to EMI-RFI interference and improved data security; nodes may be a maximum of 4900 feet apart.
AppleTalk Protocols and the OSI Model
The Physical Layer has the responsibility of bit encoding/decoding, synchronization, signal transmission/ reception and carrier sensing. As mentioned previously, the Serial Communications Control chip in the Mac takes care of the AppleTalk port, which happens to be the printer port on current Macs. As long as connection modules conform to the signal descriptions of the Physical Layer, any transmission medium can be used for the actual network.
The AppleTalk Link Access Protocol (ALAP) must be common to all systems on the network bus and handles the node-to-node delivery of data between devices connected to a single AppleTalk network. ALAP determines when the bus is free, encapsulates the data in frames, sends its data, and recognizes when data should be received. ALAP is also responsible for assigning node numbers to each station on a network. The ALAP software assigns a random node number when the Mac is booted and keeps that number as long as it does not conflict with a previously assigned node number (if it does conflict, ALAP tries again).
The Link Access Protocol uses a method called CSMA/CA, or carrier-sense multiple access with collision avoidance, for access control. Carrier sense means that a sending node first listens to the network to hear if any other node is using the bus and defers to the ongoing transmission. Collision avoidance means that the protocol attempts to minimize collisions between transmitted data packets. In AppleTalk CSMA/CA, all transmitters wait until the bus is idle for a minimum time plus a random amount of added time before transmitting (or retransmitting after a collision).
While the ALAP protocol provides delivery of data over a single AppleTalk network, the Datagram Delivery Protocol (DDP) extends this mechanism to include a group of interconnected AppleTalk networks, known as an internet. An internet can be formed, for example, by using a bridge between two, or more, AppleTalk networks.
AppleTalk's address header (a part of each data packet) is used for identification of a process on the network and consists of a socket number, node number, and network number. A socket is a communication endpoint within a node on the network. Sockets belong to processes or functions that are implemented within software in the node. One Mac may have several AppleTalk connections open at one time, so the node number is not enough to identify a network address. In addition, node numbers are unique only within a single physical network, so DDP requires that each network be assigned a network number. The Datagram Delivery Protocol takes care of assigning socket numbers, as well as node numbers and network numbers, to provide a unique identification for every process occurring on the AppleTalk network.
As we move on to the Transport Layer, several protocols exist to add different types of functionality to the underlying services. The Routing Table Maintenance Protocol (RTMP) allows bridges and internet routers to dynamically discover routes to the different AppleTalk networks in an internet. The routing tables pair network numbers with the local node number of the bridge through which the shortest path to that net exists.
The AppleTalk Transaction Protocol, or ATP, is part of the Transport Layer and is responsible for controlling the transactions (flow of data) between requestor and responder sockets. This transaction-oriented protocol can be contrasted to other types of transport layers which support a two-way link between clients that can act as though they had an error-free hardwired link between them.
The basic function of the Name Binding Protocol (NBP) is the translation of a character string name into the internet address of the corresponding client. A key feature of the network is that most objects are accessible by name rather than by address (better for the user). NBP also introduces the concept of a zone, which is an arbitrary subset of networks in an internet where each network is in one and only one zone. The concept of zones is provided to assist the establishment of departmental or other user-understandable grouping of the entities of the internet. AppleTalk names consist of three fields: the object name (e.g., Dave), the type name (e.g., printer), and the zone name (e.g., Bldg. 1).
The Echo Protocol (EP) is a simple protocol that allows any node to send data to any other node on an AppleTalk internet and receive an echoed copy of that data in return. The Echo Protocol is mainly meant for network maintenance functions.
The specifications for the AppleTalk Data Stream Protocol (ADSP) have not yet been published (Inside AppleTalk, current version dated July 14, 1986). ADSP is designed to provide byte-stream data transmission in a full duplex mode between any two sockets on an AppleTalk internet. The Zone Information Protocol (ZIP) is used to maintain an internet-wide mapping of networks to zone names. Most of ZIP's services are transparent to the normal (non-bridge) node; the majority of ZIP is implemented in the bridges of an internet. ZIP is used by the Name Binding Protocol to determine which networks belong to a given zone.
In the Session Layer, the AppleTalk Session Protocol (ASP) is a general protocol designed to interact with ATP to provide for establishing, maintaining and closing sessions. Central to ASP is the concept of a session; two network entities, one in a workstations and the other in a server, can set up an ASP session between themselves (identified by a unique sessions identifier). ASP is an asymetric protocol in that the workstation initiates the session connection and issues sequences of commands, to which the server responds; the server may not send commands to the workstation.
The specifications for the AppleTalk Filing Protocol (AFP) have not been generally publicized. However, AFP has been finalized with the introduction of the AppleShare file server software from Apple, which uses AFP. AFP is a presentation layer protocol designed to control access to remote file systems
Implementing file transfer, printer sharing, and mail service among Apple systems using the Local Talk interface built into Apple hardware, these were the main tasks of AppleTalk developed by Apple Computer. AppleTalk ports to other network media such as Ethernet with the aod of LocalTalk to Ethernet bridges or by Ethernet add-in boards for Apple machines. In addition to many third-party applications, internetwork routing, transaction and data stream service, naming service, and comprehensive file and print sharing are some of the provisions of this multi-layered protocol. With the introduction of AppleTalk Phase 2 in 1989, the addressing capability of AppleTalk networks were extended and thereby provided compliance with the IEEE 802 standard. Some other additions present in AppleTalk Phase 2 were the range of available network layer addresses and the use of the IEEE 802.2 Logical Link Control (LLC) protocol at the Data Link Layer.
AppleTalk is a proprietary suite of protocols developed by Apple Inc for networking computers. It was included in the original Macintosh (1984) and is now deprecated by Apple in favor of TCP/IP networking. AppleTalk's Datagram Delivery Protocol corresponds closely to the Network layer of the Open Systems Interconnection (OSI) communication model.
The AppleTalk design rigorously followed the OSI model of protocol layering. Unlike most of the early LAN systems, AppleTalk was not built using the archetypal Xerox XNS system. The intended target was not Ethernet, and it did not have 48-bit addresses to route. Nevertheless, many portions of the AppleTalk system have direct analogs in XNS.
One key differentiation for AppleTalk was it contained three protocols aimed at making the system completely self-configuring. The AppleTalk address resolution protocol (AARP) allowed AppleTalk hosts to automatically generate their own network addresses, and the Name Binding Protocol (NBP) was a dynamic Domain Name System (DNS) system, mapping network addresses to user-readable names. Although systems similar to AARP existed in other systems, Banyan VINES for instance, nothing like NBP has existed until recently.Both AARP and NBP had defined ways to allow "controller" devices to override the default mechanisms. The concept was to allow routers to provide the information or "hardwire" the system to known addresses and names. On larger networks where AARP could cause problems as new nodes searched for free addresses, the addition of a router could reduce "chattiness." Together AARP and NBP made AppleTalk an easy-to-use networking system. New machines were added to the network by plugging them and optionally giving them a name. The NBP lists were examined and displayed by a program known as the Chooser which would display a list of machines on the local network, divided into classes such as file-servers and printers.One problem for AppleTalk is it was intended to be part of a project known as Macintosh Office, which would consist of a host machine providing routing, printer sharing and file sharing. However this project was canceled in 1986. Despite this, the LaserWriter included built-in AppleTalk. Apple released a file and print server known as the AppleShare File and Print Servers.Today AppleTalk support is provided for backward compatibility in many products, but the default networking on the Mac is TCP/IP. Starting with Mac OS X v10.2, Bonjour (originally named Rendezvous) provides similar discovery and configuration services for TCP/IP-based networks. Bonjour is Apple's implementation of ZeroConf, which was written specifically to bring NBP's ease-of-use to the TCP/IP world.
AppleTalk Address Resolution Protocol
AARP resolves AppleTalk addresses to physical layer, usually MAC, addresses. It is functionally equivalent to ARP.
AARP is a fairly simple system. When powered on, an AppleTalk machine broadcasts an AARP probe packet asking for a network address, intending to hear back from controllers such as routers. If no address is provided, one is picked at random from the "base subnet", 0. It then broadcasts another packet saying "I am selecting this address", and then waits to see if anyone else on the network complains. If another machine has that address, it will pick another address, and keep trying until it finds a free one. On a network with many machines it may take several tries before a free address is found, so for performance purposes the successful address is "written down" in NVRAM and used as the default address in the future. This means that in most real-world setups where machines are added a few at a time, only one or two tries are needed before the address effectively become constant.
AppleTalk is Apple's design of a simple, inexpensive and flexible network for connecting computers, peripheral devices, and servers. AppleTalk's flexibility allows it to be used to connect peripherals such as the LaserWriter, or act as a stand-alone local-area network for up to 32 nodes, or form portions of a larger network by using bridges and gateway devices.
What is AppleTalk? At a purely physical level, AppleTalk is a network with a bus topology that uses a trunk cable between connection modules. Interfacing with the network is handled by the Serial Communications Control chip found in every Mac. Any device (computer, peripheral, etc.) attaches to a connection box via a short cable (called a drop cable), as shown in figure 1. This type of network is known as a multidrop line or a multipoint link. AppleTalk is capable of supporting up to 32 nodes (devices) per network and can transmit data at a rate of 230,400 bits per second. Nodes can be separated by a maximum cable length of 1000 feet.
AppleTalk, as specified by Apple, is wired using relatively inexpensive shielded, twisted-pair cable and Apple's connection boxes. One box is required per device; in the case of the Mac, the box plugs into the serial printer port in the back of the Mac using an attached drop cable. A trunk cable segment from one node on the network plugs into one port on the connection box, and another cable segment leading to the next node in the network plugs into the other port on the box.
One of the advantages of AppleTalk relates to the design of these connection boxes. The boxes are designed so that the continuity of the trunk cable and the network is maintained even if a device is disconnected from the network by unplugging it from the connection box. (Unplugging the trunk from the connection box does disrupt the integrity of the network, however.) The physical layout of an AppleTalk network can therefore be designed by locating the connection boxes where desired without worrying if a device will be initially connected to each one of the boxes. Additional devices can be added to the network at any time simply by plugging them into the boxes.
There are alternatives to using Apple's connection boxes. Farallon Computing markets their PhoneNET system, which fully supports the AppleTalk protocols. In the case of PhoneNET, the physical transmission medium is ordinary telephone wire, allowing the user to use the in-house telephone wiring for his network. PhoneNET uses the two of the unused wires found in a normal telephone installation, supporting both a telephone and a Mac connected to the same telephone wall box. In addition, PhoneNET links are capable of supporting 3000-foot distances between nodes. Farallon has a series of devices (repeaters, Star Controller) for extending the network.
With the recent announcement of DuPont's system for AppleTalk, users can also use fiber optic connections for an AppleTalk network. A concentrator is also available for constructing star networks. Two advantages of the fiber optics system are its immunity to EMI-RFI interference and improved data security; nodes may be a maximum of 4900 feet apart.
AppleTalk Protocols and the OSI Model
The Physical Layer has the responsibility of bit encoding/decoding, synchronization, signal transmission/ reception and carrier sensing. As mentioned previously, the Serial Communications Control chip in the Mac takes care of the AppleTalk port, which happens to be the printer port on current Macs. As long as connection modules conform to the signal descriptions of the Physical Layer, any transmission medium can be used for the actual network.
The AppleTalk Link Access Protocol (ALAP) must be common to all systems on the network bus and handles the node-to-node delivery of data between devices connected to a single AppleTalk network. ALAP determines when the bus is free, encapsulates the data in frames, sends its data, and recognizes when data should be received. ALAP is also responsible for assigning node numbers to each station on a network. The ALAP software assigns a random node number when the Mac is booted and keeps that number as long as it does not conflict with a previously assigned node number (if it does conflict, ALAP tries again).
The Link Access Protocol uses a method called CSMA/CA, or carrier-sense multiple access with collision avoidance, for access control. Carrier sense means that a sending node first listens to the network to hear if any other node is using the bus and defers to the ongoing transmission. Collision avoidance means that the protocol attempts to minimize collisions between transmitted data packets. In AppleTalk CSMA/CA, all transmitters wait until the bus is idle for a minimum time plus a random amount of added time before transmitting (or retransmitting after a collision).
While the ALAP protocol provides delivery of data over a single AppleTalk network, the Datagram Delivery Protocol (DDP) extends this mechanism to include a group of interconnected AppleTalk networks, known as an internet. An internet can be formed, for example, by using a bridge between two, or more, AppleTalk networks.
AppleTalk's address header (a part of each data packet) is used for identification of a process on the network and consists of a socket number, node number, and network number. A socket is a communication endpoint within a node on the network. Sockets belong to processes or functions that are implemented within software in the node. One Mac may have several AppleTalk connections open at one time, so the node number is not enough to identify a network address. In addition, node numbers are unique only within a single physical network, so DDP requires that each network be assigned a network number. The Datagram Delivery Protocol takes care of assigning socket numbers, as well as node numbers and network numbers, to provide a unique identification for every process occurring on the AppleTalk network.
As we move on to the Transport Layer, several protocols exist to add different types of functionality to the underlying services. The Routing Table Maintenance Protocol (RTMP) allows bridges and internet routers to dynamically discover routes to the different AppleTalk networks in an internet. The routing tables pair network numbers with the local node number of the bridge through which the shortest path to that net exists.
The AppleTalk Transaction Protocol, or ATP, is part of the Transport Layer and is responsible for controlling the transactions (flow of data) between requestor and responder sockets. This transaction-oriented protocol can be contrasted to other types of transport layers which support a two-way link between clients that can act as though they had an error-free hardwired link between them.
The basic function of the Name Binding Protocol (NBP) is the translation of a character string name into the internet address of the corresponding client. A key feature of the network is that most objects are accessible by name rather than by address (better for the user). NBP also introduces the concept of a zone, which is an arbitrary subset of networks in an internet where each network is in one and only one zone. The concept of zones is provided to assist the establishment of departmental or other user-understandable grouping of the entities of the internet. AppleTalk names consist of three fields: the object name (e.g., Dave), the type name (e.g., printer), and the zone name (e.g., Bldg. 1).
The Echo Protocol (EP) is a simple protocol that allows any node to send data to any other node on an AppleTalk internet and receive an echoed copy of that data in return. The Echo Protocol is mainly meant for network maintenance functions.
The specifications for the AppleTalk Data Stream Protocol (ADSP) have not yet been published (Inside AppleTalk, current version dated July 14, 1986). ADSP is designed to provide byte-stream data transmission in a full duplex mode between any two sockets on an AppleTalk internet. The Zone Information Protocol (ZIP) is used to maintain an internet-wide mapping of networks to zone names. Most of ZIP's services are transparent to the normal (non-bridge) node; the majority of ZIP is implemented in the bridges of an internet. ZIP is used by the Name Binding Protocol to determine which networks belong to a given zone.
In the Session Layer, the AppleTalk Session Protocol (ASP) is a general protocol designed to interact with ATP to provide for establishing, maintaining and closing sessions. Central to ASP is the concept of a session; two network entities, one in a workstations and the other in a server, can set up an ASP session between themselves (identified by a unique sessions identifier). ASP is an asymetric protocol in that the workstation initiates the session connection and issues sequences of commands, to which the server responds; the server may not send commands to the workstation.
The specifications for the AppleTalk Filing Protocol (AFP) have not been generally publicized. However, AFP has been finalized with the introduction of the AppleShare file server software from Apple, which uses AFP. AFP is a presentation layer protocol designed to control access to remote file systems
Amoeba Organization
Amoeba Organization
Introducing the concept of AMOEBA ORGANIZATION based on adaptability, which is the key to business success of modern days; but many organizations are too rigidly organized to adapt to constant change & seize new opportunities. Modern day organizations are lengthening their life span by reshaping internal systems for flexibility, modernizing their cultures & monitoring the ever-changing environments in which they operate.
Introducing the concept of AMOEBA ORGANIZATION based on adaptability, which is the key to business success of modern days; but many organizations are too rigidly organized to adapt to constant change & seize new opportunities. Modern day organizations are lengthening their life span by reshaping internal systems for flexibility, modernizing their cultures & monitoring the ever-changing environments in which they operate.
Advantages of Biomass Energy
Advantages of Biomass Energy
The last five years has seen a revolution in how governments, people and industry view energy. The advantages of biomass energy have come to the forefront in this discussion. Advantages of Biomass EnergyThe most common practical expression of biomass energy is in the form of biofuels. Biodiesal and bioethanol are already being used to supplement gasoline products in an effort to cut emissions and wean America off oil products.
Biofuels are essentially nontoxic and biodegrade readily. Every gallon of biofuels used reduces the hazard of toxic petroleum product spills from oil tankers and pipeline leaks (average of 12 million gallons per year, more than what spilled from the Exxon Valdez, according to the U.S. Department of Transportation). In addition, using biofuels reduces the risk of groundwater contamination from underground gasoline storage tanks (more than 46 million gallons per year from 16,000 small oil spills, according to the General Accounting Office), and runoff of vehicle engine oil and fuel.The U.S. transportation sector is responsible for one-third of our country's carbon dioxide (CO2) emissions, the principal greenhouse gas contributing to global warming. Combustion of biofuels also releases CO2, but because biofuels are made from plants that just recently captured that CO2 from the atmosphere-rather than billions of years ago-that release is largely balanced by CO2 uptake for the plants' growth. The CO2 released when biomass is converted into biofuels and burned in truck or automobile engines is recaptured when new biomass is grown to produce more biofuels. Depending upon how much fossil energy is used to grow and process the biomass feedstock, this results in substantially reduced net greenhouse gas emissions. Modern, high-yield corn production is relatively energy intense, but the net greenhouse gas emission reduction from making ethanol from corn grain is still about 20%. Making biodiesel from soybeans reduces net emissions nearly 80%. Producing ethanol from cellulosic material also involves generating electricity by combusting the non-fermentable lignin. The combination of reducing both gasoline use and fossil electrical production can mean a greater than 100% net greenhouse gas emission reduction.Biomass generated electricity is another active area of research and production. Biomass electricity is typically generated through boiler/steam turbine plants, but with three key differences: the fuel is renewable, there is less than 0.1% sulfur (an acid rain ingredient) in biomass fuels, and less air pollutants are produced. More specific environmental benefits for biomass power are:
• Reduced Sulfur Dioxide Emissions - Most forms of biomass contain very small amounts of sulfur, therefore a biomass power plant emits very little sulfur dioxide (SO2), an acid rain precursor. Coal, however, usually contains up to 5% sulfur. Biomass mixed with coal can significantly reduce the power plant's SO2 emissions compared to a coal-only operation.• Reduced Nitrogen Oxide Emissions - Recent biomass tests at several coal-fired power plants in the U.S. have demonstrated that NOx emissions can be reduced relative to coal-only operations. By carefully adjusting the combustion process, NOx reductions at twice the rate of biomass heat input have been documented.• Reduced Carbon Emissions - Plants absorb CO2 during their growth cycle when managed in a sustainable cycle, like raising energy crops or replanting harvested areas. Biomass Power generation can be viewed as a way to recycle carbon. Thus, Biomass Power generation can be considered a carbon-neutral power generation option.• Reducing Other Emissions - Landfills produce methane (CH4) from decomposing biomass materials. Decomposing animal manure, whether it is land-applied or left uncovered in a lagoon also generates methane. Methane, which is the main component of natural gas, is normally discharged directly into the air, but it can be captured and used as a fuel to generate electricity and heat.• Reduced Odors - Using animal manure and landfill gas for energy production can reduce odors associated with conventional disposal or land applications.Biomass energy is not the perfect solution to our current energy and environmental concerns. The advantages of biomass energy, however, far outweigh those of fossil fuels.
The last five years has seen a revolution in how governments, people and industry view energy. The advantages of biomass energy have come to the forefront in this discussion. Advantages of Biomass EnergyThe most common practical expression of biomass energy is in the form of biofuels. Biodiesal and bioethanol are already being used to supplement gasoline products in an effort to cut emissions and wean America off oil products.
Biofuels are essentially nontoxic and biodegrade readily. Every gallon of biofuels used reduces the hazard of toxic petroleum product spills from oil tankers and pipeline leaks (average of 12 million gallons per year, more than what spilled from the Exxon Valdez, according to the U.S. Department of Transportation). In addition, using biofuels reduces the risk of groundwater contamination from underground gasoline storage tanks (more than 46 million gallons per year from 16,000 small oil spills, according to the General Accounting Office), and runoff of vehicle engine oil and fuel.The U.S. transportation sector is responsible for one-third of our country's carbon dioxide (CO2) emissions, the principal greenhouse gas contributing to global warming. Combustion of biofuels also releases CO2, but because biofuels are made from plants that just recently captured that CO2 from the atmosphere-rather than billions of years ago-that release is largely balanced by CO2 uptake for the plants' growth. The CO2 released when biomass is converted into biofuels and burned in truck or automobile engines is recaptured when new biomass is grown to produce more biofuels. Depending upon how much fossil energy is used to grow and process the biomass feedstock, this results in substantially reduced net greenhouse gas emissions. Modern, high-yield corn production is relatively energy intense, but the net greenhouse gas emission reduction from making ethanol from corn grain is still about 20%. Making biodiesel from soybeans reduces net emissions nearly 80%. Producing ethanol from cellulosic material also involves generating electricity by combusting the non-fermentable lignin. The combination of reducing both gasoline use and fossil electrical production can mean a greater than 100% net greenhouse gas emission reduction.Biomass generated electricity is another active area of research and production. Biomass electricity is typically generated through boiler/steam turbine plants, but with three key differences: the fuel is renewable, there is less than 0.1% sulfur (an acid rain ingredient) in biomass fuels, and less air pollutants are produced. More specific environmental benefits for biomass power are:
• Reduced Sulfur Dioxide Emissions - Most forms of biomass contain very small amounts of sulfur, therefore a biomass power plant emits very little sulfur dioxide (SO2), an acid rain precursor. Coal, however, usually contains up to 5% sulfur. Biomass mixed with coal can significantly reduce the power plant's SO2 emissions compared to a coal-only operation.• Reduced Nitrogen Oxide Emissions - Recent biomass tests at several coal-fired power plants in the U.S. have demonstrated that NOx emissions can be reduced relative to coal-only operations. By carefully adjusting the combustion process, NOx reductions at twice the rate of biomass heat input have been documented.• Reduced Carbon Emissions - Plants absorb CO2 during their growth cycle when managed in a sustainable cycle, like raising energy crops or replanting harvested areas. Biomass Power generation can be viewed as a way to recycle carbon. Thus, Biomass Power generation can be considered a carbon-neutral power generation option.• Reducing Other Emissions - Landfills produce methane (CH4) from decomposing biomass materials. Decomposing animal manure, whether it is land-applied or left uncovered in a lagoon also generates methane. Methane, which is the main component of natural gas, is normally discharged directly into the air, but it can be captured and used as a fuel to generate electricity and heat.• Reduced Odors - Using animal manure and landfill gas for energy production can reduce odors associated with conventional disposal or land applications.Biomass energy is not the perfect solution to our current energy and environmental concerns. The advantages of biomass energy, however, far outweigh those of fossil fuels.
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