View source for Biofuel

{{Short description|Fuel derived from biological sources}}
{{cs1 config|name-list-style=vanc|display-authors=6}}
{{About|mainly liquid or gaseous fuels used for transport|other applications|Bioenergy}}
{{Use dmy dates|date=June 2020}}
[[File:Biodiesel.JPG|thumb|upright|A sample of [[biodiesel]]]]
{{Renewable energy sources}} 
'''Biofuel''' is a [[fuel]] that is produced over a short time span from [[Biomass (energy)|biomass]], rather than by the very slow natural processes involved in the formation of [[fossil fuel]]s such as oil.<ref>{{cite book |last1=Priya |first1=Anshu |last2=Hu |first2=Yunzi |last3=Mou |first3=Jinhua |last4=Du |first4=Chenyu |last5=Wilson |first5=Karen |last6=Luque |first6=Rafael |last7=Lin |first7=Carol Sze Ki |editor1-last=Luque |editor1-first=Rafael |editor2-last=Sze Ki Lin |editor2-first=Carol |editor3-last=Wilson |editor3-first=Karen |editor4-last=Du |editor4-first=Chenyu |title=Handbook of Biofuels Production |date=2023 |publisher=[[Woodhead Publishing]] |isbn=978-0-323-91193-1 |pages=3–24 |chapter=Chapter 1 - Introduction: An overview of biofuels and production technologies |edition=Third |doi=10.1016/B978-0-323-91193-1.00002-0}}</ref> Biofuel can be produced from plants or from agricultural, domestic or industrial [[Biodegradable waste|bio waste]].<ref>{{Cite web |date=2024-03-18 |title=Biofuel {{!}} Definition, Types, & Pros and Cons {{!}} Britannica |url=https://www.britannica.com/technology/biofuel |access-date=2024-04-02 |website=www.britannica.com |language=en}}</ref><ref>{{cite journal |last1=Mahapatra |first1=Sangita |last2=Kumar |first2=Dilip |last3=Singh |first3=Brajesh |last4=Sachan |first4=Pravin Kumar |title=Biofuels and their sources of production: A review on cleaner sustainable alternative against conventional fuel, in the framework of the food and energy nexus |journal=Energy Nexus |date=2021 |volume=4 |article-number=100036 |doi=10.1016/j.nexus.2021.100036 |doi-access=free|bibcode=2021EnNex...4j0036M }}</ref><ref>{{cite journal |last1=Malode |first1=Shweta J. |last2=Prabhu |first2=K. Keerthi |last3=Mascarenhas |first3=Ronald J. |last4=Shetti |first4=Nagaraj P. |last5=Aminabhavi |first5=Tejraj M. |title=Recent advances and viability in biofuel production |journal=Energy Conversion and Management: X |date=2021 |volume=10 |article-number=100070 |doi=10.1016/j.ecmx.2020.100070 |doi-access=free|bibcode=2021ECMX...1000070M }}</ref><ref>{{cite journal |last1=Cherwoo |first1=Lubhan |last2=Gupta |first2=Ishika |last3=Flora |first3=G. |last4=Verma |first4=Ritu |last5=Kapil |first5=Muskaan |last6=Arya |first6=Shailendra Kumar |last7=Ravindran |first7=Balasubramani |last8=Khoo |first8=Kuan Shiong |last9=Bhatia |first9=Shashi Kant |last10=Chang |first10=Soon Woong |last11=Ngamcharussrivichai |first11=Chawalit |last12=Ashokkumar |first12=Veeramuthu |title=Biofuels an alternative to traditional fossil fuels: A comprehensive review |journal=Sustainable Energy Technologies and Assessments |date=2023 |volume=60 |article-number=103503 |doi=10.1016/j.seta.2023.103503|bibcode=2023SETA...6003503C }}</ref> Biofuels are mostly used for transportation, but can also be used for heating and electricity.<ref name="mw-2020" />{{rp|173}}<ref name="www.eia.gov-2023" /> Biofuels (and [[bioenergy|bio energy]] in general) are regarded as a [[renewable energy]] source.<ref name="Letcher chapter 1" />{{rp|11}} The use of biofuel has been subject to criticism regarding the "[[food vs fuel]]" debate, varied assessments of their [[Sustainable biofuel|sustainability]], and ongoing [[deforestation]] and [[biodiversity loss]] as a result of biofuel production.<ref>{{cite journal |last1=Lade |first1=Gabriel E. |last2=Smith |first2=Aaron |title=Biofuels: Past, Present, and Future |journal=Annual Review of Resource Economics |date=2025 |volume=17 |issue=1 |pages=105–125 |doi=10.1146/annurev-resource-011724-082950 |bibcode=2025ARRE...17..105L |doi-access=free}}</ref>

In general, biofuels emit fewer [[greenhouse gas emissions]] when burned in an engine and are generally considered [[carbon-neutral fuel]]s as the carbon emitted has been captured from the atmosphere by the crops used in production.<ref name="Lewandrowski Rosenfeld Pape Hendrickson pp. 361–375" /> However, [[life-cycle assessment]]s of biofuels have shown large emissions associated with the potential [[land-use change]] required to produce additional biofuel feedstocks.<ref name="Jeswani-2020" /><ref name="Lark Hendricks Smith Pates 2022 p." /> The outcomes of lifecycle assessments (LCAs) for biofuels are highly situational and dependent on many factors including the type of feedstock, production routes, data variations, and methodological choices.<ref>{{Cite journal |last1=Jeswani |first1=Harish K. |last2=Chilvers |first2=Andrew |last3=Azapagic |first3=Adisa |date=November 2020 |title=Environmental sustainability of biofuels: a review |journal=Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences |language=en |volume=476 |issue=2243 |article-number=20200351 |doi=10.1098/rspa.2020.0351 |pmc=7735313 |pmid=33363439 |bibcode=2020RSPSA.47600351J }}</ref> Estimates about the climate impact from biofuels vary widely based on the methodology and exact situation examined.<ref name="Jeswani-2020" /> Therefore, the [[climate change mitigation]] potential of biofuel varies considerably: in some scenarios emission levels are comparable to fossil fuels, and in other scenarios the biofuel emissions result in [[Negative emissions technologies|negative emissions]].

Global demand for biofuels is predicted to increase by 56% over 2022–2027.<ref name=":0">{{Cite news |date=2023-01-23 |title=Biofuel is approaching a feedstock crunch. How bad? And what must be done? |url=https://energypost.eu/biofuel-is-approaching-a-feedstock-crunch-how-bad-and-what-must-be-done/ |access-date=2024-03-14 |website=Energy Post |language=en-GB}}</ref> By 2027 worldwide biofuel production is expected to supply 5.4% of the world's fuels for transport including 1% of aviation fuel.<ref name="IEA-2022" /> Demand for [[aviation biofuel]] is forecast to increase.<ref name=":1">{{Cite news |date=2023-01-23 |title=Biofuel is approaching a feedstock crunch. How bad? And what must be done? |url=https://energypost.eu/biofuel-is-approaching-a-feedstock-crunch-how-bad-and-what-must-be-done/ |access-date=2023-01-30 |website=Energy Post |language=en-GB}}</ref><ref>{{Cite web |title=How to scale Sustainable Aviation Fuel in the next decade |url=https://www.weforum.org/agenda/2023/01/scale-sustainable-aviation-fuel-in-the-next-decade-davos23/ |access-date=2023-01-30 |website=World Economic Forum |language=en}}</ref> However some policy has been criticised for favoring ground transportation over aviation.<ref>{{Cite web |title=More Electric Cars Are Key To Meeting SAF Targets, Boeing Says {{!}} Aviation Week Network |url=https://aviationweek.com/special-topics/sustainability/more-electric-cars-are-key-meeting-saf-targets-boeing-says |access-date=2024-09-16 |website=aviationweek.com}}</ref>

The two most common types of biofuel are [[Ethanol#Fuel|bioethanol]] and [[biodiesel]]. Brazil is the largest producer of bioethanol, while the EU is the largest producer of biodiesel. The energy content in the global production of bioethanol and biodiesel is 2.2 and 1.8 EJ per year, respectively.<ref name="IEA 2022">{{cite web | title=Renewables Report 2022 | website=IEA | date=6 December 2022 | url = https://www.iea.org/reports/renewables-2022}}</ref>

Bioethanol is an [[Alcohol (chemistry)|alcohol]] made by [[Ethanol fermentation|fermentation]], mostly from [[carbohydrate]]s produced in [[sugar]] or [[starch]] crops such as [[maize]], [[sugarcane]], or [[sweet sorghum]]. [[Cellulose|Cellulosic biomass]], derived from non-food sources, such as trees and grasses, is also being developed as a [[feedstock]] for ethanol production. Ethanol can be used as a fuel for vehicles in its pure form (E100), but it is usually used as a [[gasoline]] [[Fuel additive|additive]] to increase octane ratings and improve vehicle emissions.

Biodiesel is produced from oils or fats using [[transesterification]]. It can be used as a fuel for vehicles in its pure form (B100), but it is usually used as a [[diesel fuel|diesel]] additive to reduce levels of particulates, [[carbon monoxide]], and [[hydrocarbon]]s from diesel-powered vehicles.<ref>{{Cite journal | vauthors = Bayetero CM, Yépez CM, Cevallos IB, Rueda EH |date= January 2022 |title=Effect of the use of additives in biodiesel blends on the performance and opacity of a diesel engine |journal=Materials Today: Proceedings |series=Advances in Mechanical Engineering Trends |volume=49 |pages=93–99 |doi=10.1016/j.matpr.2021.07.478 |doi-access=free }}</ref>{{TOC limit|3}}

== Terminology ==
{{See also|Biomass (energy)#Terminology}}
[[File:Types and generation of biofuels.png|thumb|upright=1.2|Types and generation of biofuels]]
The term ''biofuel'' is used in different ways. One definition is "Biofuels are biobased products, in solid, liquid, or gaseous forms. They are produced from crops or natural products, such as wood, or agricultural residues, such as molasses and bagasse."<ref name="mw-2020">{{Cite book |title=Future energy: improved, sustainable and clean options for our planet |date=2020 |editor=T. M. Letcher |isbn=978-0-08-102887-2 |edition=3rd |location=Amsterdam, Netherlands |chapter=Chapter 9: Biofuels for transport |oclc=1137604985}}</ref>{{rp|173}}

Other publications reserve the term biofuel for ''liquid'' or ''gaseous'' fuels, used for transportation.<ref name="www.eia.gov-2023">{{Cite web |title=Biofuels explained - U.S. Energy Information Administration (EIA) |url=https://www.eia.gov/energyexplained/biofuels/ |access-date=2023-01-24 |website=www.eia.gov}}</ref>

The [[IPCC Sixth Assessment Report]] defines ''biofuel'' as "A fuel, generally in liquid form, produced from [[Biomass (energy)|biomass]]. Biofuels include [[bioethanol]] from sugarcane, sugar beet or maize, and [[biodiesel]] from canola or soybeans.".<ref name="ipcc_glossary">IPCC, 2022: [https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_AnnexVII.pdf Annex I: Glossary] [van Diemen, R., J.B.R. Matthews, V. Möller, J.S. Fuglestvedt, V. Masson-Delmotte, C.  Méndez, A. Reisinger, S. Semenov (eds)]. In IPCC, 2022: [https://www.ipcc.ch/report/ar6/wg3/ Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] [P.R. Shukla, J. Skea, R. Slade, A. Al Khourdajie, R. van Diemen, D. McCollum, M. Pathak, S. Some, P. Vyas, R. Fradera, M. Belkacemi, A. Hasija, G. Lisboa, S. Luz, J. Malley, (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA. doi: 10.1017/9781009157926.020</ref>{{rp|1795}} It goes on to define ''biomass'' in this context as "organic material excluding the material that is fossilised or embedded in geological formations".<ref name="ipcc_glossary" />{{rp|1795}} This means that [[coal]] or other [[fossil fuel]]s is not a form of biomass in this context.

=== Conventional biofuels (first generation)  ===
''First-generation biofuels'' (also denoted as "conventional biofuels") are made from food crops grown on arable land.<ref>{{Cite journal |last1=Cavelius |first1=Philipp |last2=Engelhart-Straub |first2=Selina |last3=Mehlmer |first3=Norbert |last4=Lercher |first4=Johannes |last5=Awad |first5=Dania |last6=Brück |first6=Thomas |date=2023-03-30 |title=The potential of biofuels from first to fourth generation |journal=PLOS Biology |language=en |volume=21 |issue=3 |article-number=e3002063 |doi=10.1371/journal.pbio.3002063 |doi-access=free |pmc=10063169 |pmid=36996247}}</ref><ref name="Letcher_ch21">{{Cite book |title=Future energy: improved, sustainable and clean options for our planet |date=2020 |editor=T. M. Letcher |isbn=978-0-08-102887-2 |edition=3rd |location=Amsterdam, Netherlands |chapter=Chapter 21: Energy from biomass |oclc=1137604985}}</ref>{{rp|447}} The crop's sugar, starch, or oil content is converted into [[biodiesel]] or [[ethanol]], using [[transesterification]], or yeast fermentation.<ref name="bio">{{Cite web|url=http://www.biofuelsdigest.com/bdigest/2010/05/18/3g-4g-a-taxonomy-for-far-out-%E2%80%94-but-not-far-away-%E2%80%94-biofuels/|title=What are – and who's making – 2G, 3G and 4G biofuels?: Biofuels Digest - biofuels, biodiesel, ethanol, algae, jatropha, green gasoline, green diesel, and biocrude daily news|date=21 May 2010|archive-url=https://web.archive.org/web/20100521143237/http://www.biofuelsdigest.com/bdigest/2010/05/18/3g-4g-a-taxonomy-for-far-out-%E2%80%94-but-not-far-away-%E2%80%94-biofuels/|archive-date=21 May 2010}}</ref>

=== Advanced biofuels ===
To avoid a "[[Food vs. fuel|food versus fuel]]" dilemma, [[second-generation biofuels]] and third-generation biofuels (also called [[Advanced Biofuels|advanced biofuels]] or [[sustainable biofuel]]s or drop-in biofuels) are made from feedstocks which do not directly compete with food or feed crop such as waste products and energy crops.<ref>{{Cite web |last=European Parliament |title=Advanced biofuels |url=https://www.europarl.europa.eu/RegData/etudes/BRIE/2017/603972/EPRS_BRI(2017)603972_EN.pdf |access-date=19 April 2024}}</ref> A wide range of renewable residue feedstocks such as those derived from agriculture and forestry activities like rice straw, rice husk, wood chips, and sawdust can be used to produce advanced biofuels through biochemical and thermochemical processes.<ref name="Letcher_ch21" />{{rp|448}}g<ref>{{cite book |title=The Microbiology of the Drop-in Biofuel Production |chapter=Renewable Residues as Feedstock for Drop-in Biofuel Production |series=Biofuel and Biorefinery Technologies |date=2024 |volume=15 |pages=41–74 |doi=10.1007/978-3-031-61637-2_3 |isbn=978-3-031-61636-5 | vauthors = Flores LF, Osorio-Gonzalez CS, Saini R, Brar SK }}</ref>

The feedstock used to make the fuels either grow on [[arable land]] but are byproducts of the main crop, or they are grown on marginal land. Second-generation feedstocks also include straw, bagasse, perennial grasses, jatropha, waste vegetable oil, municipal solid waste and so forth.<ref>{{Cite web|url=http://biofuel.org.uk/second-generation-biofuels.html|title=Biofuels – Second Generation Biofuels|website=biofuel.org.uk|access-date=18 January 2018|archive-date=15 July 2019|archive-url=https://web.archive.org/web/20190715112931/http://biofuel.org.uk/second-generation-biofuels.html|url-status=live}}</ref>

==Types ==

=== Liquid ===

==== Ethanol ====

{{Main|Ethanol fuel}}

Biologically produced [[alcohols]], most commonly ethanol, and less commonly [[Propan-1-ol|propanol]] and [[butanol fuel|butanol]], are produced by the action of [[microorganism]]s and [[enzyme]]s through the fermentation of sugars or starches (easiest to produce) or cellulose (more difficult to produce).The IEA estimates that ethanol production used 20% of sugar supplies and 13% of corn supplies in 2021.<ref name="Renewables 2022 Biofuels">{{Cite web |title=Is the biofuel industry approaching a feedstock crunch? – Analysis |url=https://www.iea.org/reports/is-the-biofuel-industry-approaching-a-feedstock-crunch |access-date=2023-01-02 |website=IEA |date=6 December 2022 |language=en-GB}}</ref>

Ethanol fuel is the most common biofuel worldwide, particularly [[Ethanol fuel in Brazil|in Brazil]]. [[Alcohol fuel]]s are produced by fermentation of sugars derived from [[wheat]], [[Maize|corn]], [[sugar beet]]s, [[sugar cane]], [[molasses]] and any sugar or starch from which [[alcoholic beverage]]s such as [[whiskey]], can be made (such as [[potato]] and [[fruit]] waste, etc.). Production methods used are [[digestive enzyme|enzyme digestion]] (to release sugars from stored starches), fermentation of the sugars, [[distillation]] and drying. The distillation process requires significant energy input to generate heat. Heat is sometimes generated with unsustainable [[natural gas]] fossil fuel, but cellulosic biomass such as [[bagasse]] is the most common fuel in Brazil, while pellets, wood chips and also [[waste heat]] are more common in Europe. Corn-to-ethanol and other food stocks has led to the development of [[cellulosic ethanol]].<ref>{{cite report |title=Breaking the biological barriers to cellulosic ethanol: a joint research agenda. |date=7 June 2006 |publisher=EERE Publication and Product Library |doi=10.2172/1218382 |location=Washington, DC (United States) |vauthors=Houghton J, Weatherwax S, Ferrell J}}</ref> Ethanol fuel can be combined with gasoline to create a more environmentally friendly fuel though there are more viable substitutions to gasoline such as [[Butanol fuel|Butanol]].<ref>{{cite journal |last1=Padder |first1=Shahid Ahmad |last2=Khan |first2=Rabia |last3=Rather |first3=Rauoof Ahmad |title=Biofuel generations: New insights into challenges and opportunities in their microbe-derived industrial production |journal=Biomass and Bioenergy |date=June 2024 |volume=185 |article-number=107220 |doi=10.1016/j.biombioe.2024.107220 |bibcode=2024BmBe..18507220P }}</ref>  

==== Other biofuels ====

Methanol is currently produced from [[natural gas]], a [[non-renewable]] fossil fuel. In the future it is hoped to be produced from biomass as [[biomethanol]]. This is technically feasible, but the production is currently being postponed for concerns that the economic viability is still pending.<ref>{{cite report |title=Dagens och framtidens hållbara biodrivmedel: underlagsrapport från f3 till utredningen om fossilfri fordonstrafik. |date=18 June 2013 |publisher=The Swedish Knowledge Centre for Renewable Transportation Fuels |volume=13 |page=170 |language=Swedish |vauthors=Börjesson P, Lundgren J, Ahlgren S, Nyström I |trans-title=Today's and the future's sustainable biofuels: background report from f3 to the inquiry into fossil-free vehicle traffic.}}</ref> The [[methanol economy]] is an alternative to the [[hydrogen economy]] to be contrasted with today's [[hydrogen]] production from natural gas.

[[Butanol fuel|Butanol]] ({{chem|C|4|H|9|OH}}) is formed by [[Clostridium acetobutylicum|ABE fermentation]] (acetone, butanol, ethanol) and experimental modifications of the process show potentially high [[net energy gain]]s with [[biobutanol]] as the only liquid product. Biobutanol is often claimed to provide a direct replacement for gasoline, because it will produce more energy than ethanol and allegedly can be burned "straight" in existing gasoline engines (without modification to the engine or car),<ref>{{cite web |date=15 August 2005 |title=ButylFuel, LLC Main Page |url=http://www.butanol.com/ |url-status=live |archive-url=https://web.archive.org/web/20190710235804/http://www.butanol.com/ |archive-date=10 July 2019 |access-date=14 July 2010 |publisher=Butanol.com}}</ref> is less corrosive and less water-soluble than ethanol, and could be distributed via existing infrastructures. ''[[Escherichia coli]]'' strains have also been successfully engineered to produce butanol by modifying their [[protein metabolism|amino acid metabolism]].<ref name="butanol">{{Cite news |date=14 January 2008 |title=Biofuels aim higher |work=Biofuels, Bioproducts and Biorefining (BioFPR) |url=http://www.biofpr.com/details/feature/102347/Biofuels_aim_higher.html |url-status=live |access-date=3 December 2008 |archive-url=https://web.archive.org/web/20090810045124/http://www.biofpr.com/details/feature/102347/Biofuels_aim_higher.html |archive-date=10 August 2009 |vauthors=Evans J}}</ref> One drawback to butanol production in ''E.&nbsp;coli'' remains the high cost of [[Growth medium|nutrient rich media]], however, recent work has demonstrated ''E.&nbsp;coli'' can produce butanol with minimal nutritional supplementation.<ref>{{cite journal |vauthors=Pontrelli S, Fricke RC, Sakurai SS, Putri SP, Fitz-Gibbon S, Chung M, Wu HY, Chen YJ, Pellegrini M, Fukusaki E, Liao JC |date=September 2018 |title=Directed strain evolution restructures metabolism for 1-butanol production in minimal media |journal=Metabolic Engineering |volume=49 |pages=153–163 |doi=10.1016/j.ymben.2018.08.004 |pmid=30107263 |doi-access=free}}</ref> Biobutanol is sometimes called [[biogasoline]], which is incorrect as it is chemically different, being an alcohol and not a hydrocarbon like gasoline.

==== Biodiesel ====
[[File:Biofuel pumps DCA 07 2010 9834.JPG|thumb|upright=1.2|Biofuel pumps, 2010]]
{{Main|Biodiesel}}

{{Further|Biodiesel around the world}}

Biodiesel 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. Chemically, it consists mostly of fatty acid methyl (or ethyl) esters ([[Fatty acid methyl ester|FAMEs]]).<ref>{{cite journal |vauthors=Fukuda H, Kondo A, Noda H |date=January 2001 |title=Biodiesel fuel production by transesterification of oils |journal=Journal of Bioscience and Bioengineering |volume=92 |issue=5 |pages=405–416 |doi=10.1016/s1389-1723(01)80288-7 |pmid=16233120}}</ref> Feedstocks for biodiesel include animal fats, vegetable oils, [[soy]], [[rapeseed]], [[Jatropha curcas|jatropha]], [[Madhuca longifolia|mahua]], [[mustard plant|mustard]], [[flax]], [[sunflower]], [[palm oil]], [[hemp]], [[thlaspi arvense|field pennycress]], ''[[Pongamia pinnata]]'' and [[algae fuel|algae]]. Pure biodiesel (B100, also known as "neat" biodiesel) currently reduces emissions with up to 60% compared to diesel Second generation B100.<ref>{{Cite web |title=Perstop Press release: Verdis Polaris Aura – second generation B100 – The advanced green one |url=https://www.perstorp.com/en/Media/Pressreleases/2013/20130701_Verdis_Polaris_Aura_second_generation_B100/ |archive-url=https://web.archive.org/web/20140804182248/https://www.perstorp.com/en/Media/Pressreleases/2013/20130701_Verdis_Polaris_Aura_second_generation_B100/ |archive-date=4 August 2014 |access-date=21 June 2014}}</ref> {{as of|2020}}, researchers at Australia's [[CSIRO]] have been studying [[safflower]] oil as an engine [[lubricant]], and researchers at [[Montana State University]]'s Advanced Fuels Center in the US have been studying the oil's performance in a large [[diesel engine]], with results described as a "breakthrough".<ref>{{cite web |date=7 June 2020 |title=Safflower oil hailed by scientists as possible recyclable, biodegradable replacement for petroleum |url=https://www.abc.net.au/news/2020-06-07/safflower-oil-new-biofuel-to-replace-petroleum/12321028 |url-status=live |archive-url=https://web.archive.org/web/20200607012058/https://www.abc.net.au/news/2020-06-07/safflower-oil-new-biofuel-to-replace-petroleum/12321028 |archive-date=7 June 2020 |access-date=7 June 2020 |website=ABC News |series=Landline |publisher=Australian Broadcasting Corporation |vauthors=Lee T}}</ref>

[[File:Targray Biodiesel Railcar.png|thumb|upright=1.2|Targray Biofuels Division railcar transporting Biodiesel.]]Biodiesel can be used in any diesel engine and modified equipment when mixed with mineral diesel. It can also be used in its pure form (B100) in diesel engines, but some maintenance and performance problems may occur during wintertime utilization, since the fuel becomes somewhat more [[viscosity|viscous]] at lower temperatures, depending on the feedstock used.<ref>{{Cite web |title=Alternative Fuels Data Center: Biodiesel Blends |url=https://afdc.energy.gov/fuels/biodiesel_blends.html |access-date=2022-03-31 |website=afdc.energy.gov}}</ref>

Electronically controlled '[[common rail]]' and '[[Unit Injector]]' type systems from the late 1990s onwards can only use biodiesel blended with conventional diesel fuel. These engines have finely metered and atomized multiple-stage injection systems that are very sensitive to the viscosity of the fuel. Many current-generation diesel engines are designed to run on B100 without altering the engine itself, although this depends on the [[fuel rail]] design. Since biodiesel is an effective [[solvent]] and cleans residues deposited by mineral diesel, [[oil filter|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.

Biodiesel is an [[oxygenate]]d fuel, meaning it contains a reduced amount of carbon and higher hydrogen and oxygen content than fossil diesel. This improves the [[combustion]] of biodiesel and reduces the particulate emissions from unburnt carbon. However, using pure biodiesel may increase NO<sub>x</sub>-emissions<ref>{{cite report |url=http://www.vtt.fi/inf/pdf/technology/2012/T46.pdf |title=Fuel and Technology Alternatives for Buses. Overall Energy Efficiency and Emission Performance. IEA Bioenergy Task 46 |date=2012 |publisher=VTT Technical Research Centre of Finland |archive-url=https://web.archive.org/web/20200216193457/https://www.vtt.fi/inf/pdf/technology/2012/T46.pdf |archive-date=16 February 2020 |vauthors=Nylund NO, Koponen K}}. Possibly the new emission standards Euro VI/EPA 10 will lead to reduced NO<sub>x</sub>-levels also when using B100.</ref> Biodiesel is also safe to handle and transport because it is non-toxic and [[biodegradable]], and has a high [[flash point]] of about 300&nbsp;°F (148&nbsp;°C) compared to petroleum diesel fuel, which has a flash point of 125&nbsp;°F (52&nbsp;°C).<ref>{{cite web |title=Biofuels Facts |url=http://www.hempcar.org/biofacts.shtml |archive-url=https://web.archive.org/web/20110520231032/http://hempcar.org/biofacts.shtml |archive-date=20 May 2011 |access-date=14 July 2010 |publisher=Hempcar.org}}</ref>

In many European countries, a 5% biodiesel blend is widely used and is available at thousands of gas stations.<ref>{{cite web |title=ADM Biodiesel: Hamburg, Leer, Mainz |url=http://www.biodiesel.de/ |url-status=live |archive-url=https://web.archive.org/web/20090802071245/http://www.biodiesel.de/ |archive-date=2 August 2009 |access-date=14 July 2010 |publisher=Biodiesel.de}}</ref><ref>{{cite web |author=RRI Limited for Biodiesel Filling Stations |title=Welcome to Biodiesel Filling Stations |url=http://www.biodieselfillingstations.co.uk |archive-url=https://web.archive.org/web/20180714031730/http://www.biodieselfillingstations.co.uk/ |archive-date=14 July 2018 |access-date=14 July 2010 |publisher=Biodieselfillingstations.co.uk}}</ref> In France, biodiesel is incorporated at a rate of 8% in the fuel used by all French diesel vehicles.<ref name="RA29">{{Harvsp|Avril Group : Activity Report|2014|p=58}}</ref> [[Avril Group]] produces under the brand [[Diester]], a fifth of 11&nbsp;million tons of biodiesel consumed annually by the [[European Union]].<ref name="EurObserv'ER">{{Harvsp|EurObserv|2014|p=4}}</ref> It is the leading European producer of biodiesel.<ref name="RA29" />

====Green diesel====

{{Main|Biodiesel production}}

[[Hydrotreated vegetable oil|Green diesel]] can be produced from a combination of biochemical and thermochemical processes. Conventional green diesel is produced through hydroprocessing biological oil feedstocks, such as vegetable oils and animal fats.<ref>{{cite web |title=Fast Pyrolysis and Bio-Oil Upgrading |url=http://www.ascension-publishing.com/BIZ/HD50.pdf |url-status=live |archive-url=https://web.archive.org/web/20120105183213/http://www.ascension-publishing.com/BIZ/HD50.pdf |archive-date=5 January 2012 |access-date=15 March 2012 |vauthors=Brown R, Holmgren J}}</ref><ref name="seven">{{cite web |title=Alternative & Advanced Fuels |url=http://www.afdc.energy.gov/fuels/emerging_green.html |url-status=live |archive-url=https://web.archive.org/web/20121027183202/http://www.afdc.energy.gov/fuels/emerging_green.html |archive-date=27 October 2012 |access-date=7 March 2012 |publisher=US Department of Energy}}</ref> Recently, it is produced using series of thermochemical processes such as pyrolysis and hydroprocessing. In the thermochemical route, syngas produced from gasification, bio-oil produced from pyrolysis or biocrude produced from hydrothermal liquefaction is upgraded to green diesel using hydroprocessing.<ref name=":2">{{Cite web |title=Technology {{!}} Comsyn |url=https://www.comsynproject.eu/technology/ |access-date=2024-04-19 |website=www.comsynproject.eu}}</ref><ref name=":3">{{Cite journal |last1=Lilonfe |first1=Sylvanus |last2=Dimitriou |first2=Ioanna |last3=Davies |first3=Ben |last4=Abdul-Manan |first4=Amir F. N. |last5=McKechnie |first5=Jon |date=2024-01-01 |title=Comparative techno-economic and life cycle analyses of synthetic "drop-in" fuel production from UK wet biomass |journal=Chemical Engineering Journal |volume=479 |article-number=147516 |doi=10.1016/j.cej.2023.147516 |doi-access=free |bibcode=2024ChEnJ.47947516L }}</ref><ref name=":4">{{Cite journal |last1=Lilonfe |first1=Sylvanus |last2=Davies |first2=Ben |last3=Abdul-Manan |first3=Amir F. N. |last4=Dimitriou |first4=Ioanna |last5=McKechnie |first5=Jon |date=2024-04-17 |title=A review of techno-economic analyses and life cycle greenhouse gas emissions of biomass-to-hydrocarbon "drop-in" fuels |journal=Sustainable Production and Consumption |volume=47 |pages=425–444 |doi=10.1016/j.spc.2024.04.016 |doi-access=free |bibcode=2024SusPC..47..425L }}</ref> Hydroprocessing is the process of using hydrogen to reform a molecular structure. For example, [[hydrocracking]] which is a widely used hydroprocessing technique in refineries is used at elevated temperatures and pressure in the presence of a catalyst to break down larger [[molecules]], such as those found in [[vegetable oil]]s, into shorter [[hydrocarbon]] chains used in [[diesel fuel|diesel]] engines.<ref name="alpha">{{cite journal |last1=Knothe |first1=Gerhard |title=Biodiesel and renewable diesel: A comparison |journal=Progress in Energy and Combustion Science |date=June 2010 |volume=36 |issue=3 |pages=364–373 |doi=10.1016/j.pecs.2009.11.004 |bibcode=2010PECS...36..364K }}</ref> Green diesel may also be called renewable diesel, drop-in biodiesel, hydrotreated vegetable oil (HVO fuel)<ref name="alpha" /> or hydrogen-derived renewable diesel.<ref name="seven" /> Unlike biodiesel, green diesel has exactly the same chemical properties as petroleum-based diesel.<ref name="alpha" /><ref>{{Cite web |title=Green Diesel v. Biodiesel |url=https://www.uop.com/processing-solutions/renewables/green-diesel/biodiesel/ |url-status=live |archive-url=https://web.archive.org/web/20180805143224/https://www.uop.com/processing-solutions/renewables/green-diesel/biodiesel/ |archive-date=5 August 2018 |access-date=5 August 2018}}</ref> It does not require new engines, pipelines or infrastructure to distribute and use, but has not been produced at a cost that is competitive with [[petroleum]].<ref name="seven" /> Gasoline versions are also being developed.<ref>{{cite news |title=Breakthroughs in Green Gasoline Production |newspaper=Biomass Magazine |url=http://biomassmagazine.com/articles/1731/breakthroughs-in-green-gasoline-production/ |url-status=live |access-date=14 August 2012 |archive-url=https://web.archive.org/web/20120311135648/http://biomassmagazine.com/articles/1731/breakthroughs-in-green-gasoline-production |archive-date=11 March 2012 |vauthors=Jessica E}}</ref> Green diesel is being developed in [[Louisiana]] and [[Singapore]] by [[ConocoPhillips]], [[Neste Oil]], [[Valero Energy Corporation|Valero]], Dynamic Fuels, and [[UOP LLC|Honeywell UOP]]<ref name="seven" /><ref>{{Cite report |url=http://www.pnnl.gov/main/publications/external/technical_reports/PNNL-20279.pdf |title=A Brief Literature Overview of Various Routes to Biorenewable Fuels from Lipids for the National Alliance of Advanced Biofuels and Bio-products NAAB Consortium |date=March 2011 |publisher=Prepared by the US Department of Energy |access-date=23 August 2012 |archive-url=https://web.archive.org/web/20120712170606/http://www.pnnl.gov/main/publications/external/technical_reports/PNNL-20279.pdf |archive-date=12 July 2012 |url-status=live |vauthors=Albrecht KO, Hallen RT |journal=}}</ref> as well as Preem in Gothenburg, Sweden, creating what is known as Evolution Diesel.<ref>{{cite web |date=August 2014 |title=Preem makes major investment in green diesel at the Port of Gothenburg – Port of Gothenburg |url=http://www.portofgothenburg.com/News-desk/Press-releases/Preem-makes-major-investment-in-green-diesel-at-the-Port-of-Gothenburg/ |archive-url=https://web.archive.org/web/20140801105736/http://www.portofgothenburg.com/News-desk/Press-releases/Preem-makes-major-investment-in-green-diesel-at-the-Port-of-Gothenburg/ |archive-date=1 August 2014}}</ref>

====Straight vegetable oil====
[[File:Walmart’s Grease Fuel Truck (2).jpg|thumb|upright=1.2|A biofuel truck in 2009<ref>{{cite web |date=3 February 2009 |title=Wal-Mart To Test Hybrid Trucks |url=https://www.sustainablebusiness.com/index.cfm/go/news.display/id/17599 |url-status=live |archive-url=https://web.archive.org/web/20140508095041/https://www.sustainablebusiness.com/index.cfm/go/news.display/id/17599 |archive-date=8 May 2014 |access-date=8 May 2014 |publisher=Sustainable Business}}</ref>]]
{{Main|Vegetable oil fuel}}

Straight unmodified [[Eating|edible]] vegetable oil is generally not used as fuel, but lower-quality oil has been used for this purpose. Used vegetable oil is increasingly being processed into biodiesel, or (more rarely) cleaned of water and particulates and then used as a fuel. The IEA estimates that biodiesel production used 17% of global vegetable oil supplies in 2021.<ref name="Renewables 2022 Biofuels" />

Oils and fats reacted with 10 pounds of a short-chain alcohol (usually methanol) in the presence of a catalyst (usually sodium hydroxide [NaOH] can be [[hydrogenated]] to give a diesel substitute.<ref>{{Cite web |title=Alternative Fuels Data Center: Biodiesel Production and Distribution |url=https://afdc.energy.gov/fuels/biodiesel_production.html#:~:text=Biodiesel%20is%20produced%20from%20vegetable,and%20glycerin%20(a%20coproduct). |access-date=2022-03-31 |website=afdc.energy.gov}}</ref> The resulting product is a straight-chain hydrocarbon with a high [[cetane number]], low in [[aromatics]] and [[sulfur]] and does not contain oxygen. [[Hydrogenated oil]]s can be blended with diesel in all proportions. They have several advantages over biodiesel, including good performance at low temperatures, no storage stability problems and no susceptibility to microbial attack.<ref name="evans">{{cite report |url=http://www.nnfcc.co.uk/metadot/index.pl?id=6597%3Bisa%3DDBRow%3Bop%3Dshow%3Bdbview_id%3D2457 |title=Liquid Transport Biofuels – Technology Status Report |date=14 April 2008 |publisher=[[National Non-Food Crops Centre]] |archive-url=https://web.archive.org/web/20080611062858/http://www.nnfcc.co.uk/metadot/index.pl?id=6597%3Bisa%3DDBRow%3Bop%3Dshow%3Bdbview_id%3D2457 |archive-date=11 June 2008 |vauthors=Evans G}}</ref>

==== Biogasoline ====
{{Main|Biogasoline}}

Biogasoline can be produced biologically and thermochemically. Using biological methods, a study led by Professor Lee Sang-yup at the Korea Advanced Institute of Science and Technology ([[KAIST]]) and published in the international science journal ''[[Nature (journal)|Nature]]'' used modified ''E.&nbsp;coli'' fed with glucose found in plants or other non-food crops to produce biogasoline with the produced enzymes. The enzymes converted the sugar into fatty acids and then turned these into hydrocarbons that were chemically and structurally identical to those found in commercial gasoline fuel.<ref name="fuels">{{cite report |url=https://www.fuelsandlubes.com/knowledge-base/south-korean-scientists-use-e-coli-to-make-gasoline/ |title=Liquid Transport Fuels&Lubes - South Korean scientists use E. coli to make gasoline |date=2013-11-04 |publisher=Fuels&Lubes Daily |archive-url=https://web.archive.org/web/20220907102013/https://www.fuelsandlubes.com/knowledge-base/south-korean-scientists-use-e-coli-to-make-gasoline/ |archive-date=2022-09-07}}</ref> The thermochemical approach of producing biogasoline are similar to those used to produce biodiesel.<ref name=":2" /><ref name=":3" /><ref name=":4" /> Biogasoline may also be called drop-in gasoline or renewable gasoline.

====Bioethers====
[[File:Sao Paulo ethanol pump 04 2008 74 zoom.jpg|thumb|upright=1.2|[[Common ethanol fuel mixtures#E100|Neat ethanol]] on the left&nbsp;(A), [[gasoline]] on the right (G) at a [[filling station]] in Brazil in 2008|alt=]]
Bioethers (also referred to as fuel [[ether]]s or oxygenated fuels) are cost-effective [[Chemical compound|compounds]] that act as [[octane rating]] enhancers. "Bioethers are produced by the reaction of reactive iso-olefins, such as iso-butylene, with bioethanol."<ref>{{cite web |year=2007 |title=Bioethers Impact on the Gasoline Pool |url=http://www.digitalrefining.com/article/1000210,Bioethers_impact_on_the_gasoline_pool.html |url-status=live |archive-url=https://web.archive.org/web/20161114001438/http://www.digitalrefining.com/article/1000210,Bioethers_impact_on_the_gasoline_pool.html |archive-date=14 November 2016 |access-date=15 February 2014 |publisher=Digital Refining |vauthors=Rock K, Korpelshoek M}}</ref>{{attribution needed|date=October 2022}} Bioethers are created from wheat or sugar beets, and also be produced from the waste glycerol that results from the production of biodiesel.<ref>{{Cite web |title=Biofuels - Types of Biofuels - Bioethers |url=http://biofuel.org.uk/bioethers.html |url-status=live |archive-url=https://web.archive.org/web/20160201004223/http://biofuel.org.uk/bioethers.html |archive-date=1 February 2016 |website=biofuel.org.uk}}</ref> They also enhance [[engine]] performance, while significantly reducing engine wear and [[toxic]] [[exhaust gas|exhaust emissions]]. By greatly reducing the amount of ground-level [[ozone]] emissions, they contribute to improved air quality.{{refn|{{CELEX|id=31985L0536|text=Council Directive 85/536/EEC of 5 December 1985 on crude-oil savings through the use of substitute fuel components in petrol}}. No longer in force, Date of end of validity: 31/12/1999; Repealed by 31998L0070.<ref>{{CELEX|id=01998L0070-20231120|text=Consolidated text: Directive 98/70/EC of the European Parliament and of the Council of 13 October 1998 relating to the quality of petrol and diesel fuels and amending Council Directive 93/12/EEC}}</ref>}}<ref>{{cite web |date=2007-01-31 |title=Impact Assessment of the Proposal for a Directive of the European Parliament and of the Council modifying Directive 98/70/EC relating to the quality of petrol and diesel fuels |url=http://www.europarl.europa.eu/registre/docs_autres_institutions/commission_europeenne/sec/2007/0055/COM_SEC(2007)0055_EN.pdf |url-status=live |archive-url=https://web.archive.org/web/20110715105028/http://www.europarl.europa.eu/registre/docs_autres_institutions/commission_europeenne/sec/2007/0055/COM_SEC(2007)0055_EN.pdf |archive-date=15 July 2011 |access-date=14 July 2010 |publisher=Commission of the European Communities |location=Brussels}}</ref>

In transportation fuel there are six ether additives: dimethyl ether (DME), [[diethyl ether]] (DEE), [[Methyl tert-butyl ether|methyl ''tert''-butyl ether]] (MTBE), [[Ethyl tert-butyl ether|ethyl ''tert''-butyl ether]] (ETBE), [[tert-Amyl methyl ether|''tert''-amyl methyl ether]] (TAME), and [[tert-Amyl ethyl ether|''tert''-amyl ethyl ether]] (TAEE).<ref>{{cite web |title=Bio-Ethers as Transportation Fuel: A Review |url=http://www.ascension-publishing.com/BIZ/DMEoverview.pdf |url-status=live |archive-url=https://web.archive.org/web/20111014172515/http://www.ascension-publishing.com/BIZ/DMEoverview.pdf |archive-date=14 October 2011 |access-date=15 February 2014 |publisher=Indian Institute of Petroleum Dehradun |vauthors=Sukla MK, Bhaskar T, Jain AK, Singal SK, Garg MO}}</ref>

The European Fuel Oxygenates Association identifies MTBE and ETBE as the most commonly used ethers in fuel to replace lead. Ethers were introduced in Europe in the 1970s to replace the highly toxic compound.<ref>{{cite web |title=What are Bio-Ethers? |url=http://www.petrochemistry.eu/ftp/pressroom/EFOA_2008_def.pdf |archive-url=https://web.archive.org/web/20140306082952/http://www.petrochemistry.eu/ftp/pressroom/EFOA_2008_def.pdf |archive-date=6 March 2014 |publisher=. The European Fuel Oxygenates Association}}</ref> Although Europeans still use bioether additives, the U.S. [[Energy Policy Act of 2005]] lifted a requirement for [[reformulated gasoline]] to include an oxygenate, leading to less MTBE being added to fuel.<ref>{{cite web |title=Gasoline |url=http://www.epa.gov/mtbe/gas.htm |archive-url=https://web.archive.org/web/20131206222912/http://www.epa.gov/mtbe/gas.htm |archive-date=6 December 2013 |access-date=6 March 2014 |publisher=Environmental Protection Agency}}</ref> Although bioethers are likely to replace ethers produced from petroleum in the UK, it is highly unlikely they will become a fuel in and of itself due to the low energy density.<ref>{{cite web |title=Biofuels – Types of Biofuels – Bioethers |url=http://biofuel.org.uk/bioethers.html |url-status=live |archive-url=https://web.archive.org/web/20160201004223/http://biofuel.org.uk/bioethers.html |archive-date=1 February 2016 |access-date=30 May 2015}}</ref>

====Aviation biofuel====
{{excerpt|Aviation biofuel}}

=== Gaseous ===

====Biogas and biomethane====
[[File:Biogas.jpg|thumb|upright=1.2|Biogas plant in 2007]]
{{Main|Biogas}}

Biogas is a mixture composed primarily of [[methane]] and [[carbon dioxide]] produced by the process of [[anaerobic digestion]] of [[organic material]] by [[micro-organisms]]. Other trace components of this mixture includes water vapor, [[hydrogen sulfide]], siloxanes, hydrocarbons, ammonia, oxygen, carbon monoxide, and nitrogen.<ref>{{cite journal |last1=Ryckebosch |first1=E. |last2=Drouillon |first2=M. |last3=Vervaeren |first3=H. |title=Techniques for transformation of biogas to biomethane |journal=Biomass and Bioenergy |date=May 2011 |volume=35 |issue=5 |pages=1633–1645 |doi=10.1016/j.biombioe.2011.02.033 |bibcode=2011BmBe...35.1633R }}</ref><ref>{{Cite web|date=2008-10-04|publisher=National Non-Food Crops Centre |id= NNFCC 08-006 | title=A Detailed Economic Assessment of Anaerobic Digestion Technology and its Suitability to UK Farming and Waste Systems (Andersons)|url=http://www.nnfcc.co.uk/metadot/index.pl?id=7198;isa=DBRow;op=show;dbview_id=2457|access-date=2023-01-02|archive-url=https://web.archive.org/web/20081004232058/http://www.nnfcc.co.uk/metadot/index.pl?id=7198;isa=DBRow;op=show;dbview_id=2457 |archive-date=4 October 2008 }}</ref> It can be produced either from [[biodegradable waste]] materials or by the use of [[energy crop]]s fed into [[anaerobic digester]]s to supplement gas yields. The solid byproduct, [[digestate]], can be used as a biofuel or a fertilizer. When {{CO2}} and other impurities are removed from biogas, it is called [[biomethane]]. The {{CO2}} can also be combined with hydrogen in [[methanation]] to form more methane.

Biogas can be recovered from [[mechanical biological treatment]] waste processing systems. [[Landfill gas]], a less clean form of biogas, is produced in [[landfill]]s through naturally occurring anaerobic digestion. If it escapes into the atmosphere, it acts as a [[greenhouse gas]].

In Sweden, "[[waste-to-energy]]" power plants capture methane biogas from garbage and use it to power transport systems.<ref>{{Cite news |last=Yee |first=Amy |date=2018-09-21 |title=In Sweden, Trash Heats Homes, Powers Buses and Fuels Taxi Fleets |url=https://www.nytimes.com/2018/09/21/climate/sweden-garbage-used-for-fuel.html |access-date=2024-03-14 |work=The New York Times }}</ref> Farmers can produce biogas from cattle [[manure]] via anaerobic digesters.<ref>"BIOGAS: No bull, manure can power your farm." Farmers Guardian (25 September 2009): 12. General OneFile. Gale.</ref>

==== Syngas ====

{{Main|Gasification}}

[[Syngas]], a mixture of [[carbon monoxide]], [[hydrogen]] and various hydrocarbons, is produced by partial combustion of biomass (combustion with an amount of [[oxygen]] that is not sufficient to convert the biomass completely to carbon dioxide and water).<ref name="evans" /> Before partial combustion the biomass is dried and sometimes [[pyrolysis|pyrolysed]]. 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, [[turbines]] or high-temperature fuel cells.<ref name="e-collection.ethbib.ethz.ch">{{cite thesis | url = http://e-collection.ethbib.ethz.ch/view/eth:41553 | title = Electricity from wood through the combination of gasification and solid oxide fuel cells | archive-url = https://web.archive.org/web/20110313035637/http://e-collection.ethbib.ethz.ch/view/eth:41553 | archive-date=13 March 2011 | degree = PhD | vauthors = Nagel F | publisher = Swiss Federal Institute of Technology Zurich | date = 2008 }}</ref> The [[wood gas generator]], a wood-fueled gasification reactor, can be connected to an internal combustion engine.

Syngas can be used to produce [[methanol]], [[dimethyl ether]] and [[hydrogen]], or converted via the [[Fischer–Tropsch process]] to produce a diesel substitute, or a mixture of alcohols that can be blended into gasoline. Gasification normally relies on temperatures greater than 700&nbsp;°C.

Lower-temperature gasification is desirable when co-producing [[biochar]], but results in syngas polluted with [[tar]].

=== Solid ===
{{Main|Solid fuel#Biomass}}
The term "biofuels" is also used for [[solid fuel]]s that are made from biomass, even though this is less common.<ref name="www.eia.gov-2023" />

== Research into other types ==

=== Algae-based biofuels ===
{{Main|Algaculture|Algae fuel}}

Algae can be produced in ponds or tanks on land, and out at sea.<ref name="Thomas-2020">{{cite web |title=Biofuel from Algae: The Pros and Cons of Pond Scum |url=https://www.thomasnet.com/insights/biofuel-from-algae-the-pros-and-cons-of-pond-scum/ |url-status=live |archive-url=https://web.archive.org/web/20200406004138/https://www.thomasnet.com/insights/biofuel-from-algae-the-pros-and-cons-of-pond-scum/ |archive-date=6 April 2020 |access-date=2020-10-25 |website=Thomasnet®|date=29 January 2020 }}</ref><ref name="Renewable Energy Magazine, at the heart of clean energy journalism 2020">{{cite web |date=2020-09-14 |title=Biomass - Offshore wind farms = seaweed = biofuel |url=https://www.renewableenergymagazine.com/biomass/offshore-wind-farms--seaweed--biofuel |url-status=live |archive-url=https://web.archive.org/web/20200727005336/https://www.renewableenergymagazine.com/biomass/offshore-wind-farms--seaweed--biofuel |archive-date=27 July 2020 |access-date=2020-10-16 |website=Renewable Energy Magazine, at the heart of clean energy journalism}}</ref> Algal fuels have high yields,<ref>{{cite journal |vauthors=Greenwell HC, Laurens LM, Shields RJ, Lovitt RW, Flynn KJ |date=May 2010 |title=Placing microalgae on the biofuels priority list: a review of the technological challenges |journal=Journal of the Royal Society, Interface |volume=7 |issue=46 |pages=703–726 |doi=10.1098/rsif.2009.0322 |pmc=2874236 |pmid=20031983}}</ref> a high [[Flash point|ignition point]],<ref>{{Cite journal |vauthors=Dinh LT, Guo Y, Mannan MS |year=2009 |title=Sustainability evaluation of biodiesel production using multicriteria decision-making |journal=Environmental Progress & Sustainable Energy |volume=28 |issue=1 |pages=38–46 |bibcode=2009EPSE...28...38D |doi=10.1002/ep.10335 }}</ref> can be grown with minimal impact on [[fresh water]] resources,<ref>{{cite journal |last1=Ajayebi |first1=Atta |last2=Gnansounou |first2=Edgard |last3=Kenthorai Raman |first3=Jegannathan |title=Comparative life cycle assessment of biodiesel from algae and jatropha: A case study of India |journal=Bioresource Technology |date=December 2013 |volume=150 |pages=429–437 |doi=10.1016/j.biortech.2013.09.118 |pmid=24140355 |bibcode=2013BiTec.150..429A |url=http://infoscience.epfl.ch/record/199154 }}</ref><ref>{{cite journal |last1=Yang |first1=Jia |last2=Xu |first2=Ming |last3=Zhang |first3=Xuezhi |last4=Hu |first4=Qiang |last5=Sommerfeld |first5=Milton |last6=Chen |first6=Yongsheng |title=Life-cycle analysis on biodiesel production from microalgae: Water footprint and nutrients balance |journal=Bioresource Technology |date=January 2011 |volume=102 |issue=1 |pages=159–165 |doi=10.1016/j.biortech.2010.07.017 |pmid=20675125 |bibcode=2011BiTec.102..159Y }}</ref><ref name="gas2.0">{{cite web |date=29 March 2008 |title=First Algae Biodiesel Plant Goes Online: 1 April 2008 |url=http://gas2.org/2008/03/29/first-algae-biodiesel-plant-goes-online-april-1-2008/ |url-status=live |archive-url=https://web.archive.org/web/20190618110905/https://gas2.org/2008/03/29/first-algae-biodiesel-plant-goes-online-april-1-2008/ |archive-date=18 June 2019 |access-date=10 June 2008 |publisher=Gas 2.0 |vauthors=Cornell CB}}</ref> can be produced using saline water and [[wastewater]], and are [[biodegradable]] and relatively harmless to the environment if spilled.<ref>{{Cite journal |vauthors=Demirbas AH |year=2011 |title=Biodiesel from oilgae, biofixation of carbon dioxide by microalgae: A solution to pollution problems |journal=Applied Energy |volume=88 |issue=10 |pages=3541–3547 |doi=10.1016/j.apenergy.2010.12.050 |bibcode=2011ApEn...88.3541D |hdl=11503/1330}}</ref><ref>{{cite journal |vauthors=Demirbas AH |year=2009 |title=Inexpensive oil and fats feedstocks for production of biodiesel |journal=Energy Education Science and Technology Part A: Energy Science and Research |volume=23 |pages=1–13}}</ref>  However, production requires large amounts of energy and fertilizer, the produced fuel degrades faster than other biofuels, and it does not flow well in cold temperatures.<ref name="Thomas-2020" /><ref>{{cite journal |last1=Rodionova |first1=M.V. |last2=Poudyal |first2=R.S. |last3=Tiwari |first3=I. |last4=Voloshin |first4=R.A. |last5=Zharmukhamedov |first5=S.K. |last6=Nam |first6=H.G. |last7=Zayadan |first7=B.K. |last8=Bruce |first8=B.D. |last9=Hou |first9=H.J.M. |last10=Allakhverdiev |first10=S.I. |title=Biofuel production: Challenges and opportunities |journal=International Journal of Hydrogen Energy |date=March 2017 |volume=42 |issue=12 |pages=8450–8461 |doi=10.1016/j.ijhydene.2016.11.125 |bibcode=2017IJHE...42.8450R }}</ref>

By 2017, due to economic considerations, most efforts to produce fuel from algae have been abandoned or changed to other applications.<ref name="Eric Wesoff">{{cite web |date=19 April 2017 |title=Hard Lessons From the Great Algae Biofuel Bubble |url=https://www.greentechmedia.com/articles/read/lessons-from-the-great-algae-biofuel-bubble |url-status=live |archive-url=https://web.archive.org/web/20170705164003/https://www.greentechmedia.com/articles/read/lessons-from-the-great-algae-biofuel-bubble |archive-date=5 July 2017 |access-date=5 August 2017 |vauthors=Wesoff E}}</ref>

Third and fourth-generation biofuels also include biofuels that are produced by bioengineered organisms i.e. algae and cyanobacteria.<ref name="Aro-2016">{{cite journal |vauthors=Aro EM |date=January 2016 |title=From first generation biofuels to advanced solar biofuels |journal=Ambio |volume=45 |issue=Supplement 1 |pages=S24–S31 |doi=10.1007/s13280-015-0730-0 |pmc=4678123 |pmid=26667057|bibcode=2016Ambio..45S..24A }}</ref> Algae and cyanobacteria will use water, carbon dioxide, and solar energy to produce biofuels.<ref name="Aro-2016" /> This method of biofuel production is still at the research level. The biofuels that are secreted by the bioengineered organisms are expected to have higher photon-to-fuel conversion efficiency, compared to older generations of biofuels.<ref name="Aro-2016" /> One of the advantages of this class of biofuels is that the cultivation of the organisms that produce the biofuels does not require the use of arable land.<ref name="Abdullah-2019">{{Cite journal |vauthors=Abdullah B, Muhammad SA, Shokravi Z, Ismail S, Kassim KA, Mahmood AN, Aziz MM |date=June 2019 |title=Fourth generation biofuel: A review on risks and mitigation strategies |journal=Renewable and Sustainable Energy Reviews |language=en |volume=107 |pages=37–50 |doi=10.1016/j.rser.2019.02.018 |bibcode=2019RSERv.107...37A }}</ref> The disadvantages include the cost of cultivating the biofuel-producing organisms being very high.<ref name="Abdullah-2019" />

Recent research highlights that the transition to sustainable energy is reliant on the widespread adoption of third- and fourth-generation biofuels, which utilize non-food sources such as algae and incorporate advanced processes like artificial photosynthesis. These alternatives are essential for climate change mitigation because they significantly reduce the land-use competition and sustainability risks associated with earlier biofuel generations.<ref>{{cite journal |last1=Rial |first1=Rafael Cardoso |title=Biofuels versus climate change: Exploring potentials and challenges in the energy transition |journal=Renewable and Sustainable Energy Reviews |date=May 2024 |volume=196 |article-number=114369 |doi=10.1016/j.rser.2024.114369 |bibcode=2024RSERv.19614369R }}</ref>

=== Electrofuels and solar fuels ===
[[Electrofuel]]s{{Citation needed|date=May 2022}} and [[solar fuel]]s may or may not be biofuels, depending on whether they contain biological elements. [[Electrofuel]]s are made by storing [[electrical energy]] in the chemical bonds of liquids and gases. The primary targets are [[butanol]], biodiesel, and [[Hydrogen fuel|hydrogen]], but include other alcohols and carbon-containing gases such as [[methane]] and [[butane]]. A solar fuel is a synthetic chemical [[fuel]] produced from solar energy. Light is converted to [[chemical energy]], typically by reducing [[protons]] to [[hydrogen]], or [[carbon dioxide]] to [[organic compounds]].<ref>{{Cite journal |vauthors=Lü J, Sheahan C, Fu P |date=2011 |title=Metabolic engineering of algae for fourth generation biofuels production |journal=Energy & Environmental Science |volume=4 |issue=7 |page=2451 |doi=10.1039/c0ee00593b |bibcode=2011EnEnS...4.2451L }}</ref>

== Bio-digesters ==
A bio-digester is a mechanized toilet that uses decomposition and sedimentation to turn human waste into a renewable fuel called biogas. Biogas can be made from substances like agricultural waste and sewage.<ref>{{Cite journal |last1=Xu |first1=Fuqing |last2=Li |first2=Yangyang |last3=Ge |first3=Xumeng |last4=Yang |first4=Liangcheng |last5=Li |first5=Yebo |date=2018-01-01 |title=Anaerobic digestion of food waste – Challenges and opportunities |journal=Bioresource Technology |volume=247 |pages=1047–1058 |doi=10.1016/j.biortech.2017.09.020 |pmid=28965912 |doi-access=free |bibcode=2018BiTec.247.1047X }}</ref><ref>{{cite journal |last1=Mahmudul |first1=H.M. |last2=Rasul |first2=M.G. |last3=Akbar |first3=D. |last4=Narayanan |first4=R. |last5=Mofijur |first5=M. |title=A comprehensive review of the recent development and challenges of a solar-assisted biodigester system |journal=Science of the Total Environment |date=January 2021 |volume=753 |article-number=141920 |doi=10.1016/j.scitotenv.2020.141920 |pmid=32889316 |bibcode=2021ScTEn.75341920M }}</ref> The bio-digester uses a process called anaerobic digestion to produce biogas. Anaerobic digestion uses a chemical process to break down organic matter with the use of microorganisms in the absence of oxygen to produce biogas.<ref>{{cite journal |last1=Kougias |first1=Panagiotis G. |last2=Angelidaki |first2=Irini |title=Biogas and its opportunities—A review |journal=Frontiers of Environmental Science & Engineering |date=June 2018 |volume=12 |issue=3 |article-number=14 |doi=10.1007/s11783-018-1037-8 |bibcode=2018FrESE..12...14K }}</ref> The processes involved in anaerobic respiration are hydrolysis, [[acidogenesis]], [[acetogenesis]], and [[methanogenesis]].<ref>{{cite journal |last1=Zhang |first1=Cunsheng |last2=Su |first2=Haijia |last3=Baeyens |first3=Jan |last4=Tan |first4=Tianwei |title=Reviewing the anaerobic digestion of food waste for biogas production |journal=Renewable and Sustainable Energy Reviews |date=October 2014 |volume=38 |pages=383–392 |doi=10.1016/j.rser.2014.05.038 |bibcode=2014RSERv..38..383Z }}</ref>

== Extent of production and use ==
<!-- Deleted image removed: [[File:Biofuel energy production.png|thumb|upright=1.6|Biofuel energy production, 2024<ref>{{cite web |title=Biofuel energy production |url=https://ourworldindata.org/grapher/biofuel-production |website=Our World in Data |access-date=27 June 2025}}</ref>]] -->
[[File:Biofuel production by region, OWID.svg|thumb|upright=1.6|Biofuel production by region]]
Global biofuel production was 81 [[Million Tonnes of Oil Equivalent|Mtoe]] in 2017 which represented an annual increase of about 3% compared to 2010.<ref name="Letcher chapter 1">{{Cite book |title=Future energy: improved, sustainable and clean options for our planet |date=2020 |editor=T. M. Letcher |isbn=978-0-08-102887-2 |edition=3rd |location=Amsterdam, Netherlands |chapter=Chapter1: Introduction With a Focus on Atmospheric Carbon Dioxide and Climate Change |oclc=1137604985}}</ref>{{rp|12}} In 2017, the US was the largest biofuel producer in the world producing 37 Mtoe, followed by Brazil and South America at 23 Mtoe and Europe (mainly Germany) at 12 Mtoe.<ref name="Letcher chapter 1" />{{rp|12}}

An assessment from 2017 found that: "Biofuels will never be a major transport fuel as there is just not enough land in the world to grow plants to make biofuel for all vehicles. It can however, be part of an energy mix to take us into a future of [[renewable energy]]."<ref name="Letcher chapter 1" />{{rp|11}}

In 2021, worldwide biofuel production provided 4.3% of the world's fuels for transport, including a very small amount of [[aviation biofuel]].<ref name="IEA-2022">{{Cite web |title=Transport biofuels – Renewables 2022 – Analysis |url=https://www.iea.org/reports/renewables-2022/transport-biofuels |access-date=2023-01-30 |website=IEA |language=en-GB}}</ref> By 2027, worldwide biofuel production is expected to supply 5.4% of the world's fuels for transport including 1% of aviation fuel.<ref name="IEA-2022" />

The US, Europe, Brazil and Indonesia are driving the majority of biofuel consumption growth. This demand for biodiesel, renewable diesel and biojet fuel is projected to increase by 44% (21 billion litres) over 2022-2027.<ref>{{Cite web |title=Is the biofuel industry approaching a feedstock crunch? – Analysis |url=https://www.iea.org/reports/is-the-biofuel-industry-approaching-a-feedstock-crunch |access-date=2024-03-13 |website=IEA |date=6 December 2022 |language=en-GB}}</ref>

== Issues ==
[[File:Wheat harvest.jpg|thumb|upright=1.2|Wheat fields in the USA: wheat is grown for food but also for biofuel production.]]
{{excerpt|Issues relating to biofuels}}

=== Environmental impacts ===
{{Further|Sustainable biofuels}}
[[File:Deforestation near Bukit Tiga Puluh NP.jpg|thumb|220px|[[Deforestation in Indonesia]], to make way for an [[oil palm]] plantation.<ref>{{cite news |title=Indonesia's biodiesel drive is leading to deforestation |url=https://www.bbc.com/news/59387191 |work=BBC News |date=8 December 2021}}</ref>]]
Estimates about the climate impact from biofuels vary widely based on the methodology and exact situation examined.<ref name="Jeswani-2020">{{cite journal |vauthors=Jeswani HK, Chilvers A, Azapagic A |date=November 2020 |title=Environmental sustainability of biofuels: a review |journal= Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences|volume=476 |issue=2243 |article-number=20200351 |bibcode=2020RSPSA.47600351J |doi=10.1098/rspa.2020.0351 |pmc=7735313 |pmid=33363439}}</ref>

In general, biofuels emit fewer [[greenhouse gas emissions]] when burned in an engine and are generally considered [[carbon-neutral fuel]]s as the carbon they emit has been [[Carbon sequestration|captured]] from the atmosphere by the crops used in biofuel production.<ref name="Lewandrowski Rosenfeld Pape Hendrickson pp. 361–375">{{cite journal |vauthors=Lewandrowski J, Rosenfeld J, Pape D, Hendrickson T, Jaglo K, Moffroid K |date=2019-03-25 |title=The greenhouse gas benefits of corn ethanol – assessing recent evidence |journal=Biofuels |publisher=Informa UK Limited |volume=11 |issue=3 |pages=361–375 |doi=10.1080/17597269.2018.1546488 |doi-access=free }}</ref> They can have greenhouse gas emissions ranging from as low as -127.1 gCO<sub>2</sub>eq per MJ when carbon capture is incorporated into their production to those exceeding 95 gCO<sub>2</sub>eq per MJ when [[land-use change]] is significant.<ref name=":3" /><ref name=":4" /> Several factors are responsible for the variation in emission numbers of biofuel, such as feedstock and its origin, fuel production technique, system boundary definitions, and energy sources.<ref name=":4" /> However, many government policies, such as those by the European Union and the UK, require that biofuels have at least 65% greenhouse gas emissions savings (or 70% if it is renewable fuels of non-biological origins) relative to fossil fuels.<ref>{{Cite web |title=Press corner |url=https://ec.europa.eu/commission/presscorner/home/en |access-date=2024-04-19 |website=European Commission - European Commission}}</ref><ref>{{Cite web |title=Biomass Strategy 2023 |url=https://www.gov.uk/government/publications/biomass-strategy |access-date=2024-04-19 |website=GOV.UK |language=en}}</ref>

The growing demand for biofuels has raised concerns about land use and food security. Many biofuel crops are grown on land that could otherwise be used for food production. This shift in land use can lead to several problems:

* '''Competition with Food Crops''': The cultivation of biofuels, especially in food-insecure regions, can drive up the cost of food and reduce the amount of land available for growing essential crops. This can exacerbate global food insecurity, especially in developing countries.
** '''Deforestation and Habitat Loss''': To meet the increasing demand for biofuels, large areas of forests and natural habitats are being cleared for agriculture. This deforestation leads to the loss of biodiversity, threatens wildlife species, and disrupts ecosystems.

=== Biodiversity Loss ===
The expansion of biofuel production, particularly through monoculture farming (growing a single crop on a large scale), poses a significant threat to biodiversity. Large-scale biofuel crop production can lead to:

* '''Habitat Destruction''': The conversion of natural ecosystems into agricultural land can result in the loss of habitats for many plant and animal species, leading to decreased biodiversity.
* '''Soil Degradation''': Monoculture farming can deplete soil nutrients, reduce soil fertility, and increase the need for chemical inputs like fertilizers and pesticides, which can further harm surrounding ecosystems
** '''Soil Fertility''': Continuous cultivation of biofuel crops without proper crop rotation or sustainable farming practices can lead to soil depletion. Over time, the soil may lose vital nutrients, making it less suitable for farming.

[[Life-cycle assessment]]s of first-generation biofuels have shown large emissions associated with the potential [[land-use change]] required to produce additional biofuel feedstocks.<ref name="Jeswani-2020" /><ref name="Lark Hendricks Smith Pates 2022 p.">{{cite journal |vauthors=Lark TJ, Hendricks NP, Smith A, Pates N, Spawn-Lee SA, Bougie M, Booth EG, Kucharik CJ, Gibbs HK |date=March 2022 |title=Environmental outcomes of the US Renewable Fuel Standard |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=119 |issue=9 |article-number=e2101084119 |bibcode=2022PNAS..11901084L |doi=10.1073/pnas.2101084119 |doi-access=free |pmc=8892349 |pmid=35165202}}</ref> If no land-use change is involved, first-generation biofuels can—on average—have lower emissions than fossil fuels.<ref name="Jeswani-2020" /> However, biofuel production can compete with food crop production. Up to 40% of corn produced in the United States is used to make ethanol<ref>{{cite news |last1=Terazono |first1=Emiko |last2=Hodgson |first2=Camilla |title=Food vs fuel: Ukraine war sharpens debate on use of crops for energy |url=https://www.ft.com/content/b424067e-f56b-4e49-ac34-5b3de07e7f08 |work=Financial Times |date=12 June 2022 }}</ref> and worldwide 10% of all grain is turned into biofuel.<ref>{{cite news |date=6 June 2022 |title=Guest view: Global hunger fight means no biofuel |work=Reuters |url=https://www.reuters.com/breakingviews/guest-view-global-hunger-fight-means-no-biofuel-2022-06-06/}}</ref> A 50% reduction in grain used for biofuels in the US and Europe would replace all of [[Ukraine]]'s grain exports.<ref>{{cite news |date=14 March 2022 |title=Cutting biofuels can help avoid global food shock from Ukraine war |work=New Scientist |url=https://www.newscientist.com/article/2312151-cutting-biofuels-can-help-avoid-global-food-shock-from-ukraine-war/}}</ref> Several studies have shown that reductions in emissions from biofuels are achieved at the expense of other impacts, such as [[Ocean acidification|acidification]], [[eutrophication]], [[water footprint]] and [[biodiversity loss]].<ref name="Jeswani-2020" />

Second-generation biofuels are thought to increase environmental sustainability since the non-food part of plants is being used to produce second-generation biofuels instead of being disposed of.<ref>{{Cite journal |vauthors=Antizar-Ladislao B, Turrion-Gomez JL |date=September 2008 |title=Second-generation biofuels and local bioenergy systems |journal=Biofuels, Bioproducts and Biorefining |language=en |volume=2 |issue=5 |pages=455–469 |doi=10.1002/bbb.97 |doi-access=free }}</ref>  But the use of second-generation biofuels increases the competition for lignocellulosic biomass, increasing the cost of these biofuels.<ref>{{Cite journal |vauthors=Bryngemark E |date=December 2019 |title=Second generation biofuels and the competition for forest raw materials: A partial equilibrium analysis of Sweden |journal=Forest Policy and Economics |volume=109 |article-number=102022 |doi=10.1016/j.forpol.2019.102022 |bibcode=2019ForPE.10902022B }}</ref>

In theory, third-generation biofuels, produced from algae, shouldn't harm the environment more than first- or second-generation biofuels due to lower changes in land use and the fact that they do not require pesticide use for production.<ref>{{Cite book |title=3rd generation biofuels: disruptive technologies to enable commercial production |date=2022 |publisher=Woodhead Publishing, an imprint of Elsevier |isbn=978-0-323-90971-6 |editor-last=Jacob-Lopes |editor-first=Eduardo |series=Woodhead Publishing series in energy |location=Cambridge, MA Kidlington |editor-last2=Zepka |editor-first2=Leila Queiroz |editor-last3=Severo |editor-first3=Ihana Aguiar |editor-last4=Maroneze |editor-first4=Mariana Manzoni}}</ref> When looking at the data however, it has been shown that the environmental cost to produce the infrastructure and energy required for third generation biofuel production, are higher than the benefits provided from the biofuels use.<ref>{{Cite web |last=Magazine |first=Hakai |title=Biofuel Made from Algae Isn't the Holy Grail We Expected |url=https://hakaimagazine.com/news/biofuel-made-from-algae-isnt-the-holy-grail-we-expected/ |access-date=2024-03-31 |website=Hakai Magazine |language=en}}</ref><ref>{{cite journal |last1=Rodionova |first1=M. V. |last2=Poudyal |first2=R. S. |last3=Tiwari |first3=I. |last4=Voloshin |first4=R. A. |last5=Zharmukhamedov |first5=S. K. |last6=Nam |first6=H. G. |last7=Zayadan |first7=B. K. |last8=Bruce |first8=B. D. |last9=Hou |first9=H. J. M. |last10=Allakhverdiev |first10=S. I. |title=Biofuel production: Challenges and opportunities |journal=International Journal of Hydrogen Energy |date=2017 |volume=42 |issue=12 |pages=8450–8461 |doi=10.1016/j.ijhydene.2016.11.125|bibcode=2017IJHE...42.8450R }}</ref>

The [[European Commission]] has officially approved a measure to phase out [[palm oil]]-based biofuels by 2030.<ref>{{cite news |title=Palm Oil Exporter Indonesia Concerned by EU's Deforestation Law |url=https://jakartaglobe.id/business/palm-oil-exporter-indonesia-concerned-by-eus-deforestation-law |work=Jakarta Globe |date=22 May 2022}}</ref><ref>{{cite news |title=EU palm oil use and imports seen plummeting by 2032 |url=https://www.reuters.com/markets/commodities/eu-palm-oil-use-imports-seen-plummeting-by-2032-2022-12-08/ |work=Reuters |date=8 December 2022}}</ref> Unsustainable palm oil agriculture has caused significant environmental and social problems, including deforestation and pollution.

The production of biofuels can be very energy intensive, which, if generated from non-renewable sources, can heavily mitigate the benefits gained through biofuel use. A solution proposed to solve this issue is to supply biofuel production facilities with excess nuclear energy, which can supplement the power provided by fossil fuels.<ref>{{cite journal |last1=Forsberg |first1=Charles |title=The Real Path to Green Energy: Hybrid Nuclear-Renewable Power |journal=Bulletin of the Atomic Scientists |date=January 2009 |volume=65 |issue=6 |pages=65–71 |doi=10.2968/065006007 |bibcode=2009BuAtS..65f..65F }}</ref> This can provide a carbon inexpensive solution to help reduce the environmental impacts of biofuel production.

===Indirect land use change impacts of biofuels===
{{excerpt|Indirect land use change impacts of biofuels}}

== See also ==
{{Portal|Renewable energy|Energy|Biology|Technology|Ecology}}
{{Div col}}
* [[Aviation biofuel]]
* [[Bioenergy Europe]]
* [[BioEthanol for Sustainable Transport]]
* [[Biofuels by region]]
* [[Biofuels Center of North Carolina]]
* [[Biogas powerplant]]
* [[International Renewable Energy Agency]]
* [[List of biofuel companies and researchers]]
* [[List of vegetable oils#Oils used for biofuel|List of vegetable oils used for biofuel]]
* [[Renewable energy by country]]
* [[Residue-to-product ratio]]
* [[Sustainable aviation fuel]]
* [[Sustainable transport]]
* [[Table of biofuel crop yields]]
{{div col end}}

== References ==
{{Reflist}}

===Sources===
* {{cite report|url=http://www.groupeavril.com/sites/default/files/annual-report-groupe-avril-2014-english.pdf|editor1-last=Avril Group|title=A new springtime for the oils and proteins sectors: Activity Report 2014|location=Paris|publisher=Avril|year=2015|page=65|ref={{sfnref|Avril Group : Activity Report|2014}}|access-date=11 August 2022|archive-date=26 October 2020|archive-url=https://web.archive.org/web/20201026043455/https://www.groupeavril.com/sites/default/files/annual-report-groupe-avril-2014-english.pdf}}
* {{Cite report|url =http://www.energies-renouvelables.org/observ-er/stat_baro/observ/baro222_en.pdf |title=Biofuel barometer|author=EurObserv|date=July 2014}}

== External links ==
{{wiktionary}}
* [http://www.future-science.com/loi/bfs Biofuels Journal]
* [http://www.eere.energy.gov/afdc/fuels/stations_locator.html Alternative Fueling Station Locator] {{Webarchive|url=https://web.archive.org/web/20080714060953/http://www.eere.energy.gov/afdc/fuels/stations_locator.html |date=14 July 2008 }} ([[EERE]])
* [https://web.archive.org/web/20091122133933/http://www.unep.fr/scp/rpanel/pdf/Assessing_Biofuels_Full_Report.pdf Towards Sustainable Production and Use of Resources: Assessing Biofuels] by the [[United Nations Environment Programme]], October 2009.
* [https://web.archive.org/web/20101229084204/http://www.netregs.gov.uk/netregs/94953.aspx Biofuels guidance for businesses, including permits and licences required] on [[NetRegs]].gov.uk
* [https://web.archive.org/web/20090210045405/http://www.spectrum.ieee.org/apr08/6182 How Much Water Does It Take to Make Electricity?]—Natural gas requires the least water to produce energy, some biofuels the most, according to a new study.
* [https://web.archive.org/web/20080214115435/http://ec.europa.eu/energy/res/events/biofuels.htm International Conference on Biofuels Standards] – European Union Biofuels Standardization
* [http://web.mit.edu/professional/short-programs/courses/biofuels_biomass.html Biofuels from Biomass: Technology and Policy Considerations] Thorough overview from MIT
* [https://www.theguardian.com/environment/biofuels The Guardian news on biofuels]
* [https://web.archive.org/web/20040515205329/http://www.eere.energy.gov/cleancities/ The US DOE Clean Cities Program] – links to the 87 US [[Clean Cities]] coalitions, as of 2004.
* [https://web.archive.org/web/20090419194948/http://css.snre.umich.edu/css_doc/CSS08-09.pdf Biofuels Factsheet] by the [[University of Michigan]]'s [http://css.snre.umich.edu/ Center for Sustainable Systems]
* [http://www.learnbiofuels.org/what-are-biofuels Learn Biofuels – Educational Resource for Students]

{{Bioenergy}}
{{Environmental technology}}
{{Global Warming|state=collapsed}}
{{Sustainability}}
{{emerging technologies|energy=yes}}
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{{DEFAULTSORT:Biofuel}}
[[Category:Biofuels| ]]
[[Category:Anaerobic digestion]]
[[Category:Biodegradable waste management]]
[[Category:Bioenergy]]
[[Category:Biomass]]
[[Category:Bright green environmentalism]]
[[Category:Economics and climate change]]
[[Category:Emissions reduction]]
[[Category:Fuels]]
[[Category:Renewable fuels]]
[[Category:Sustainable technologies]]