No edit summary
Tag: n
(42 intermediate revisions by 12 users not shown)
Line 3: Line 3:
{{content from|Original:Biogas and liquid biofuels|Practical Action}}
{{content from|Original:Biogas and liquid biofuels|Practical Action}}


'''Biofuel''' is a type of [[fuel]] which is made using animal or plant-based resources which are regenerated quickly. Biofuels are hence different from [[fossil fuel]]s as although fossil fuels too are created trough [[anaerobic decomposition]] of buried dead organisms, this process takes a very long time (exceeding millions of years). This means that -unlike fossil fuels- biofuels are a form of closed-end [[WikiPedia:recycling|recycling]], whereby the waste product goes directly into production of the fuel. Like fossil fuels, biofuels are a form of indirect [[solar energy]].
'''Biofuel''' is a term used to describe [[fuel]] sources that are derived from easily regeneratable [[Biomass|animal or plant-based resources]]. Biofuels are categorically different from fossil fuels, as biofuel production is not based on the anaerobic decomposition of buried organic matter. Furthermore, fossil fuel deposits take millions of year to form and are a naturally occurring phenomenon while resources for biofuel production are usually considered renewable and are typically representative of the bi-product from some other production process. Biofuels are thus a form of closed-loop recycling [[WikiPedia:recycling|recycling]], as the waste product from some production process is re-appropriated in to fuel for the process itself. It should be noted that although biofuels vary greatly in nature from fossil fuels, they are both a form of indirect [[solar energy]]; the initial energetic input stored in these fuels originated from the sun and was captured via terrestrial primary production processes, or photosynthesis.
 
Biofuels can be divided in to two categories of First-generation and Second-generation:
 
{| class="wikitable"
|-
! First Generation 
! Second Generation
|-
| rowspan="3" | Describes biofuels that are derived from the edible parts of plants. A consideration associated with this form of biofuel is that large-scale production involves the mass cultivation of crops (such as maize) that could be otherwise be inputted into the global food system. Valuable resources such as arable land are thus prioritized for fuel production, rather than food production.
| Describes biofuels that are derived from non-edible parts of plants, such as woody stems, branches, etc.<ref>also called cellulosic alcohol</ref> or from fruits that are not a part of the human diet. A benefit associated with second generation biofuels is that, unlike first generation processes, production is not inversely related to global food system production. Second-generation biofuel can be further divided in 2+ generation-biofuels and 2++ generation-biofuels
|-
| '''2+ generation-biofuel''' production involves no use of arable land at all for energy production (i.e. [[algae fuel]])
|-
| '''2++ generation-biofuel''' production involves no use of arable land at all for energy production and no air pollution (this still occurs with the other biofuels, although there are no carbon emissions). (i.e. biohydrogen)
|}
 


==Background==
==Background==
[[Biomass]] residues can be used as is (solid biomass) or converted into various non-solid fuel forms. These fuels are referred to as [[biogas]] and [[liquid biofuels]]. The aim of this conversion process is to improve the quality, specific energy content, transportability, etc., of the raw biomass source or to capture gases which are naturally produced as biomass is micro biologically degraded or when biomass is partially combusted. Biogas is a well-established fuel for cooking and lighting in a number of countries, whilst a major motivating factor in the development of liquid biofuels has been the drive to replace petroleum fuels. In this fact sheet we will be looking at some of these fuels, their applications and the conversion technologies used to derive them.  
Residual [[biomass]] can be re-appropriated without any primary treatment processes (i.e. the use of solid biomass) or be converted into various non-solid fuel forms; these forms are referred to as [[biogas]] and [[liquid biofuel]]. The purpose of such refinement processes is to improve the quality, specific energy content, transportability, etc., of the raw biomass source. It also allows for the capture of gases, which would otherwise be released in to the atmosphere, during natural biomass degradation processes. An example of this is the release of methane from anaerobic digestion in biomass waste or stockpiles. <ref> Methane and nitrous oxide emissions from biomass waste stockpiles. BTG biomass technology group BV, 2002. </ref> These two forms of biofuel differ in there uses and applications; for example primary uses of biogas include cooking and lighting in a number of countries. On the other hand, development in liquid biofuel production has been driven by an ever-increasing societal need to displace fossil fuels as the default fuel source.
Within the context of acknowledged and growing anthropogenic impact on the global energy system, there has been notable movement towards cultivation of energy crops specifically for the production of biomass-derived fuel. These developments are taking place globally, across Europe, the United States as well as in several developing countries; as the human population continues to accelerate towards both complete extraction of fossil fuels, as well as catastrophic atmospheric CO2  levels, the need for integrated energy supply options has become increasingly overt. This need for supplementary and renewable fuel sources has thus catalyzed development of biofuel technology and will furthermore be the basis for which biomass re-appropriation will reach its full potential as an energy source.
In the following sections, a number of liquid biofuel forms will be outlined as well as their applications, and the conversion technologies used to derive them.


In Europe and the United States, as well as in several developing countries, there is a move toward cultivating energy crops specifically for the production of biomass as a fuel. The
==Environmental Considerations==
potential for energy production from biomass throughout the world is enormous and as fossil-based fuels become scarcer and more expensive, as carbon emission levels are becoming of greater concern and as people realise the benefits of developing integrated energy supply options, then biomass could begin to realise its full potential as an energy source.
There are two primary points of environmental concern, in relation to biomass-based energy derivation. The first point of concern is the potential for poor land management practices that are so often associated with any type fuel production. Examples of potential degrading production processes include large-scale implementation of mono-crops and the use of various chemical compounds to stimulate growth.  Considerations specific to biofuel crop harvesting include the removal of plant residual material that would otherwise be broken down and increase the organic matter contentions and can furthermore contribute to greenhouse gas emissions through losses of soil carbon. <ref> The State of Food and Agriculture. United Nations, 2008</ref>


==Biomass energy and the environment==
However, land degradation and deforestation that could potentially be fostered by production of biofuels can be circumvented via cohesive and regulated land management policy. Furthermore, integration of non-conventional farming methodology, such as [[Permaculture|companion planting]], [[Integrated pest management|IPM]] and conservation tillage into biofuel production policy could further reduce the potential for negative environmental impact associated with modern large-scale agricultural practices.  
There are two areas of environmental concern when considering using biomass as a form of energy. Firstly, there is the issue of land degradation and deforestation. This concern can be addressed by proper management of sustainable energy crops. Although much of the biomass requirement for energy production can be met through utilising residues from the
food industry, from agriculture or from commercial activity, careful planning of energy cropping is required to prevent undue stress on the environment.


The large growth in the use of biofuels has promoted large scale mono-crop feedstock production and associated problems.
The second point of concern relates to the inversal nature of first generation fuel production and food production.  This relationship was noted in the pervious sections. It arguable that such prioritization is not necessary, as much of the biomass requirement for energy production can be met through the re-appropriation of production bi-products (waste) or food industry residual material; you will remember that this form of biofuel is referred to as second generation. Policy infrastructure should thus be created with this consideration in mind, and limit the degree to which arable land and other production inputs can be employed for first generation biofuel production. Benefits to this limitation are two-fold, as it prevents undue stress on the environment related to biofuel production and restricts the degree to which this production can be prioritized over food production. For a more in depth outline of appropriate policy infrastructure, see <ref> Negussie,  A.,  Verbist,  B.J.P.  &  Muys,  B.  (2014). Invasiveness  prospects  of  Biofuels:  avoid invasiveness threat of novel tropical biofuel crops. KLIMOS-Policy Brief 7, KLIMOS, Leuven. </ref>.  


Localised decentralised biofuel production from feedstock grown using sustainable agricultural practices been shown to offer part of a sustainable energy portfolio.   
The use of [http://www.appropedia.org/wiki/File:Oil_crops.png crops that are native to the region] can also provide part of the answer. In addition to this, the exact place (and the current use of the location -ie food production, CO<sub>2</sub> already locked in the soil, ...) where the crops are planted also matters. According to Wouter Achten of KU Leuven, biofuel-crops are best planted in CO<sub>2</sub>-poor soils and which are currently not used for agriculture. The first is for obvious reasons: by requiring the farmer to fertilise the soil with CO<sub>2</sub> he locks away part of the CO<sub>2</sub> in the atmosphere. The downside however is that extra fertilisation (and thus an increased cost) is required. The second is for less obvious reasons: if the land is used for agriculture, the crops that were planted need to be relocated. This could mean that there is an extra CO<sub>2</sub>-cost in transport (crops need to be transported further). This is known as [[Indirect LandUse Change|ILUC]].
 
Localised decentralised biofuel production from feedstock grown using sustainable agricultural practices been shown to offer part of a sustainable energy portfolio. A good example is for example [[rapeseed]]. This crop creates both biofuel (oil) as animal feed (the rest of the plant).   


With the recent global call to reduce carbon dioxide emissions, there is a strong case for promoting the use of sustainable biomass-to-energy technologies worldwide. Using modern technology, enormous reductions can be made in carbon dioxide emissions, particularly if liquid biofuels are used to replace their fossil-based equivalents. In fact, if biomass energy production is done on a sustainable basis, there is little net carbon dioxide addition to the environment.
With the recent global call to reduce carbon dioxide emissions, there is a strong case for promoting the use of sustainable biomass-to-energy technologies worldwide. Using modern technology, enormous reductions can be made in carbon dioxide emissions, particularly if liquid biofuels are used to replace their fossil-based equivalents. In fact, if biomass energy production is done on a sustainable basis, there is little net carbon dioxide addition to the environment.
Line 23: Line 41:
There are other environmental concerns related to each fuel that need to be kept in mind, such as toxic emissions and production of tars and soots.<ref>Anderson, T., Doig, A., Rees, D. and Khennas, S., Rural Energy Services: A handbook for sustainable energy development. ITDG Publishing, 1999.</ref><ref>Ravindranath, N. H. and Hall, D. O., Biomass, Energy and the Environment: A Developing Country Perspective from India. Oxford University Press, 1995.</ref><ref>Karekezi, S. and Ranja, T., Renewable Energy Technologies in Africa. AFREPEN, 1997.</ref><ref>Kristoferson L. A., and Bokalders V., Renewable Energy Technologies - their application in developing countries. ITDG Publishing, 1991.</ref><ref>Johansen, T.B. et al, Renewable Energy Sources for Fuels and Electricity. Island Press, Washington D.C., 1993.</ref>
There are other environmental concerns related to each fuel that need to be kept in mind, such as toxic emissions and production of tars and soots.<ref>Anderson, T., Doig, A., Rees, D. and Khennas, S., Rural Energy Services: A handbook for sustainable energy development. ITDG Publishing, 1999.</ref><ref>Ravindranath, N. H. and Hall, D. O., Biomass, Energy and the Environment: A Developing Country Perspective from India. Oxford University Press, 1995.</ref><ref>Karekezi, S. and Ranja, T., Renewable Energy Technologies in Africa. AFREPEN, 1997.</ref><ref>Kristoferson L. A., and Bokalders V., Renewable Energy Technologies - their application in developing countries. ITDG Publishing, 1991.</ref><ref>Johansen, T.B. et al, Renewable Energy Sources for Fuels and Electricity. Island Press, Washington D.C., 1993.</ref>


==Pollution==
==Advantages and disadvantages==
[[WikiPedia:Pollution|Pollution]] is any byproduct that cannot be fed back into the closed-end system. For biofuels, this includes particulates and unburnt hydrocarbons (smoke), oxides of nitrogen, carbon monoxide, and a few others. These are typically much lower level than when fossil fuel is combusted, but they remain a problem.
Biofuels are not made from petroleum; not purchasing petroleum products allows you to avoid supporting business practices such as oil drilling that are harmful to the environment and human rights.  


What is pollution for one [[technology]] may be the biofuel in another. For example, if wood is heated anaerobically (with limited oxygen), it produces carbon monoxide, which is normally considered a pollutant, but if collected, can be burnt as a biofuel.<ref>[http://www.ecoreality.org/wiki/Biofuel Biofuel]</ref>
[[WikiPedia:Pollution|Pollution]] is any byproduct that cannot be fed back into the closed-end system. For biofuels (except for biohydrogen), this includes particulates and unburnt hydrocarbons (smoke), oxides of nitrogen, carbon monoxide, and a few others. These are typically much lower level than when fossil fuels are combusted, but they remain a problem, particularly for the human health (ie may cause respiratory problems, certain cancers, ...).
 
[[Fuel|Zero-emissions fuels]] do not have this problem, yet are more difficult to use in practice, and are also more expensive.
 
Note that what is pollution for one [[technology]] may be the biofuel in another. For example, if wood is heated anaerobically (with limited oxygen), it produces carbon monoxide, which is normally considered a pollutant, but if collected, can be burnt as a biofuel.<ref>[http://www.ecoreality.org/wiki/Biofuel Biofuel]</ref>


==Types of biofuel==
==Types of biofuel==
===First generation biofuels===
===First generation biofuels===
'First-generation' or conventional biofuels are biofuels made from substances in crops (ie sugar, starch, and vegetable oil) that can be used for human consumption. Due to this, the production of fuel from these crops effectively creates problems in regards to the global food production.
'First-generation (or conventional) biofuels' are biofuels made from substances in crops (ie sugar, starch, and vegetable oil) that can be used for human consumption. Due to this, the production of fuel from these crops effectively creates problems in regards to the global food production.<ref>[https://sites.google.com/site/biofuelgenocide/ziegler-jean Jean Ziegler calling first generation biofuels a crime against humanity]</ref><ref>[http://en.wikipedia.org/wiki/Issues_relating_to_biofuels Issues relating to first and some second generation biofuels]</ref>
=====Bioalcohols=====
====Solid biofuels====
=====Biodiesel and green diesel=====
'''Solid biofuels''' are plant parts from crops grown for direct combustion. It includes [[wood]], [[sawdust]], [[grass]] trimmings, [[charcoal]], [[agricultural waste]], and [[dried manure]]. Some primary bio-energy feedstocks include industrial hemp, switchgrass and [[Miscanthus]]. They can be used as is or pressed into plates for easier incineration. Miscanthus or elephant grass generate a very high amount of dry matter.
=====Vegetable oil
====1st generation bioalcohols====
1.1.5 Bioethers
These include bio[[ethanol]], bio[[methanol]] and bio[[butanol]]. See [[Alcohols as fuel]].
1.1.6 Biogas
====Biodiesel and green diesel====
1.1.7 Syngas
See [[biodiesel]]
1.1.8 Solid biofuels
====Plant oils====
Second generation biofuels
These include pure plant oil (PPO) and waste plant oil (WPO), see [[Plant oils as fuel]]
 
*[[Algae]]
*[[Biodiesel]]
*[[Biogas]]
*[[Ethanol]]
*[[Gas pyrolisis]] (wood gas or poor gas)
*[[Biodigesters]]
*[[Methanol]]
*[[Wood]]
 
Second generation biofuels are biofuels produced from sustainable feedstock. Sustainability of a feedstock is defined among others by availability of the feedstock, impact on GHG emissions and impact on biodiversity and land use.[28] Many second generation biofuels are under development such as Cellulosic ethanol, Algae fuel[29]., biohydrogen, biomethanol, DMF, BioDME, Fischer-Tropsch diesel, biohydrogen diesel, mixed alcohols and wood diesel.
 
==Biofuels from cellulose - not yet economic==
:Scientists have long known how to turn trees into ethanol, but doing it profitably is another matter. We can run our cars on lawn cuttings today; we just can't do it at a price people are willing to pay.     
 
:The problem is cellulose. Found in plant cell walls, it's the most abundant naturally occurring organic molecule on the planet, a potentially limitless source of energy. But it's a tough molecule to break down...


:No one has yet figured out how to generate energy from plant matter at a competitive price. The result is that no car on the road today uses a drop of cellulosic ethanol. - [http://www.wired.com/science/planetearth/magazine/15-10/ff_plant Cellulosic Ethanol: One Molecule Could Cure Our Addiction to Oil], Evan Ratliff, ''Wired Magazine''  October 24, 2007. (The article continues, describing the history of attempts to transform cellulose, and current research.)
===Second generation biofuels===
'Second generation biofuels' are biofuels produced from made from substances in crops (ie cellulose) that can not be used for human consumption. Unlike first generation biofuels they do not create problems in regards to the global food production.
====Biogas====
See [[biogas]]
====Syngas====
See [[syngas]]
====2nd generation bioalcohols====
This includes ie [[biobutanol]], [[biomethanol]], bioethanol made from fruits, ... from crops that are not suitable to human consumption (ie poisonous crops) as well as cellulosic ethanol (ethanol made from woody plant parts (non-consumable plant parts of humanly edible crops) Woody plant parts can be converted to ethanol yet at present (2007 D.C.) it is not yet a economicly viable method.<ref>[http://www.wired.com/science/planetearth/magazine/15-10/ff_plant Cellulosic Ethanol: One Molecule Could Cure Our Addiction to Oil], Evan Ratliff, ''Wired Magazine''  October 24, 2007</ref>
====Wood gas====
See [[wood gas]]
====Algae fuel====
See [[algaculture]]
====Biohydrogen====
see [[Biohydrogen]]
====DMF====
====BioDME====
====Fischer-Tropsch diesel====
====Biohydrogen diesel====
====Mixed alcohols====
====Wood diesel====


==Biofuels in engines==
==Use==
With most biofuels the incompatibility with available engines provides an additional barrier to the adoption as reliable operation requires expensive engine modifications. 'flexi-fuel' engines are available in some regions, commonly spark ignition engines able to run straight petrol(US-gas) or petrol/ethanol blends.
With most biofuels the incompatibility with available engines provides an additional barrier to the adoption as reliable operation requires expensive engine modifications. 'Flexi-fuel' engines are available in some regions, commonly spark ignition engines able to run straight petrol(US-gas) or petrol/ethanol blends. [[Additives]] (bio ethers) can be applied to fuels to improve their performance.


Lists of the suitability of [[engines]] and [[engine components]]
===Use in heat engines ===
 
It is possible to use biofuels in several heat engines, including internal combustion engines (diesel, gasoline) and Stirling engines. Reliability and performance of the engine will depend on:
==Engines==
It is possible to use biofuels in numerous different types of engines. Reliability and performance of the engine will depend on:
* [[biofuel material compatibility]] - the compatability of fuel system and engine components to the fuel   
* [[biofuel material compatibility]] - the compatability of fuel system and engine components to the fuel   
* Engine parameters, such as fuel delivery or spark timing, being optimised for the given fuel
* engine parameters: such as fuel delivery or spark timing, being optimised for the given fuel
* a suitable maintenance regime
* a suitable maintenance regime


===Compressed Ignition or Diesel Engine===
====Use in IC engines (diesel engines)====
It is possible to use a wide range of biofuels in a diesel engine, most commonly lipid based biofuels are used either in their pure form, pure plant oil, or transesterified as biodiesel.
It is possible to use a wide range of liquid biofuels in a diesel engine, most commonly lipid based biofuels are used either in their pure form, [[plant oil]], or transesterified as [[biodiesel]]. [[Diesel engine fuel delivery]] can be altered to suit the fuel.
See also: http://en.wikipedia.org/wiki/Diesel_engine


[[Diesel engine fuel delivery]] can be altered to suit the fuel.
====Use in IC engines (gasoline engine) ====
Some liquid biofuels as ethanol can be used, oil-based biofuels can't be used though. Gases can also be used (ie [[wood gas]] (if filtered), [[biohydrogen]], [[biogas]] and pure [[methane]]) See http://en.wikipedia.org/wiki/Internal_combustion_engine


[http://en.wikipedia.org/wiki/Diesel_engine wikipedia diesel engine page]
====Use in Stirling engines ====
[[Stirling engine]]s can use a wide range of biofuels, both liquid biofuels (oils, ethanol, ...), solid biofuels (ie wood, seeds, ...) and gas-based biofuels (ie wood gas (if filtered), biohydrogen, biogas, pure methane )


===Spark Ignition, Petrol or Gas Engine===
====Use in steam and fuel-powered turbines====
[http://en.wikipedia.org/wiki/Internal_combustion_engine wikipedia internal combustion engine page detailing spark ignition and compressed ignition engines]
[[Fuel-powered turbine]]s can be run on liquid biofuels as oils, ethanol, ... as well as some gas-based biofuels (ie biohydrogen, methane). Gas-based biofuels as wood gas and biogas are potentially also possible, but could give problems with fouling (due to tar, ...) [[Steam turbine]]s (bladed-rotor, Tesla, ...) can run on all biofuels (solid, liquid, and gas-based biofuels). Fouling isn't a problem here (as opposed to fuel-powered turbines) as the heater chamber is generally separated from the chamber housing the turbine blades. Steam turbines however do require an additional energy conversion (fuel to steam) meaning there is some additional energy loss. The incineration of the fuel can btw be done using a [[pulse jet engine]] to increase efficiency, and to decrease fouling in this separate heating chamber (although it isn't a big problem) even more.


==Biofuels==
==References==
[[Additives]] can be applied to fuels to improve their performance
{{reflist}}


===Pure plant oils===
== External links ==
[[Pure plant oils]] - link to PPO main page
 
also known as straight vegetable oil (SVO) or when [[Used cooking oils and fats as diesel engine fuel|using used cooking oils]], waste vegetable oil (WVO).  The use of animal derived oils and fats uses the same principle.
 
Theoretically it is possible to modify any diesel engine to run on pure plant oils (PPO).  The modifications necessary to allow reliable operation vary greatly depending on the design of the engine, the type of oil to be burnt and the ambient temperatures in which the engine will be operated.
 
For reliable operation with PPO it is highly recommended to perform an [[engine health check]] before switching fuels as the use of PPO requires the engine to be in good order.
 
A widely used method for reliable operation is to convert the engine to dual fuel and fit a [[PPO two tank system]].  The engine is started on diesel fuel and switched to PPO as the engine warms.  Before the engine is stopped for an extended period the fuel supply is switched back to diesel fuel for enough time to allow the fuel system to be purged of PPO.  The engine is then ready to be cold started on diesel fuel.
 
It is possible however to modify cold start and fuelling parameters to allow engines to be started on PPO - this is known as a [[PPO single tank system]]
 
[http://en.wikipedia.org/wiki/Straight_vegetable_oil wikipedia SVO page]
 
===Biogas===
[http://en.wikipedia.org/wiki/Biogas wikipedia biogas page]
 
===Alcohol===
[http://en.wikipedia.org/wiki/Alcohol_fuel wikipedia alcohol page]
 
[http://www.permaculture.com/alcohol/index.shtml Alcohol can be a gas]
 
[http://web.archive.org/web/20060220145641/http://www.westbioenergy.org/reports/55032/55032final.htm Converting a vehicle to run on Ethanol]
 
[http://running_on_alcohol.tripod.com/id1.html Fuel Ethanol FAQ]
 
===Biodiesel===
[http://en.wikipedia.org/wiki/Biodiesel wikipedia biodiesel page]
 
[http://biodieseltutorial.utahbiodieselsupply.com/ Collaborative Biodiesel Tutorial]
 
[http://www.graham-laming.com/bd/main.htm] Some innovative DIY biodiesel equipment
 
===Wood gas===
{{Main|Wood gas}}
 
[http://www.woodgas.com/proximat.htm assessing differing feed stocks for woodgas systems]
 
[http://www.eng-tips.com/viewthread.cfm?qid=201009&page=2 Engine & fuel engineering - designing long-life engines for home biomass energy systems]
 
[http://www.vedbil.se/indexe.shtml Around Sweden with wood in the tank]
 
[http://www.gekgasifier.com/ Gasifier Experimenters Kit (GEK)]
 
== Interwiki links ==
* [[Wikipedia:Biofuel]]
* [[Wikipedia:Biofuel]]
 
* [http://obed.org.uk Open Biofuel Engine Development] - Collaborative biofuel engine tuning
== External links ==
* [http://www.builditsolar.com/Projects/Projects.htm Builtitsolar; has info on making some biofuels]
[http://obed.org.uk Open Biofuel Engine Development] - Collaborative biofuel engine tuning<br />
* [http://BioFuelBay.com Biofuel Bay] - Biofuel primer and educational resource
[http://BioFuelBay.com Biofuel Bay] - Biofuel primer and educational resource<br />
* [http://www.BioFuelDebate.com Biofuel Debate Forum] - Biofuel, Biodiesel and Bioenergy discussion forum
[http://www.BioFuelDebate.com Biofuel Debate Forum] - Biofuel, Biodiesel and Bioenergy discussion forum<br />
 
 
{{Needtopicadmin}}


[[Category:Transport]]
[[Category:Transport]]
[[Category:Renewable energy]]
[[Category:Renewable energy]]
[[Category:Waste management]]

Revision as of 08:36, 5 December 2017

Default.png
Default.png

Template:Lang Template:Content from

Biofuel is a term used to describe fuel sources that are derived from easily regeneratable animal or plant-based resources. Biofuels are categorically different from fossil fuels, as biofuel production is not based on the anaerobic decomposition of buried organic matter. Furthermore, fossil fuel deposits take millions of year to form and are a naturally occurring phenomenon while resources for biofuel production are usually considered renewable and are typically representative of the bi-product from some other production process. Biofuels are thus a form of closed-loop recycling recycling, as the waste product from some production process is re-appropriated in to fuel for the process itself. It should be noted that although biofuels vary greatly in nature from fossil fuels, they are both a form of indirect solar energy; the initial energetic input stored in these fuels originated from the sun and was captured via terrestrial primary production processes, or photosynthesis.

Biofuels can be divided in to two categories of First-generation and Second-generation:

First Generation Second Generation
Describes biofuels that are derived from the edible parts of plants. A consideration associated with this form of biofuel is that large-scale production involves the mass cultivation of crops (such as maize) that could be otherwise be inputted into the global food system. Valuable resources such as arable land are thus prioritized for fuel production, rather than food production. Describes biofuels that are derived from non-edible parts of plants, such as woody stems, branches, etc.[1] or from fruits that are not a part of the human diet. A benefit associated with second generation biofuels is that, unlike first generation processes, production is not inversely related to global food system production. Second-generation biofuel can be further divided in 2+ generation-biofuels and 2++ generation-biofuels
2+ generation-biofuel production involves no use of arable land at all for energy production (i.e. algae fuel)
2++ generation-biofuel production involves no use of arable land at all for energy production and no air pollution (this still occurs with the other biofuels, although there are no carbon emissions). (i.e. biohydrogen)


Background

Residual biomass can be re-appropriated without any primary treatment processes (i.e. the use of solid biomass) or be converted into various non-solid fuel forms; these forms are referred to as biogas and liquid biofuel. The purpose of such refinement processes is to improve the quality, specific energy content, transportability, etc., of the raw biomass source. It also allows for the capture of gases, which would otherwise be released in to the atmosphere, during natural biomass degradation processes. An example of this is the release of methane from anaerobic digestion in biomass waste or stockpiles. [2] These two forms of biofuel differ in there uses and applications; for example primary uses of biogas include cooking and lighting in a number of countries. On the other hand, development in liquid biofuel production has been driven by an ever-increasing societal need to displace fossil fuels as the default fuel source. Within the context of acknowledged and growing anthropogenic impact on the global energy system, there has been notable movement towards cultivation of energy crops specifically for the production of biomass-derived fuel. These developments are taking place globally, across Europe, the United States as well as in several developing countries; as the human population continues to accelerate towards both complete extraction of fossil fuels, as well as catastrophic atmospheric CO2 levels, the need for integrated energy supply options has become increasingly overt. This need for supplementary and renewable fuel sources has thus catalyzed development of biofuel technology and will furthermore be the basis for which biomass re-appropriation will reach its full potential as an energy source. In the following sections, a number of liquid biofuel forms will be outlined as well as their applications, and the conversion technologies used to derive them.

Environmental Considerations

There are two primary points of environmental concern, in relation to biomass-based energy derivation. The first point of concern is the potential for poor land management practices that are so often associated with any type fuel production. Examples of potential degrading production processes include large-scale implementation of mono-crops and the use of various chemical compounds to stimulate growth. Considerations specific to biofuel crop harvesting include the removal of plant residual material that would otherwise be broken down and increase the organic matter contentions and can furthermore contribute to greenhouse gas emissions through losses of soil carbon. [3]

However, land degradation and deforestation that could potentially be fostered by production of biofuels can be circumvented via cohesive and regulated land management policy. Furthermore, integration of non-conventional farming methodology, such as companion planting, IPM and conservation tillage into biofuel production policy could further reduce the potential for negative environmental impact associated with modern large-scale agricultural practices.

The second point of concern relates to the inversal nature of first generation fuel production and food production. This relationship was noted in the pervious sections. It arguable that such prioritization is not necessary, as much of the biomass requirement for energy production can be met through the re-appropriation of production bi-products (waste) or food industry residual material; you will remember that this form of biofuel is referred to as second generation. Policy infrastructure should thus be created with this consideration in mind, and limit the degree to which arable land and other production inputs can be employed for first generation biofuel production. Benefits to this limitation are two-fold, as it prevents undue stress on the environment related to biofuel production and restricts the degree to which this production can be prioritized over food production. For a more in depth outline of appropriate policy infrastructure, see [4].

The use of crops that are native to the region can also provide part of the answer. In addition to this, the exact place (and the current use of the location -ie food production, CO2 already locked in the soil, ...) where the crops are planted also matters. According to Wouter Achten of KU Leuven, biofuel-crops are best planted in CO2-poor soils and which are currently not used for agriculture. The first is for obvious reasons: by requiring the farmer to fertilise the soil with CO2 he locks away part of the CO2 in the atmosphere. The downside however is that extra fertilisation (and thus an increased cost) is required. The second is for less obvious reasons: if the land is used for agriculture, the crops that were planted need to be relocated. This could mean that there is an extra CO2-cost in transport (crops need to be transported further). This is known as ILUC.

Localised decentralised biofuel production from feedstock grown using sustainable agricultural practices been shown to offer part of a sustainable energy portfolio. A good example is for example rapeseed. This crop creates both biofuel (oil) as animal feed (the rest of the plant).

With the recent global call to reduce carbon dioxide emissions, there is a strong case for promoting the use of sustainable biomass-to-energy technologies worldwide. Using modern technology, enormous reductions can be made in carbon dioxide emissions, particularly if liquid biofuels are used to replace their fossil-based equivalents. In fact, if biomass energy production is done on a sustainable basis, there is little net carbon dioxide addition to the environment.

There are other environmental concerns related to each fuel that need to be kept in mind, such as toxic emissions and production of tars and soots.[5][6][7][8][9]

Advantages and disadvantages

Biofuels are not made from petroleum; not purchasing petroleum products allows you to avoid supporting business practices such as oil drilling that are harmful to the environment and human rights.

Pollution is any byproduct that cannot be fed back into the closed-end system. For biofuels (except for biohydrogen), this includes particulates and unburnt hydrocarbons (smoke), oxides of nitrogen, carbon monoxide, and a few others. These are typically much lower level than when fossil fuels are combusted, but they remain a problem, particularly for the human health (ie may cause respiratory problems, certain cancers, ...).

Zero-emissions fuels do not have this problem, yet are more difficult to use in practice, and are also more expensive.

Note that what is pollution for one technology may be the biofuel in another. For example, if wood is heated anaerobically (with limited oxygen), it produces carbon monoxide, which is normally considered a pollutant, but if collected, can be burnt as a biofuel.[10]

Types of biofuel

First generation biofuels

'First-generation (or conventional) biofuels' are biofuels made from substances in crops (ie sugar, starch, and vegetable oil) that can be used for human consumption. Due to this, the production of fuel from these crops effectively creates problems in regards to the global food production.[11][12]

Solid biofuels

Solid biofuels are plant parts from crops grown for direct combustion. It includes wood, sawdust, grass trimmings, charcoal, agricultural waste, and dried manure. Some primary bio-energy feedstocks include industrial hemp, switchgrass and Miscanthus. They can be used as is or pressed into plates for easier incineration. Miscanthus or elephant grass generate a very high amount of dry matter.

1st generation bioalcohols

These include bioethanol, biomethanol and biobutanol. See Alcohols as fuel.

Biodiesel and green diesel

See biodiesel

Plant oils

These include pure plant oil (PPO) and waste plant oil (WPO), see Plant oils as fuel

Second generation biofuels

'Second generation biofuels' are biofuels produced from made from substances in crops (ie cellulose) that can not be used for human consumption. Unlike first generation biofuels they do not create problems in regards to the global food production.

Biogas

See biogas

Syngas

See syngas

2nd generation bioalcohols

This includes ie biobutanol, biomethanol, bioethanol made from fruits, ... from crops that are not suitable to human consumption (ie poisonous crops) as well as cellulosic ethanol (ethanol made from woody plant parts (non-consumable plant parts of humanly edible crops) Woody plant parts can be converted to ethanol yet at present (2007 D.C.) it is not yet a economicly viable method.[13]

Wood gas

See wood gas

Algae fuel

See algaculture

Biohydrogen

see Biohydrogen

DMF

BioDME

Fischer-Tropsch diesel

Biohydrogen diesel

Mixed alcohols

Wood diesel

Use

With most biofuels the incompatibility with available engines provides an additional barrier to the adoption as reliable operation requires expensive engine modifications. 'Flexi-fuel' engines are available in some regions, commonly spark ignition engines able to run straight petrol(US-gas) or petrol/ethanol blends. Additives (bio ethers) can be applied to fuels to improve their performance.

Use in heat engines

It is possible to use biofuels in several heat engines, including internal combustion engines (diesel, gasoline) and Stirling engines. Reliability and performance of the engine will depend on:

  • biofuel material compatibility - the compatability of fuel system and engine components to the fuel
  • engine parameters: such as fuel delivery or spark timing, being optimised for the given fuel
  • a suitable maintenance regime

Use in IC engines (diesel engines)

It is possible to use a wide range of liquid biofuels in a diesel engine, most commonly lipid based biofuels are used either in their pure form, plant oil, or transesterified as biodiesel. Diesel engine fuel delivery can be altered to suit the fuel. See also: http://en.wikipedia.org/wiki/Diesel_engine

Use in IC engines (gasoline engine)

Some liquid biofuels as ethanol can be used, oil-based biofuels can't be used though. Gases can also be used (ie wood gas (if filtered), biohydrogen, biogas and pure methane) See http://en.wikipedia.org/wiki/Internal_combustion_engine

Use in Stirling engines

Stirling engines can use a wide range of biofuels, both liquid biofuels (oils, ethanol, ...), solid biofuels (ie wood, seeds, ...) and gas-based biofuels (ie wood gas (if filtered), biohydrogen, biogas, pure methane )

Use in steam and fuel-powered turbines

Fuel-powered turbines can be run on liquid biofuels as oils, ethanol, ... as well as some gas-based biofuels (ie biohydrogen, methane). Gas-based biofuels as wood gas and biogas are potentially also possible, but could give problems with fouling (due to tar, ...) Steam turbines (bladed-rotor, Tesla, ...) can run on all biofuels (solid, liquid, and gas-based biofuels). Fouling isn't a problem here (as opposed to fuel-powered turbines) as the heater chamber is generally separated from the chamber housing the turbine blades. Steam turbines however do require an additional energy conversion (fuel to steam) meaning there is some additional energy loss. The incineration of the fuel can btw be done using a pulse jet engine to increase efficiency, and to decrease fouling in this separate heating chamber (although it isn't a big problem) even more.

References

Template:Reflist

External links

  1. ↑ also called cellulosic alcohol
  2. ↑ Methane and nitrous oxide emissions from biomass waste stockpiles. BTG biomass technology group BV, 2002.
  3. ↑ The State of Food and Agriculture. United Nations, 2008
  4. ↑ Negussie, A., Verbist, B.J.P. & Muys, B. (2014). Invasiveness prospects of Biofuels: avoid invasiveness threat of novel tropical biofuel crops. KLIMOS-Policy Brief 7, KLIMOS, Leuven.
  5. ↑ Anderson, T., Doig, A., Rees, D. and Khennas, S., Rural Energy Services: A handbook for sustainable energy development. ITDG Publishing, 1999.
  6. ↑ Ravindranath, N. H. and Hall, D. O., Biomass, Energy and the Environment: A Developing Country Perspective from India. Oxford University Press, 1995.
  7. ↑ Karekezi, S. and Ranja, T., Renewable Energy Technologies in Africa. AFREPEN, 1997.
  8. ↑ Kristoferson L. A., and Bokalders V., Renewable Energy Technologies - their application in developing countries. ITDG Publishing, 1991.
  9. ↑ Johansen, T.B. et al, Renewable Energy Sources for Fuels and Electricity. Island Press, Washington D.C., 1993.
  10. ↑ Biofuel
  11. ↑ Jean Ziegler calling first generation biofuels a crime against humanity
  12. ↑ Issues relating to first and some second generation biofuels
  13. ↑ Cellulosic Ethanol: One Molecule Could Cure Our Addiction to Oil, Evan Ratliff, Wired Magazine October 24, 2007
Retrieved from "https://www.appropedia.org/w/index.php?title=Biofuel&oldid=358775"
Cookies help us deliver our services. By using our services, you agree to our use of cookies.