Biogas
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225363596
2008-07-13T08:29:56Z
Joseph Solis in Australia
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[[Image:Biogas pipes.JPG|right|thumbnail|300px|Pipes carrying biogas]]
'''Biogas''' typically refers to a [[gas]] produced by the biological breakdown of [[organic matter]] in the absence of oxygen. Biogas originates from biogenic material and is a type of [[biofuel]]. One type of biogas is produced by [[anaerobic digestion]] or [[fermentation (biochemistry)|fermentation]] of biodegradable materials such as [[biomass]], [[manure]] or [[sewage]], [[municipal waste]], and [[energy crop]]s. This type of biogas comprises primarily [[methane]] and [[carbon dioxide]]. The other principal type of biogas is [[wood gas]] which is created by gasification of wood or other biomass. This type of biogas is comprised primarily of [[nitrogen]], [[hydrogen]], and [[carbon monoxide]], with trace amounts of [[methane]].
The gases methane, hydrogen and carbon monoxide can be combusted or oxidized with oxygen. Air contains 21% oxygen. This energy release allows biogas to be used as a fuel. Biogas can be used as a low-cost fuel in any country for any heating purpose, such as cooking. It can also be utilized in modern [[waste management]] facilities where it can be used to run any type of [[heat engine]], to generate either mechanical or electrical power. Biogas is a [[renewable fuel]] and electricity produced from it can be used to attract renewable energy subsidies in some parts of the world.
==Production==
{{main|anaerobic digestion}}
[[Image:Biogasholder and flare.JPG|right|thumbnail|300px|Biogas holder and flare]]
Depending on where it is produced, biogas can also be called [[swamp]], [[marsh]], [[landfill]] or [[anaerobic digester|digester]] gas. A biogas plant is the name often given to an anaerobic digester that treats farm wastes or energy crops.
Biogas can be produced utilizing anaerobic digesters. These plants can be fed with energy crops such as maize silage or [[biodegradable waste]]s including sewage sludge and food waste.
Landfill gas is produced by organic waste decomposing under anaerobic conditions in a landfill. The waste is covered and compressed mechanically and by the weight of the material that is deposited from above. This material prevents oxygen from accessing the waste and anaerobic microbes thrive. This gas builds up and is slowly released into the atmosphere if the landfill site has not been engineered to capture the gas. Landfill gas is hazardous for three key reasons. Landfill gas becomes explosive when it escapes from the landfill and mixes with oxygen within lower and higher explosive limits. The methane in biogas forms explosive mixtures in air. The lower explosive limit is 5% methane and the upper explosive limit is 15% methane.<ref>[http://www.adelaide.edu.au/biogas/safety/ Safety Page, Beginners Guide to Biogas], www.adelaide.edu.au/biogas, retrieved 22.10.07</ref> The methane contained within biogas is 20 times more potent as a greenhouse gas than carbon dioxide. Therefore uncontained landfill gas which escapes into the atmosphere may significantly contribute to the effects of global warming. In addition to this [[volatile organic compound]]s (VOCs) contained within landfill gas contribute to the formation of [[photochemical smog]].
Sweden produces biogas from confiscated alcoholic beverages. [http://www.sweden.se/templates/cs/Article____14363.aspx]
==Composition==
{| class="wikitable" style="float: right; margin-left: 10px"
|+ '''Typical composition of biogas'''<ref>[http://www.kolumbus.fi/suomen.biokaasukeskus/en/enperus.html Basic Information on Biogas], www.kolumbus.fi, retrieved 2.11.07</ref>
|-
! style=“background-color: # cfb;” | Matter
! style=“background-color: # cfb;” | %
|-
! Methane, CH<sub>4</sub>
| 50-75
|-
! Carbon dioxide, CO<sub>2</sub>
| 25-50
|-
! Nitrogen, N<sub>2</sub>
| 0-10
|-
! Hydrogen, H<sub>2</sub>
| 0-1
|-
! Hydrogen sulfide, H<sub>2</sub>S
| 0-3
|-
! Oxygen, O<sub>2</sub>
| 0-2
|-
|}
The composition of biogas varies depending upon the origin of the anaerobic digestion process. Landfill gas typically has methane concentrations around 50%. Advanced waste treatment technologies can produce biogas with 55-75%CH<sub>4</sub> <ref>[http://www.oaktech-environmental.com/Juniper.htm Juniper Biogas Yield Comparison]</ref>.
{{main|Siloxanes}}
In some cases biogas contains [[siloxane]]s. These siloxanes are formed from the anaerobic decomposition of materials commonly found in soaps and detergents. During combustion of biogas containing siloxanes, silicon is released and can combine with free oxygen or various other elements in the combustion gas. Deposits are formed containing mostly [[silica]] (<math>SiO_{2}</math>) or [[silicates]] (<math>Si_{x}O_{y}</math>) and can also contain calcium, sulfur, zinc, phosphorus. These white mineral deposits build to a surface thickness of several millimetres and must be removed by chemical or mechanical means.
==Applications==
Biogas can be utilized for electricity production, cooking, space heating, [[water heating]] and process heating. If compressed, it can replace [[compressed natural gas]] for use in vehicles, where it can fuel an [[internal combustion engine]] or [[fuel cell]]s.
Methane within biogas can be concentrated to the same standards as [[natural gas]], when it is, it is called biomethane. If the local gas network permits it the producer of the biogas may be able to utilize the local gas distribution networks. Gas must be very clean to reach pipeline quality, and must be of the correct composition for the local distribution network to accept. [[Carbon dioxide]], [[Water]], [[hydrogen sulfide]] and [[particulate]]s must be removed if present. If concentrated and compressed it can also be used in vehicle transportation. Compressed biogas is becoming widely used in Sweden, Switzerland and Germany. A biogas-powered train has been in service in Sweden since 2005.<ref>[http://www.svenskbiogas.se/sb/docs/english/Biogastrain_produktblad_2005.pdf Biogas train in Sweden]</ref><ref>Friendly fuel trains (Oct. 30, 2005) [[New Straits Times]], p. F17.</ref>
Bates' and his biogas car were the subject of a short documentary film called 'Sweet as a Nut' in 1974, at which point he had run his car for 17 years on gas he had produced by processing pig manure. Bates, an inventor, lived in Devon, UK and in the film talks through the simple process and benefits of running a car on biogas. The conversion was simply made with an adapter attached to any combustion engine.
==Biogas in developing nations==
In India biogas produced from the anaerobic digestion of [[manure]] in small-scale digestion facilities is called [[Gober gas]]. In India biogas is generated at an estimated 2 million+ household facilities. The digester is an airtight circular pit made of concrete with a pipe connection. The manure is directed to the pit, usually directly from the cattle shed. The pit is then filled with a required quantity of [[wastewater]]. The gas pipe is connected to the kitchen fire place through control valves. The combustion of this biogas has very little odour or smoke. Owing to simplicity in implementation and use of cheap raw materials in villages, it is one of the most environmentally sound energy sources for rural needs.
Biogas is used extensively throughout rural China and where wastewater treatment and industry coincide. <ref>[http://www.i-sis.org.uk/BiogasChina.php "Biogas China" in ''ISIS'']</ref>
The Biogas Support Program in Nepal has installed over 100,000 biogas plants in rural areas. <ref>[http://www.aepcnepal.org/gen/bio.php Biogas Support Program in Nepal]</ref>
Vietnam’s Biogas Programme for Animal Husbandry Sector has led to the installation of over 20,000 plants throughout that country. <ref>[http://www.snv.org.vn/NewDetail.Asp?ID=111&Show=3&SubId=2 Vietnam’s Biogas Programme for Animal Husbandry Sector]</ref>
Biogas is also in use in rural Costa Rica.<ref>[http://www.ruralcostarica.com/biogas-faqs.html Biogas in Rural Costa Rica]</ref>
In Colombia experiments with diesel engines-generator sets partially fuelled by biogas demonstrated that biogas could be used for power generation, reducing elecricity costs by 40% compared with purchase from the regional utility. <ref>[http://www.cipav.org.co/cipav/resrch/energy/alvaro1.htm Generation of electricty from biogas, experiments at Pozo Verde farm, Valle del Cauca, Colombia]
</ref>
==Legislation==
The European Union presently has some of the strictest legislation regarding waste management and landfill sites called the [[Landfill Directive]]. The United States legislates against landfill gas as it contains these VOCs. The United States Clean Air Act and Title 40 of the Code of Federal Regulations (CFR) requires landfill owners to estimate the quantity of non-methane organic compounds (NMOCs) emitted. If the estimated NMOC emissions exceeds 50 tonnes per year the landfill owner is required to collect the landfill gas and treat it to remove the entrained NMOCs. Treatment of the landfill gas is usually by combustion. Because of the remoteness of landfill sites it is sometimes not economically feasible to produce electricity from the gas.
==Gober gas==
[[Image:Gobar Gober Gas Plant 2.jpg|thumb|Manure is in regular supply]][[Image:Gobar Gober Gas Plant 4.jpg|thumb|Airtight circular cylinder, which moves up and down depending upon the collection of gas]]
'''Gober gas''' (also spelled as "Gobar gas" by some) is biogas generated out of [[cow dung]]. In [[India]], gober gas is generated at the countless number of micro plants (an estimated more than 2 million) attached to households. In Pakistan the concept is also quickly growing. The Government of Pakistan provides 50% funds for the construction of moveable gas chamber biogas plants{{Fact|date=July 2008}}. The gober gas plant is an airtight circular pit made of [[concrete]] with a pipe connection. The [[manure]] is directed to the pit, usually directly from the cattle shed. The pit is then filled with a required quantity of water or wastewater. The gas pipe is connected to the kitchen fire place through control valves. The flammable methane gas generated out of this is largely odourless and smokeless. The residue left after the extraction of the gas is used as fertiliser. Owing to its simplicity in implementation and use of cheap raw materials in the villages, it is often quoted as one of the most environmentally sound energy source for the rural needs.<ref>[http://www.mothercow.org/oxen/gobar-gas-methane.html Gobar Gas Methane Experiments in India], www.mothercow.org, retrieved 30.06.08</ref><ref>[http://www.habmigern2003.info/biogas/methane-digester.html Biogas production], www.habmigern2003,info, retrieved 30.06.08</ref> <ref>http://www.ecouncil.ac.cr/rio/focus/report/english/inforse.htm Biogas in India: A Sustainable Energy Success Story], www.ecouncil.ac.cr, retrieved 30.06.08</ref>
==See also==
{{Portalpar|Sustainable development|Sustainable development.svg}}
{{EnergyPortal}}
*[[Biodegradability]]
*[[Bioenergy]]
*[[Biofuel]]
*[[Landfill gas monitoring]]
*[[MSW/LFG]] (municipal solid waste and landfill gas)
*[[NGV|Natural gas vehicle]]
*[[Renewable energy]]
*[[Renewable natural gas]]
*[[Tables of European biogas utilisation]]
*[[Waste management]]
==References==
{{reflist}}
==External links==
*[http://www.adelaide.edu.au/biogas/ An Introduction to Biogas, University of Adelaide]
*[http://www.rccostello.com/naturalgas.html Biogas purification]
*[http://www.ruralcostarica.com/biogas.html Biogas in rural Costa Rica]
*[http://www.completebiogas.com/ The Biogas Handbook: Several chapters available for download]
*[http://www.gasforeningen.se/upload/files/publikationer/rapporter/biogasinfo%20eng%202008%20sammansatt.pdf Biogas from manure and waste products - Swedish case studies]
[[Category:Anaerobic digestion]]
[[Category:Bioenergy]]
[[Category:Biodegradation]]
[[Category:Biotechnology products]]
[[Category:Biodegradable waste management]]
[[Category:Landfill]]
[[Category:Fuels]]
[[Category:Fuel gas]]
[[Category:Methane]]
[[Category:Waste management]]
[[Category:Energy sources]]
[[Category:Energy in India]]
[[Category:Biofuel in India]]
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