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A sample of biodiesel
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Renewable energy

Biofuel is a fuel that is produced over a short time span from biomass, rather than by the very slow natural processes involved in the formation of fossil fuels such as oil.[1] Biofuel can be produced from plants or from agricultural, domestic or industrial bio waste.[2][3][4][5] Biofuels are mostly used for transportation, but can also be used for heating and electricity.[6]: 173 [7] Biofuels (and bio energy in general) are regarded as a renewable energy source.[8]: 11  The use of biofuel has been subject to criticism regarding the "food vs fuel" debate, varied assessments of their sustainability, and ongoing deforestation and biodiversity loss as a result of biofuel production.[9]

In general, biofuels emit fewer greenhouse gas emissions when burned in an engine and are generally considered carbon-neutral fuels as the carbon emitted has been captured from the atmosphere by the crops used in production.[10] However, life-cycle assessments of biofuels have shown large emissions associated with the potential land-use change required to produce additional biofuel feedstocks.[11][12] 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.[13] Estimates about the climate impact from biofuels vary widely based on the methodology and exact situation examined.[11] 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.

Global demand for biofuels is predicted to increase by 56% over 2022–2027.[14] By 2027 worldwide biofuel production is expected to supply 5.4% of the world's fuels for transport including 1% of aviation fuel.[15] Demand for aviation biofuel is forecast to increase.[16][17] However some policy has been criticised for favoring ground transportation over aviation.[18]

The two most common types of biofuel are 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.[19]

Bioethanol is an alcohol made by fermentation, mostly from carbohydrates produced in sugar or starch crops such as maize, sugarcane, or sweet sorghum. 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 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 additive to reduce levels of particulates, carbon monoxide, and hydrocarbons from diesel-powered vehicles.[20]

Terminology

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See also: Biomass (energy) § Terminology
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."[6]: 173 

Other publications reserve the term biofuel for liquid or gaseous fuels, used for transportation.[7]

The IPCC Sixth Assessment Report defines biofuel as "A fuel, generally in liquid form, produced from biomass. Biofuels include bioethanol from sugarcane, sugar beet or maize, and biodiesel from canola or soybeans.".[21]: 1795  It goes on to define biomass in this context as "organic material excluding the material that is fossilised or embedded in geological formations".[21]: 1795  This means that coal or other fossil fuels is not a form of biomass in this context.

Conventional biofuels (first generation)

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First-generation biofuels (also denoted as "conventional biofuels") are made from food crops grown on arable land.[22][23]: 447  The crop's sugar, starch, or oil content is converted into biodiesel or ethanol, using transesterification, or yeast fermentation.[24]

Advanced biofuels

[edit]

To avoid a "food versus fuel" dilemma, second-generation biofuels and third-generation biofuels (also called advanced biofuels or sustainable biofuels 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.[25] 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.[23]: 448  [26]

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.[27]

Types

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Liquid

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Ethanol

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Main article: Ethanol fuel

Biologically produced alcohols, most commonly ethanol, and less commonly propanol and butanol, are produced by the action of microorganisms and enzymes through the fermentation of sugars or starches (easiest 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.[28]

Ethanol fuel is the most common biofuel worldwide, particularly in Brazil. Alcohol fuels are produced by fermentation of sugars derived from wheat, corn, sugar beets, sugar cane, molasses and any sugar or starch from which alcoholic beverages such as whiskey, can be made (such as potato and fruit waste, etc.). Production methods used are enzyme digestion (to release sugars from stored starches), fermentation of the sugars, distillation and drying. The distillation process requires significant energy input 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.[29]

Other biofuels

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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.[30] The methanol economy is an alternative to the hydrogen economy to be contrasted with today's hydrogen production from natural gas.

Butanol (C
4H
9OH) is formed by ABE fermentation (acetone, butanol, ethanol) and experimental modifications of the process show potentially high net energy gains 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),[31] 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 amino acid metabolism.[32] One drawback to butanol production in E. coli remains the high cost of nutrient rich media, however, recent work has demonstrated E. coli can produce butanol with minimal nutritional supplementation.[33] Biobutanol is sometimes called biogasoline, which is incorrect as it is chemically different, being an alcohol and not a hydrocarbon like gasoline.

Biodiesel

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Biofuel pumps, 2010
Main article: Biodiesel
Further information: 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 (FAMEs).[34] Feedstocks for biodiesel include animal fats, vegetable oils, soy, rapeseed, jatropha, mahua, mustard, flax, sunflower, palm oil, hemp, field pennycress, Pongamia pinnata and algae. Pure biodiesel (B100, also known as "neat" biodiesel) currently reduces emissions with up to 60% compared to diesel Second generation B100.[35] 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".[36]

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 viscous at lower temperatures, depending on the feedstock used.[37]

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, 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 oxygenated 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 NOx-emissions[38] Biodiesel is also safe to handle and transport because it is non-toxic and biodegradable, and has a high flash point of about 300 °F (148 °C) compared to petroleum diesel fuel, which has a flash point of 125 °F (52 °C).[39]

In many European countries, a 5% biodiesel blend is widely used and is available at thousands of gas stations.[40][41] In France, biodiesel is incorporated at a rate of 8% in the fuel used by all French diesel vehicles.[42] Avril Group produces under the brand Diester, a fifth of 11 million tons of biodiesel consumed annually by the European Union.[43] It is the leading European producer of biodiesel.[42]

Green diesel

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Main article: Biodiesel production

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.[44][45] 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.[46][47][48] 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 oils, into shorter hydrocarbon chains used in diesel engines.[49] Green diesel may also be called renewable diesel, drop-in biodiesel, hydrotreated vegetable oil (HVO fuel)[49] or hydrogen-derived renewable diesel.[45] Unlike biodiesel, green diesel has exactly the same chemical properties as petroleum-based diesel.[49][50] 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.[45] Gasoline versions are also being developed.[51] Green diesel is being developed in Louisiana and Singapore by ConocoPhillips, Neste Oil, Valero, Dynamic Fuels, and Honeywell UOP[45][52] as well as Preem in Gothenburg, Sweden, creating what is known as Evolution Diesel.[53]

Straight vegetable oil

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A biofuel truck in 2009[54]
Main article: Vegetable oil fuel

Straight unmodified 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.[28]

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.[55] The resulting product is a straight-chain hydrocarbon with a high cetane number, low in aromatics and sulfur and does not contain oxygen. Hydrogenated oils 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.[56]

Biogasoline

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Main article: 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 used modified E. 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.[57] The thermochemical approach of producing biogasoline are similar to those used to produce biodiesel.[46][47][48] Biogasoline may also be called drop-in gasoline or renewable gasoline.

Bioethers

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Neat ethanol on the left (A), gasoline on the right (G) at a filling station in Brazil in 2008

Bioethers (also referred to as fuel ethers or oxygenated fuels) are cost-effective compounds that act as octane rating enhancers. "Bioethers are produced by the reaction of reactive iso-olefins, such as iso-butylene, with bioethanol."[58][attribution needed] Bioethers are created from wheat or sugar beets, and also be produced from the waste glycerol that results from the production of biodiesel.[59] They also enhance engine performance, while significantly reducing engine wear and toxic exhaust emissions. By greatly reducing the amount of ground-level ozone emissions, they contribute to improved air quality.[61][62]

In transportation fuel there are six ether additives: dimethyl ether (DME), diethyl ether (DEE), methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME), and tert-amyl ethyl ether (TAEE).[63]

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.[64] 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.[65] 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.[66]

Aviation biofuel

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This section is an excerpt from Aviation biofuel.[edit]
Refueling an Airbus A320 with biofuel in 2011

An aviation biofuel (also known as bio-jet fuel,[67] sustainable aviation fuel (SAF), or bio-aviation fuel (BAF)[68]) is a biofuel used to power aircraft. The International Air Transport Association (IATA) considers it a key element in reducing the environmental impact of aviation.[69] Aviation biofuel is used to decarbonize medium and long-haul air travel. These types of travel generate the most emissions and could extend the life of older aircraft types by lowering their carbon footprint. Synthetic paraffinic kerosene (SPK) refers to any non-petroleum-based fuel designed to replace kerosene jet fuel, which is often, but not always, made from biomass.

Biofuels are biomass-derived fuels from plants, animals, or waste; depending on which type of biomass is used, they could lower CO2 emissions by 20–98% compared to conventional jet fuel.[70] The first test flight using blended biofuel was in 2008, and in 2011, blended fuels with 50% biofuels were allowed on commercial flights. In 2023 SAF production was 600 million liters, representing 0.2% of global jet fuel use.[71] By 2024, SAF production was to increase to 1.3 billion liters (1 million tonnes), representing 0.3% of global jet fuel consumption and 11% of global renewable fuel production.[72] This increase came as major US production facilities delayed their ramp-up until 2025, having initially been expected to reach 1.9 billion liters.

Aviation biofuel can be produced from plant or animal sources such as Jatropha, algae, tallows, waste oils, palm oil, Babassu, and Camelina (bio-SPK); from solid biomass using pyrolysis processed with a Fischer–Tropsch process (FT-SPK); with an alcohol-to-jet (ATJ) process from waste fermentation; or from synthetic biology through a solar reactor. Small piston engines can be modified to burn ethanol.

Sustainable biofuels are an alternative to electrofuels.[73] Sustainable aviation fuel is certified as being sustainable by a third-party organisation.

SAF technology faces significant challenges due to feedstock constraints. The oils and fats known as hydrotreated esters and fatty acids (Hefa), crucial for SAF production, are in limited supply as demand increases. Although advanced e-fuels technology, which combines waste CO2 with clean hydrogen, presents a promising solution, it is still under development and comes with high costs. To overcome these issues, SAF developers are exploring more readily available feedstocks such as woody biomass and agricultural and municipal waste, aiming to produce lower-carbon jet fuel more sustainably and efficiently.[74][75]

Gaseous

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Biogas and biomethane

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Biogas plant in 2007
Main article: 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.[76][77] It can be produced either from biodegradable waste materials or by the use of energy crops fed into anaerobic digesters to supplement gas yields. The solid byproduct, digestate, can be used as a biofuel or a fertilizer. 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 landfills 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.[78] Farmers can produce biogas from cattle manure via anaerobic digesters.[79]

Syngas

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Main article: 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).[56] Before partial combustion the biomass is dried and sometimes 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.[80] 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 °C.

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

Solid

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Main article: Solid fuel § Biomass

The term "biofuels" is also used for solid fuels that are made from biomass, even though this is less common.[7]

Research into other types

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Algae-based biofuels

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Main articles: Algaculture and Algae fuel

Algae can be produced in ponds or tanks on land, and out at sea.[81][82] Algal fuels have high yields,[83] a high ignition point,[84] can be grown with minimal impact on fresh water resources,[85][86][87] can be produced using saline water and wastewater, and are biodegradable and relatively harmless to the environment if spilled.[88][89] 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.[81][90]

By 2017, due to economic considerations, most efforts to produce fuel from algae have been abandoned or changed to other applications.[91]

Third and fourth-generation biofuels also include biofuels that are produced by bioengineered organisms i.e. algae and cyanobacteria.[92] Algae and cyanobacteria will use water, carbon dioxide, and solar energy to produce biofuels.[92] 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.[92] 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.[93] The disadvantages include the cost of cultivating the biofuel-producing organisms being very high.[93]

Electrofuels and solar fuels

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Electrofuels[citation needed] and solar fuels may or may not be biofuels, depending on whether they contain biological elements. Electrofuels are made by storing electrical energy in the chemical bonds of liquids and gases. The primary targets are butanol, biodiesel, and 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.[94]

Bio-digesters

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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.[95][96] 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.[97] The processes involved in anaerobic respiration are hydrolysis, acidogenesis, acetogenesis, and methanogenesis.[98]

Extent of production and use

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Biofuel production by region

Global biofuel production was 81 Mtoe in 2017 which represented an annual increase of about 3% compared to 2010.[8]: 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.[8]: 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."[8]: 11 

In 2021, worldwide biofuel production provided 4.3% of the world's fuels for transport, including a very small amount of aviation biofuel.[15] By 2027, worldwide biofuel production is expected to supply 5.4% of the world's fuels for transport including 1% of aviation fuel.[15]

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.[99]

Issues

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Wheat fields in the USA: wheat is grown for food but also for biofuel production.
This section is an excerpt from Issues relating to biofuels.[edit]

Issues relating to biofuel are social, economic, environmental and technical problems that may arise from biofuel production and use. Social and economic issues include the "food vs fuel" debate and the need to develop responsible policies and economic instruments to ensure sustainable biofuel production. Farming for biofuels feedstock can be detrimental to the environment if not done sustainably. Environmental concerns include deforestation, biodiversity loss and soil erosion as a result of land clearing for biofuels agriculture. While biofuels can contribute to reduction in global carbon emissions, indirect land use change for biofuel production can have the inverse effect. Technical issues include possible modifications necessary to run the engine on biofuel, as well as energy balance and efficiency.

The International Resource Panel outlined the wider and interrelated factors that need to be considered when deciding on the relative merits of pursuing one biofuel over another.[100] The IRP concluded that not all biofuels perform equally in terms of their effect on climate, energy security and ecosystems, and suggested that environmental and social effects need to be assessed throughout the entire life-cycle.

Environmental impacts

[edit]
Further information: Sustainable biofuels
Deforestation in Indonesia, to make way for an oil palm plantation.[101]

Estimates about the climate impact from biofuels vary widely based on the methodology and exact situation examined.[11]

In general, biofuels emit fewer greenhouse gas emissions when burned in an engine and are generally considered carbon-neutral fuels as the carbon they emit has been captured from the atmosphere by the crops used in biofuel production.[10] They can have greenhouse gas emissions ranging from as low as -127.1 gCO2eq per MJ when carbon capture is incorporated into their production to those exceeding 95 gCO2eq per MJ when land-use change is significant.[47][48] 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.[48] 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.[102][103]

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

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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 assessments of first-generation biofuels have shown large emissions associated with the potential land-use change required to produce additional biofuel feedstocks.[11][12] If no land-use change is involved, first-generation biofuels can—on average—have lower emissions than fossil fuels.[11] However, biofuel production can compete with food crop production. Up to 40% of corn produced in the United States is used to make ethanol[104] and worldwide 10% of all grain is turned into biofuel.[105] A 50% reduction in grain used for biofuels in the US and Europe would replace all of Ukraine's grain exports.[106] Several studies have shown that reductions in emissions from biofuels are achieved at the expense of other impacts, such as acidification, eutrophication, water footprint and biodiversity loss.[11]

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.[107] But the use of second-generation biofuels increases the competition for lignocellulosic biomass, increasing the cost of these biofuels.[108]

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.[109] 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.[110][111]

The European Commission has officially approved a measure to phase out palm oil-based biofuels by 2030.[112][113] 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.[114] This can provide a carbon inexpensive solution to help reduce the environmental impacts of biofuel production.

Indirect land use change impacts of biofuels

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This section is an excerpt from Indirect land use change impacts of biofuels.[edit]
Brazilian cerrado
Amazon rainforest

The indirect land use change impacts of biofuels, also known as ILUC or iLUC (pronounced as i-luck), relates to the unintended consequence of releasing more carbon emissions due to land-use changes around the world induced by the expansion of croplands for ethanol or biodiesel production in response to the increased global demand for biofuels.[115][116]

As farmers worldwide respond to higher crop prices in order to maintain the global food supply-and-demand balance, pristine lands are cleared to replace the food crops that were diverted elsewhere to biofuels' production. Because natural lands, such as rainforests and grasslands, store carbon in their soil and biomass as plants grow each year, clearance of wilderness for new farms translates to a net increase in greenhouse gas emissions. Due to this off-site change in the carbon stock of the soil and the biomass, indirect land use change has consequences in the greenhouse gas (GHG) balance of a biofuel.[115][116][117][118]

Other authors have also argued that indirect land use changes produce other significant social and environmental impacts, affecting biodiversity, water quality, food prices and supply, land tenure, worker migration, and community and cultural stability.[117][119][120][121]

See also

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References

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Biofuel

View on Grokipedia
from Grokipedia
Biofuels are combustible fuels produced from recently living , including matter, agricultural residues, , and organic wastes, through processes such as , , or , serving primarily as renewable substitutes for petroleum-derived fuels in transportation, heating, and power generation. Common types include bioethanol derived from fermenting starches or sugars in crops like corn or , biodiesel from reacting vegetable oils or animal fats with alcohol, and from microbial breakdown of waste. While advocated for potential reductions in fossil fuel dependence and , empirical assessments reveal biofuels often yield low (EROI) ratios, typically 1-4 for major feedstocks like or soy biodiesel, far below conventional oil's historical 20+ and insufficient for sustaining complex societies without subsidies. Global production surged in the due to policy mandates like the U.S. Renewable Fuel Standard and EU biofuel targets, reaching billions of liters annually, with the and dominating ethanol output from corn and sugarcane, respectively. However, causal analyses indicate these expansions have driven indirect land-use changes, including in for feedstock monocultures, offsetting claimed carbon savings and sometimes increasing net emissions. Biofuel mandates have also correlated with elevated , as crop diversions to fuel production—exemplified by corn absorbing over 40% of U.S. corn harvests—reduce supply and inflate commodity costs, exacerbating in developing regions during crises like 2008. Despite lifecycle studies showing variable environmental impacts, including from runoff and depletion, biofuels persist as politically favored due to their compatibility with existing , though first-generation variants from food crops face ongoing scrutiny for inefficient resource use compared to advanced alternatives like cellulosic or algal fuels, which remain commercially marginal.

History

Early Uses and Developments

The utilization of for dates to prehistoric eras, with of controlled burning for heating, cooking, and among early societies spanning tens of thousands of years. , formed through the slow of in low-oxygen conditions, constituted one of the earliest engineered biofuels, with archaeological traces including residues in cave paintings estimated at around years old. Liquid biofuels appeared in rudimentary forms during antiquity and the , primarily as distilled alcohols from fermented grains, fruits, or juices, though initial applications focused on illumination and solvents rather than propulsion. In the , rural produced from corn and other crop residues for lamp fuel and small engines, a practice that supported local energy needs until the imposition of a $2-per-gallon federal excise tax in 1862, which effectively suppressed non-beverage alcohol production. The advent of internal combustion engines in the late 19th century catalyzed biofuel developments for mechanical power. In 1892, Rudolf Diesel patented his compression-ignition engine, which achieved 75% thermal efficiency in prototypes and was demonstrated in 1900 at the Paris Exposition Universelle running on pure peanut oil, underscoring its compatibility with vegetable oils as high-energy-density alternatives to coal dust or petroleum. Diesel explicitly envisioned diverse fuels, including plant-derived oils from regions like the tropics, to enable decentralized energy production. Concurrently, Henry Ford promoted ethanol from farm crops as a domestic fuel to counter petroleum dependence; by 1908, his Model T's flexible carburetor permitted operation on gasoline-ethanol mixtures up to 50%, though production scaled primarily on gasoline due to cost and supply factors. These innovations laid groundwork for biofuels amid early concerns over fossil fuel finitude, though adoption waned with cheap oil post-1910s.

20th Century Advancements

In 1900, demonstrated a compression-ignition engine at the Paris Exposition that operated successfully on , illustrating the potential for vegetable oils as diesel substitutes and highlighting early recognition of biofuels' viability in internal combustion engines. Diesel's design, patented in 1892 and first operational in 1897, aimed for fuel flexibility beyond petroleum, including plant-based oils, though cheap fossil fuels later overshadowed these applications. Henry Ford incorporated ethanol compatibility into some early automobile designs, with the 1908 Model T capable of running on gasoline or ethanol blends after minor adjustments, reflecting Ford's advocacy for farm-derived alcohol fuels to support rural economies amid concerns over petroleum scarcity. By the 1920s, Ford publicly promoted ethanol from corn as a scalable alternative, establishing demonstration distilleries, though widespread adoption stalled due to Prohibition-era restrictions on alcohol production and the dominance of inexpensive gasoline. During , biofuel use expanded in resource-constrained regions; for instance, produced synthetic fuels from via processes to offset oil shortages, achieving limited but notable deployment in military vehicles. Post-war, however, surging global oil supplies suppressed biofuel development, confining it to niche agricultural or stationary engine uses until the 1970s energy crises. The 1973 Arab oil embargo, which quadrupled crude prices and exposed vulnerabilities to imported petroleum, catalyzed renewed biofuel initiatives worldwide. In the United States, this prompted federal incentives for gasohol—a 10% ethanol-gasoline blend—leading to commercial production starting in 1978, with output reaching 20 million gallons annually by 1979 to mitigate fuel shortages. Brazil's Proálcool program, enacted on November 14, , represented the era's most ambitious biofuel policy, mandating blending and subsidizing sugarcane-derived fuel to reduce imports amid . Initial production surged from 0.6 billion liters in the 1975-1976 harvest to 3.4 billion liters by 1980-1981, enabling over 90% of new vehicles to run on hydrated by the early and establishing as a pioneer in large-scale biofuel integration. The program's success stemmed from leveraging abundant resources and state-backed infrastructure, though it faced challenges from fluctuating world sugar prices and the 1979 oil shock's temporary price relief. Late-century advancements included process refinements, such as improved techniques for converting vegetable oils into esters compatible with diesel engines, spurred by ongoing oil volatility and environmental pressures. By the , pilot projects in and the U.S. demonstrated biodiesel's benefits for engines, setting the stage for , though production remained under 100 million gallons globally until policy expansions in the early 2000s. These developments underscored biofuels' role as a strategic hedge against dependence, driven by economic imperatives rather than unsubstantiated environmental claims prevalent in some academic narratives.

Modern Expansion and Policy Drivers

The expansion of biofuel production accelerated in the 1970s following the , which quadrupled global petroleum prices and exposed dependencies on imported oil, prompting governments to pursue domestic renewable alternatives for and supply diversification. In response, initiated the National Alcohol Program (Proálcool) on November 14, 1975, subsidizing production from to blend with or substitute , which by the early 1980s supported over 10 million vehicles and reduced oil imports by an estimated 40% during peak implementation. This program, backed by low-interest loans, price guarantees, and mandatory blending targets, marked one of the earliest large-scale policy-driven biofuel expansions, with output rising from 0.6 billion liters in 1975 to over 10 billion liters annually by the mid-1980s. In the United States, biofuel growth gained momentum through agricultural subsidies and mandates tied to farm policy, but modern scaling occurred via the Renewable Fuel Standard (RFS), established under the and expanded by the Energy Independence and Security Act of 2007, which required annual increases in biofuel volumes blended into transportation fuels, reaching 36 billion gallons by 2022. Primarily driven by corn-based to support domestic agriculture and reduce oil imports, the RFS correlated with U.S. production surging from 1.6 billion gallons in 2000 to 15.4 billion gallons in 2022, though critics note its reliance on food crops amid variable oil prices. Policy incentives included s, such as the volumetric extended through 2011, which lowered blending costs and boosted Midwest corn demand by about 40% of total U.S. output. European Union policies emphasized greenhouse gas reduction and renewable energy targets, with the 2003 Biofuels Directive setting initial blending goals of 2% by 2005 and 5.75% by 2010, later refined under the Renewable Energy Directive (2009/28/EC) to cap first-generation biofuels at 7% of transport energy to address indirect land-use change concerns. These mandates, coupled with national subsidies and import tariffs, drove EU biofuel consumption from negligible levels in the 1990s to 14 million tonnes of oil equivalent by 2020, though growth slowed post-2010 due to sustainability criteria prioritizing advanced biofuels. Globally, policy blends of mandates and subsidies propelled biofuel supply to approximately 140 billion liters by 2022, led by the (over 80% share), with the attributing expansion primarily to blending obligations rather than pure market forces.

Definition and Classification

Core Definitions

Biofuels are fuels produced from , encompassing , , and gaseous forms derived directly or indirectly from organic materials of biological origin. The term typically emphasizes transportation fuels such as bioethanol and , which serve as substitutes or blendstocks for petroleum-derived fuels in vehicles and engines. These fuels are generated through biological or thermochemical processes applied to feedstocks like crops, forestry residues, or waste materials, distinguishing them from fossil fuels by their reliance on renewable, short-cycle carbon sources rather than ancient, non-renewable deposits. Biomass, the foundational feedstock for biofuels, refers to from recently living plants, animals, or microorganisms, including dedicated crops (e.g., switchgrass or ), agricultural byproducts (e.g., ), forestry residues, and municipal or industrial wastes. This material captures via and stores it as in carbohydrates, , or proteins, which can then be converted into usable . Unlike fossil fuels, which result from subjected to millions of years of geological pressure and heat, for biofuels operates within annual or decadal harvest cycles, enabling regeneration and theoretically sustainable supply if managed to avoid depletion or disruption. Key attributes of biofuels include their potential for carbon neutrality in closed-loop systems, where emissions from approximate the absorbed during biomass growth, though actual lifecycle reductions depend on production efficiency, land use changes, and indirect effects like displacement of food crops. Standards bodies and agencies often classify biofuels by feedstock type or production method, but core definitions prioritize renewability and origin over specific performance metrics, with regulatory thresholds (e.g., U.S. Renewable Fuel Standard requiring at least 20% lifecycle GHG savings for certain biofuels) applied to qualify them as advanced or cellulosic variants.

Generations and Types

Biofuels are classified into generations primarily based on the type of feedstock and the technological maturity of their production processes. First-generation biofuels are derived from edible crops rich in sugars, starches, or vegetable oils, such as or . These were the earliest to be commercialized, with global production dominated by corn-based in the United States, reaching approximately 15 billion gallons annually by 2020, and in . However, their expansion has raised concerns over competition with food production and indirect land-use changes, as evidenced by studies showing increased commodity prices correlated with biofuel mandates post-2000. Second-generation biofuels utilize non-edible lignocellulosic biomass, including agricultural residues, forestry waste, and energy crops like switchgrass or . Production involves advanced processes such as enzymatic and to convert complex carbohydrates into fuels like . Commercial-scale facilities, such as those operational since 2014 in the , have demonstrated yields up to 80 gallons per dry ton of , though high costs and pretreatment challenges limit widespread adoption. These biofuels aim to mitigate food-versus-fuel trade-offs while utilizing underemployed land resources. Third-generation biofuels focus on and , which offer higher productivity—up to 10 times that of terrestrial crops—due to rapid growth and oil content exceeding 50% of dry weight. Pilot-scale production has achieved yields of 5,000-20,000 gallons per acre annually in controlled systems, but remains hindered by harvesting inefficiencies and demands. Fourth-generation biofuels incorporate , , and hybrid systems like photobiological solar fuels or electrofuels produced via microbial , potentially integrating carbon capture for net-negative emissions; however, these remain largely in research phases with no commercial output as of 2023. In parallel, biofuels are categorized by physical state: solid forms such as wood pellets and briquettes, primarily used for heat and power generation; liquid variants including bioethanol, biodiesel, and hydrotreated vegetable oils for transportation; and gaseous types like biogas (methane from anaerobic digestion) and syngas from gasification. Solid biofuels accounted for over 70% of global biomass energy use in 2022, mainly in residential heating, while liquids comprised the bulk of transport fuel blends. This dual classification highlights both evolutionary advancements in sustainability and practical applications across energy sectors.

Feedstocks and Production

Primary Feedstocks

The primary feedstocks for biofuel production consist mainly of conventional agricultural crops, including starchy grains like , sugar crops such as , and oilseeds like soybeans, , and oil palm, which together supplied approximately 660 million metric tons—or 7% of global primary crop production—in 2023 for biofuel conversion. These feedstocks dominate first-generation biofuel output due to their established supply chains, high yields of fermentable sugars or extractable oils, and compatibility with existing conversion technologies, though their use competes with food and feed demands. Maize (corn) serves as the predominant feedstock for production , where it accounts for the source in nearly all fuel , with U.S. output reaching 15.4 billion gallons in 2022 primarily from processing. Globally, contributes significantly to -based , forming part of the "other crops" category alongside and in biofuel balances projected through 2027. , conversely, is the leading sugar-based feedstock, especially in , where it underpins over 90% of production and is expected to consume about 12% of national output by 2034. For biodiesel and renewable diesel, vegetable oils from oilseeds predominate, with as the chief input in the U.S., supporting biodiesel and renewable diesel varieties that comprised the bulk of domestic biofuel capacity expansions in 2023. holds a key role in , accounting for 14% of global biodiesel feedstocks, while supplies 29%, primarily from , though its expansion has raised concerns over land-use competition. These oil crops collectively form about 70% of biodiesel inputs, with at 23% globally, reflecting regional agricultural strengths but also exposing vulnerabilities to price volatility and yield variability.
FeedstockPrimary Biofuel TypeKey RegionsApproximate Global Share in Production (2021-2027 projection)
Ethanol (starch-based)Significant in starch category
Ethanol (sugar-based)Dominant in sugars
Biodiesel/Renewable diesel, 23% of biodiesel oils
Biodiesel14% of biodiesel oils
Biodiesel29% of biodiesel oils
While wastes and residues like used cooking oil and animal fats are gaining share—projected to rise in biofuel blends through 2027—they remain secondary to these crop-based primaries, which drive the majority of the 23% global biofuel demand increase to 200 billion liters by 2028.

Key Production Processes

Biofuel production relies on biochemical and thermochemical conversion methods to transform feedstocks into usable fuels. Biochemical processes, which leverage microorganisms or enzymes, dominate first-generation biofuel output and include for and for . Thermochemical processes, such as and , are applied to lignocellulosic materials for advanced biofuels, offering higher yields from non-food sources but requiring more energy input. Fermentation converts fermentable sugars from crops like or starches from corn into . In the process, or metabolize carbohydrates under anaerobic conditions, producing and ; subsequent separates the , achieving concentrations up to 95% before to fuel-grade purity. For corn-based in the U.S., dry-milling mills kernels into , liquefies with , saccharifies it to glucose, and ferments the mash, yielding approximately 2.9 gallons of per of corn as of recent industrial averages. Wet-milling separates components first, enabling co-products like for feedstock. Efficiency improvements, including enhancements, have increased yields by integrating fiber processing, boosting output by 2.5% in U.S. facilities around 2017. Transesterification produces (fatty acid methyl esters) from vegetable oils, animal fats, or recycled greases. The reaction mixes triglycerides with in the presence of a catalyst like , forming and byproduct; excess is recovered via , and the mixture is washed to remove impurities. Industrial plants process feedstocks at ratios of 100:6-20 (oil:alcohol by weight), achieving conversion efficiencies over 95% under optimized conditions of 50-60°C and . Base-catalyzed methods are standard for low-free-fatty-acid feedstocks, while handles higher acidity, though slower. Yields typically reach 90-98% of theoretical, with comprising 10% of output mass. Anaerobic digestion generates , primarily , from wet wastes like or crop residues. Microbes in oxygen-free digesters hydrolyze organics, acidify them, acetogenize to , and methanogenize to CH4 and CO2, with retention times of 15-30 days at mesophilic (35-40°C) or thermophilic (50-55°C) temperatures. yields vary by feedstock; for example, dairy produces 20-30 m³ per , with 55-65% content upgradeable via purification to biomethane. Co-digestion of multiple wastes enhances stability and output by 20-50%. Advanced thermochemical processes like heat to 400-600°C without oxygen, yielding bio-oil (50-70% by weight), char, and ; fast pyrolysis maximizes liquids for upgrading to hydrocarbons. partially oxidizes at 700-1000°C to produce (CO, H2) for Fischer-Tropsch synthesis into diesel or alcohols, with efficiencies of 40-60% on energy basis from woody feedstocks. These methods suit , circumventing food competition but facing scale-up challenges in catalyst durability and tar removal.

Major Biofuel Types

Liquid Biofuels

Liquid biofuels consist of fuels in form derived from feedstocks, primarily serving as substitutes or blendstocks for petroleum-based transportation fuels such as and diesel. These fuels include alcohols like and , as well as fatty acid esters like , produced through biochemical or thermochemical conversion processes. Unlike solid or gaseous biofuels, variants offer compatibility with existing internal combustion engines and infrastructure, facilitating their adoption in road vehicles, , and shipping. Production volumes in 2023 totaled approximately 116 billion liters for alone, representing about 70% of global biofuel output, with contributing the remainder. Bioethanol, the most widely produced liquid biofuel, results from the of fermentable sugars extracted from starch- or sugar-rich crops such as corn, , or . In the United States, dry-mill facilities predominate, grinding corn kernels to produce starch hydrolysates that ferments into , followed by and to achieve fuel-grade purity exceeding 99%. Global production leaders include the , with over 15 billion gallons annually as of 2022, and , leveraging for efficient yields of up to 8,000 liters per . Lifecycle analyses indicate that corn-based reduces by about 12% compared to , though this figure varies with farming practices and coproduct credits; achieves 40-60% reductions due to higher yields and no-till methods. Biodiesel production involves transesterification, where triglycerides from vegetable oils (e.g., , ) or animal fats react with in the presence of a like to form methyl esters and byproduct. This process yields a drop-in fuel blendable with diesel at ratios up to 20% (B20) without modifications. U.S. biodiesel capacity expanded 7% in 2023 to support over 3 billion gallons annually, primarily from amid rising demand for renewable diesel variants produced via hydrotreating. Relative to fossil diesel, biodiesel combustion cuts particulate matter, , and air toxics, with lifecycle GHG savings of 41-86% depending on feedstock; however, soy-based variants can increase emissions and face criticism for indirect land-use changes exacerbating when scaled. Advanced liquid biofuels, such as and hydrotreated esters and fatty acids (HEFA), address limitations of first-generation fuels by utilizing non-food lignocellulosic feedstocks like agricultural residues, forestry waste, or . employs enzymatic to break down and into sugars for , followed by ; commercial-scale facilities, though limited, achieved yields of 250-300 liters per dry ton of in pilots as of 2022. HEFA pathways hydrotreat oils to produce renewable diesel or , offering superior cold-flow properties and up to 90% GHG reductions versus equivalents, but scalability hinges on availability amid competition from sectors. These second- and third-generation options mitigate food-versus-fuel trade-offs but incur higher upfront costs, with enzymatic pretreatments adding 20-50% to production expenses compared to conventional routes. Empirical data from lifecycle assessments underscore that indirect effects, such as runoff and loss, can erode net environmental gains unless managed through sustainable sourcing.

Gaseous Biofuels

Gaseous biofuels encompass fuels derived from via biochemical or thermochemical conversion processes, primarily including , biomethane, and . These gases serve as renewable alternatives to fossil for applications in heating, , and transportation. Biogas results from the of organic feedstocks such as agricultural residues, animal manure, municipal waste, and energy crops, where microbial decomposition produces a typically containing 50-70% (CH₄), 30-50% (CO₂), and trace amounts of (H₂S) and other impurities. This process occurs in digesters under oxygen-free conditions at mesophilic (30-40°C) or thermophilic (50-60°C) temperatures, with retention times of 15-30 days depending on feedstock and design. Globally, production in 2023 supported an installed capacity of 11 GW for power generation, concentrated in , , and the , which together account for 90% of output. Biomethane, also known as , is produced by upgrading raw to remove CO₂, H₂S, , and siloxanes, achieving purity exceeding 96% for compatibility with infrastructure. Common upgrading technologies include (PSA), water scrubbing, chemical absorption (e.g., using amines or selexol), and separation, with PSA and water scrubbing dominating due to their efficiency and cost-effectiveness for medium-scale plants. The resulting biomethane can be injected into gas grids or compressed for use as vehicle fuel, contributing to decarbonization in sectors hard to electrify. Syngas, or synthesis gas, is generated through thermochemical of solid feedstocks like wood chips, agricultural residues, or at temperatures above 700°C in the presence of limited oxygen, steam, or CO₂, yielding a combustible mixture primarily of (CO), (), (), and CO₂. occurs in reactors such as fixed-bed, fluidized-bed, or entrained-flow types, with composition varying by feedstock, temperature, and gasifying agent—typically 20-30% CO, 10-20% , and lower fractions of and CO₂ for air-blown processes. This serves as a precursor for biofuels via Fischer-Tropsch synthesis or methanol production, or directly for power via gas turbines after cleaning to remove tar, particulates, and compounds. Global demand for biogases, including both and biomethane, is projected to rise by approximately 30% from 2024 to 2030, reaching nearly 2 billion cubic meters equivalent amid policy support for and renewable gas targets. However, commercialization faces challenges such as feedstock variability, process efficiency (e.g., gasification cold gas efficiency of 50-70%), and the need for robust gas cleaning to meet end-use specifications. Sustainable production potential from and waste could supply up to a quarter of current global demand if fully realized.

Solid Biofuels

Solid biofuels encompass densified or unprocessed biomass materials, such as wood pellets, chips, briquettes, and agricultural residues like or husks, derived from , agricultural, and dedicated crops. These fuels are combusted directly to produce , , or , distinguishing them from liquid or gaseous biofuels that require conversion into transportable forms. Primary feedstocks include residues, byproducts, and herbaceous plants such as switchgrass or , which are harvested, dried to contents below 15-20% for efficient , and processed mechanically. Production involves minimal chemical alteration, focusing on size reduction via chipping or grinding, followed by optional densification through pelletizing—where biomass is extruded under high pressure (up to 100 MPa) at temperatures of 80-200°C to form uniform cylinders 6-8 mm in diameter—or briquetting for larger blocks. Torrefaction, a mild pyrolysis at 200-300°C in low-oxygen conditions, enhances energy density by removing volatiles and improving hydrophobicity, yielding a coal-like product with higher calorific values (20-25 MJ/kg versus 15-18 MJ/kg for untreated wood). Global output relies on abundant residues; for instance, forestry provides over 50% of solid biofuel feedstocks in Europe, with pellet production exceeding 50 million tonnes annually as of 2022. Applications center on stationary uses, including residential stoves, industrial boilers, and co-firing in coal plants (up to 20-30% substitution rates without major retrofits), as well as district heating systems. In power generation, solid biofuels enable baseload renewable output due to their storability and high energy density post-densification (e.g., pellets at 16-18 MJ/kg). The European Union produced 87.6 TWh of electricity from solid biofuels in 2022, led by Finland (19 TWh), Sweden (17 TWh), and Germany (12 TWh), reflecting mature district heating infrastructure. Globally, modern solid bioenergy constitutes approximately 75% of renewable fuel demand, with total biomass energy equivalent to 1.4 billion tonnes of oil equivalent annually, though modern processed forms represent a growing subset amid stabilizing traditional wood use. While solid biofuels offer dispatchable energy with lower sulfur and nitrogen content than (typically <0.1% sulfur versus 1-3% in ), generates particulate matter and unless mitigated by filters or advanced boilers. Lifecycle reductions of 70-90% versus fossil s are achievable with sustainable sourcing, but vary with transport distances and ; unsustainably harvested can increase net emissions due to loss. Economic viability hinges on local supply chains, with pellet costs ranging $150-250 per in 2023, competitive in regions with subsidies or carbon pricing. Challenges include seasonal availability and moisture variability, addressed through storage silos and preprocessing, positioning solid biofuels as a bridge in decarbonizing and power sectors.

Global Production and Consumption

Production Statistics

Global liquid biofuel production totaled approximately 166 billion liters in 2023, comprising 116 billion liters of (70% of the total) and nearly 50 billion liters of (FAME) biodiesel. output was led by the and , which together accounted for 80% of global production, with the U.S. producing around 58 billion liters and 32 billion liters. emerged as the third-largest producer at about 11 billion liters, driven by policy mandates for blending with . Biodiesel production was more regionally diverse, with at the forefront using feedstocks to yield 14 billion liters, followed by the at 13 billion liters from and other oils. The U.S. contributed around 8 billion liters of and renewable diesel combined, supported by federal blending incentives. and rounded out key producers, with volumes of approximately 4 billion and 3 billion liters, respectively, reflecting reliance on soy and palm oil. Production growth has moderated in recent years, with global volumes rising about 5% annually from 2020 to 2023, compared to double-digit gains in the prior decade, amid feedstock constraints and competition from electric vehicles. In the U.S., biofuel capacity expanded 7% in 2023 to 24 billion gallons (91 billion liters) by early 2024, primarily from renewable diesel additions, though actual output lagged capacity utilization at around 80%. Projections indicate total biofuel production approaching 200 billion liters by 2028, with advanced biofuels like hydrotreated vegetable oil (HVO) gaining share in Europe and North America.
Biofuel TypeGlobal Production (2023, billion liters)Top Producers (billion liters)
Ethanol116U.S. (58), (32), (11)
Biodiesel (FAME)~50 (14), (13), U.S. (8)
Solid and gaseous biofuels, such as wood pellets and , add to the broader tally but represent smaller shares in transport-focused statistics; global pellet production reached 62 million tons in 2023, mainly for and power. Data from sources like the World Bioenergy Association emphasize first-generation feedstocks' dominance, with advanced pathways scaling slowly due to higher costs. In early 2026, the USDA released Biofuels Annual reports for Canada and Taiwan, providing updated assessments of their biofuel production capacities and policies. The EIA updated its U.S. biofuels production data as of February 2026.

Consumption Patterns and Trade

Liquid biofuels are predominantly consumed in the transport sector, accounting for over 90% of global biofuel use, with vehicles utilizing blended fuels such as in and in diesel. In 2023, global biofuel demand stood at approximately 162 billion litres, driven mainly by mandates in major economies. Demand is projected to grow by 38 billion litres between 2023 and 2028, representing a 23% increase, with and renewable diesel comprising two-thirds of this expansion. The , Brazil, and the dominate consumption patterns, together accounting for over 70% of global liquid biofuel use. In the , consumption reached about 15 billion gallons in 2023, primarily through E10 blends in vehicles, supported by the Renewable Fuel Standard. Brazil's consumption, heavily reliant on sugarcane , exceeded 30 billion litres in 2023, facilitated by widespread flex-fuel vehicles and mandatory blending up to 27%. The consumed around 15 million tonnes of in 2022, with leading at approximately 49,000 barrels per day, driven by Renewable Energy Directive targets. Emerging markets like and are increasing consumption through higher blending mandates, contributing to growth in advanced biofuels like renewable diesel. Biofuel trade volumes remain modest relative to production, typically 10-20% internationally traded, limited by local production incentives and tariffs. The emerged as the leading exporter in 2024, shipping a record 1.9 billion gallons valued at $4 billion, with (35%), the (13%), and the (10%) as primary destinations. For , the ranked as the top global exporter in 2023, followed by and traditional producers like supplying the EU market. U.S. exports in 2024 targeted , , and , totaling over $570 million, while imports fell to near 10 million barrels amid domestic policy changes. occasionally imports during shortages but remains a net exporter overall, underscoring trade's role in balancing regional supply-demand imbalances. In early 2026, Brazilian corn ethanol producer Inpasa ramped up exports of dried distillers grains with solubles (DDGS), a co-product of biofuel production, to China, securing contracts for up to 1.5 million tons.
Top Ethanol Exporting Country (2024)Volume (billion gallons)
1.9
Top Biodiesel Consuming Countries (latest available)Thousand Barrels per Day
60,000
49,000
48,000

Economic Analysis

Production Costs and Competitiveness

Biofuel production costs are dominated by feedstock expenses, which typically comprise 60-90% of total outlays for first-generation variants, with additional contributions from conversion processes, capital depreciation, and logistics. For bioethanol, sugarcane-based production in achieves low costs of 0.20-0.30 USD per liter, leveraging high agricultural yields, efficient milling, and revenue from co-products for energy self-sufficiency. Corn-based ethanol in the United States, by contrast, incurs higher expenses, with recent estimates placing production at approximately 0.40-0.53 USD per liter (equivalent to 1.50-2.00 USD per ), sensitive to corn price volatility and dry-grind processing efficiencies. Biodiesel from vegetable oils like or palm exhibits costs of 1.00-1.24 USD per liter in commercial settings, exceeding fossil diesel production by 20-50% under typical crude oil prices of 70-90 USD per barrel. Advanced biofuels, such as or (HVO), face elevated upfront capital and enzymatic/pre-treatment costs, often 1.5-3 times those of first-generation equivalents, though experience curves suggest potential declines—ethanol production costs have historically reduced at a 21.8% with cumulative output scaling. Feedstock sourcing remains a key variability factor; waste oils or residues lower expenses to as little as 0.80 USD per liter in optimized cases, but supply constraints limit scalability.
Biofuel TypePrimary Feedstock/RegionEstimated Production Cost (USD/L)Key Cost Drivers
Sugarcane Bioethanol/Brazil0.20-0.30Low feedstock yield costs, co-products
Corn BioethanolCorn/0.40-0.53 prices (70-80% of total),
Vegetable Oil BiodieselSoy/Palm/Global1.00-1.24 extraction (60-80%),
HVO/Renewable DieselWaste oils/Europe1.50-2.00, refinery integration
Biofuels exhibit limited standalone competitiveness against fossil fuels, which benefit from established and lower marginal costs—biofuels typically add 0.01-0.04 USD per liter to blended prices despite mandates. In , sugarcane achieves occasional parity with during oil price spikes above 80 USD per barrel, but U.S. corn and European rely heavily on blending mandates, tax credits, and renewable credits like RINs, whose prices fell 45% in early 2024 amid oversupply. Without such distortions, higher and scalability of derivatives prevail, though biofuel cost trajectories could improve via yield enhancements and waste utilization, contingent on sustained investment.

Subsidies, Incentives, and Market Distortions

Governments have deployed various subsidies, tax credits, and blending mandates to bolster biofuel adoption, ostensibly to enhance , reduce emissions, and support rural economies. In the United States, the Renewable Fuel Standard (RFS), enacted via the and expanded in 2007, mandates minimum volumes of in transportation, escalating to 36 billion gallons annually by 2022, with ongoing adjustments for subsequent years. These mandates generate implicit subsidies through enforced demand, imposing compliance costs on refiners estimated at $2.84 billion for certain periods, equivalent to about 2.2 cents per gallon of blended gasoline. The 2022 further allocates roughly $9.4 billion in production and investment tax credits for biofuels through 2031. In the , the Renewable Energy Directive (RED), revised as RED III in 2023, targets at least 42.5% renewable energy in final consumption by 2030, including biofuel blending requirements that drive market uptake and correlate with emissions reductions in transport. enforces ethanol blending up to 27% and up to 14% (as of 2024), underpinned by tax incentives and low-interest loans from the National Biofuels Program, contributing to record production of 7.5 billion liters of in 2023. These mechanisms distort markets by subsidizing production costs and compelling consumption, often rendering biofuels competitive only through intervention rather than intrinsic . Mandates and credits divert agricultural feedstocks from and feed markets, elevating crop prices; U.S. ethanol policies, for example, have increased corn prices by approximately 24% while reducing prices by 8% in modeled 2022 scenarios. This feedstock competition amplifies global price volatility, as observed during the 2007-2008 crisis and persisting in subsequent periods, disproportionately burdening low-income households in developing regions. Subsidies also incentivize suboptimal land use, prompting conversion of arable land to biofuel monocultures and indirect expansion into forests or marginal areas, which can negate greenhouse gas savings and harm biodiversity. Economic analyses indicate that without such interventions, biofuel expansion would contract due to higher production costs relative to fossil alternatives, leading to resource misallocation where capital and labor shift from potentially higher-value uses. Consumer burdens from RFS compliance alone have been estimated in the tens of billions over program lifetimes, underscoring opportunity costs for unsubsidized low-carbon alternatives. Overall, these policies foster dependency on government support, with critics noting that biofuels' viability hinges on distortions that elevate systemic inefficiencies rather than genuine market signals.

Environmental and Resource Impacts

Lifecycle Greenhouse Gas Emissions

Lifecycle greenhouse gas (GHG) emissions for biofuels encompass emissions across the full , including feedstock cultivation, harvesting, processing, transportation, distribution, and end-use , as well as upstream effects like production and downstream credits from co-products. Unlike tailpipe-only assessments, this approach accounts for biogenic carbon neutrality assumptions, where CO2 absorbed during plant growth offsets releases, but net savings depend on non-CO2 emissions such as , (N2O), and those from change (LUC). Direct LUC from clearing forests or grasslands for biofuel crops can release stored carbon, while indirect LUC (ILUC) arises from displaced production leading to expansion elsewhere; modeling ILUC remains contentious due to economic assumptions and data uncertainties. Empirical assessments show biofuel GHG reductions relative to fossil fuels vary widely by feedstock, yield, and practices, often ranging from negligible to over 80% savings, but many first-generation pathways fail to achieve substantial net benefits when ILUC is included. For U.S. , updated lifecycle models incorporating improved farming and lower ILUC estimates project 39-43% reductions compared to as of 2018 data extended to recent trends, though earlier EPA analyses under the Renewable Fuel Standard pegged average savings at 21% including ILUC. from demonstrates stronger performance, with lifecycle savings of 78% versus , driven by high yields, for process energy, and minimal ILUC in established plantations. Biodiesel and renewable diesel from oilseeds like soy or palm exhibit 40-86% reductions when sourced from waste greases or low-impact crops, but biodiesel frequently underperforms or increases emissions due to peatland drainage and ; a 2020 field study in found measured emissions from palm plantations exceeded diesel equivalents by up to 50% when including and LUC fluxes. N2O emissions from fertilizers, which can comprise 50-90% of agricultural GHG, further erode savings in crop-based pathways, while advanced feedstocks like or cellulosic residues promise 80-90% cuts but remain commercially limited as of 2025. Regulatory thresholds, such as the EU Renewable Energy Directive's 50-65% savings requirement, highlight that only select pathways qualify without ILUC adjustments, underscoring model sensitivities.
Biofuel TypeFeedstock ExampleLifecycle GHG Savings vs. Fossil Fuel (%)Key Factors Influencing EmissionsSource
EthanolCorn (U.S.)21-43ILUC modeling, fertilizer N2O
EthanolSugarcane (Brazil)78High yield, biomass energy use
BiodieselSoy/Waste Oils40-86Allocation methods, waste vs. crop
BiodieselPalm Oil-50 to +50 (net increase possible)Deforestation, peat oxidation
Overall, while some biofuels like deliver verifiable reductions supported by field data and process efficiencies, others, particularly from annual food crops, risk negligible or negative impacts if expansion drives high-carbon LUC, as evidenced by discrepancies between optimistic industry models and conservative peer-reviewed measurements emphasizing causal emission pathways over policy-driven assumptions.

Land Use Change and Biodiversity Effects

The expansion of biofuel feedstocks, particularly first-generation crops such as oil palm, soybeans, and corn, has driven significant direct and indirect land use changes (LUC), converting forests, grasslands, and other natural habitats into monoculture plantations and arable land. This process releases stored carbon, erodes soil, and fragments ecosystems, with global analyses indicating that replacing natural vegetation with bioenergy crops results in net biodiversity declines across most assessed locations. For instance, a spatially explicit assessment found that first-generation biofuel expansion causes relative species loss exceeding that of fossil fuel production in over 90% of global sites, due to the lower productivity and higher habitat demands of crop-based systems compared to native vegetation. In tropical regions, biofuel demand has accelerated , notably for in and , where plantations supplied feedstocks for meeting EU renewable targets. Between 2018 and 2022, industrial expansion accounted for an average of 32,406 hectares of annual , down from peaks over 100,000 hectares per year a decade earlier but still contributing to habitat loss for species like orangutans and Sumatran tigers. cultivation for in Brazil's Amazon and biomes historically linked to 13-18% of direct , though recent data show decoupling in the Amazon since 2006, with agricultural intensification on existing lands reducing clearance rates to 30% of prior averages by 2010. Indirect LUC from displaced food production, however, persists, as biofuel mandates elevate commodity prices and incentivize expansion into uncleared areas. In the United States, corn ethanol production under the Renewable Fuel Standard has expanded corn acreage by approximately 884 acres per million gallons of additional capacity, intensifying farming on marginal lands and contributing to conversion, which harbors higher native than row crops. Empirical studies estimate negligible overall ILUC for U.S. , with total cropland increase limited despite 15 billion gallons produced annually, but critics highlight unmeasured costs from and pesticide runoff. These effects compound globally, as analyses from 1995 to 2022 link agricultural demand—including biofuels—to erosion via habitat loss exceeding natural regeneration rates in high-conversion zones. efforts, such as schemes, have slowed but not eliminated these impacts, underscoring the causal tension between biofuel scale-up and ecosystem integrity.

Water Usage and Pollution

Biofuel production, especially first-generation variants reliant on crops like corn and sugarcane, imposes a substantial water footprint, predominantly from irrigation and evapotranspiration during feedstock cultivation. Lifecycle assessments indicate that corn ethanol requires 10-17 liters of blue water (withdrawn from surface or groundwater) per liter of ethanol, though total footprints including green water (rainfall) can reach 263-784 liters per liter from farm to pump, or up to 2,854 liters globally when accounting for all inputs. Sugarcane ethanol similarly demands high volumes, with estimates of 2,860 liters per liter in water-stressed regions like India, driven by the crop's irrigation needs in dry seasons. These demands can strain local aquifers and rivers, particularly in arid production areas, where only 4% of U.S. corn for ethanol is irrigated but still consumes an average of 785 gallons of irrigation water per gallon of ethanol in those cases. Process water at conversion facilities adds 3-4 gallons per gallon of ethanol, often recycled but still contributing to overall consumption. Water footprints vary by feedstock and region; cellulosic biofuels from residues or perennials generally require less, with estimates of 1.9-9.8 liters per liter for switchgrass , compared to gasoline's 2.8-6.6 liters per liter equivalent. However, scaling biofuel mandates amplifies aggregate use: global biofuel production's reached 0.028 billion cubic meters in 2010, projected to rise with expanded output. In water-scarce contexts, this competes with food production and ecosystems, potentially exacerbating shortages without efficient or drought-resistant varieties. Pollution from biofuel feedstocks arises mainly from agricultural practices, including and , which generate runoff into waterways. and from fertilizers cause , leading to hypoxic zones; production, for instance, releases higher levels of these nutrients per energy unit than or . Pesticides and herbicides contaminate surface and , harming aquatic life and , with intensive systems amplifying risks through and chemical leaching. Processing stages contribute additional pollutants: untreated wastewater from ethanol or biodiesel facilities discharges organic matter, boosting and further risks. Soy-based biodiesel mitigates some impacts, emitting only 1-13% of ethanol's agricultural , , and pesticides per net gained. Empirical data underscore that while biofuels reduce tailpipe emissions, upstream often offsets gains unless mitigated by precision farming or , as evidenced in U.S. Midwest watersheds affected by corn expansion.

Key Criticisms and Debates

Net Energy Return and Efficiency

Net energy return, often quantified as (EROI), measures the ratio of usable output from a to the input required for its production, , and delivery. For biofuels, EROI calculations typically encompass the full lifecycle, including , harvesting, conversion, and distribution, revealing frequent challenges in achieving positive net gains. Empirical assessments indicate that many first-generation biofuels yield EROIs below 4:1, a threshold some analysts deem insufficient for scalable societal systems, as it implies limited surplus after accounting for production costs. Specific EROI values vary by feedstock and methodology but consistently show lower returns for crop-based biofuels compared to fuels. Corn-based ethanol in the United States has an EROI of approximately 1.04:1, while sugarcane ethanol reaches about 1.80:1, and palm oil biodiesel around 3.05:1. A of biofuel studies estimates an average EROI of 3.92:1 across generations, categorizing it as marginally positive yet the lowest among renewables like or solar. These figures arise from energy-intensive inputs such as fertilizers, , and , which can exceed outputs in inefficient systems; for instance, from wood residues yields only 0.74:1 under certain conditions.
Biofuel TypeFeedstock ExampleEROI Ratio
EthanolCorn1.04:1
Ethanol1.80:1
3.05:1
EthanolWood residues0.74:1
In comparison, conventional crude oil historically delivered EROIs of 20:1 to 100:1, though modern extraction methods like reduce this to 5:1–10:1, still surpassing most biofuels. Coal maintains higher values around 20:1–80:1 depending on mining . Critics argue that biofuels' low EROI undermines their role as a substitute, as the net energy surplus fails to support or infrastructure expansion without subsidies distorting markets. Lifecycle analyses highlight further inefficiencies, where indirect energy costs—like those from land preparation or —erode apparent gains, particularly for food-crop biofuels. Debates center on EROI boundaries and assumptions, with proponents of biofuels claiming higher values (up to 5:1–10:1) by excluding societal overheads or crediting co-products like . However, rigorous peer-reviewed harmonizations confirm that even optimistic estimates rarely exceed 4:1 for first-generation variants, rendering them inefficient for needs. Advanced second- and third-generation biofuels from or wastes promise improvements but remain unproven at scale, with pilot EROIs still below fossil benchmarks due to processing hurdles. Overall, suggests biofuels often function more as energy sinks than net providers, challenging claims of inherent efficiency advantages over conventional sources.

Food Security and Indirect Land Use

The production of first-generation biofuels, derived from food crops such as corn, soybeans, and , directly competes with food and feed supplies by diverting , , and other resources. In the United States, for instance, approximately 40 percent of the corn crop was used for production in recent years, reducing availability for human consumption and . This diversion has been linked to elevated commodity prices, exacerbating particularly in low-income households and developing nations where staple foods like form a dietary staple. Empirical analyses indicate that biofuel mandates contributed to higher global , with studies estimating that biofuel expansion accounted for 20 to 40 percent of price increases during periods of volatility. The 2007–2008 global food price crisis highlighted these tensions, as surging demand for biofuel feedstocks amid policy-driven expansion coincided with sharp rises in staple costs, affecting over 100 million in hunger hotspots. Biofuel production diverted significant volumes of and oilseeds, with U.S. ethanol alone absorbing an estimated 100 million tons of corn equivalent during peak years, amplifying price pressures through reduced supply elasticity. While other factors like oil prices and weather events played roles, econometric models attribute a substantial share of the crisis—up to one-third of corn price hikes—to biofuel policies, underscoring causal links between mandates and food access disruptions in vulnerable regions. Indirect land use change (ILUC) arises when biofuel-induced demand for crops displaces existing agricultural production, prompting expansion into uncultivated areas such as forests or grasslands to maintain food output. This phenomenon, modeled through global economic frameworks like GTAP, generates additional from —estimated at 17 to 420 grams of CO2 equivalent per megajoule of biofuel depending on feedstock and location—but also strains by shifting cultivation to less productive or ecologically fragile lands, potentially lowering overall yields and increasing reliance on imports. Peer-reviewed assessments confirm ILUC effects for crops like soy and , where Brazilian or Indonesian biofuel booms correlated with Amazon or Southeast Asian clearing to offset displaced soy or palm for food markets. However, ILUC estimates vary widely due to modeling assumptions on market elasticities and leakage rates, with some empirical validations showing lower realized impacts than initial projections. In developing countries, ILUC exacerbates risks by prioritizing export-oriented biofuel crops over local staples, as seen in African nations where plantations on reduced community production without commensurate benefits. Studies across 51 developing economies from 2011 to 2016 found biofuel expansion correlated with diminished food availability metrics, though advanced feedstocks like wastes mitigate these effects. Policymakers have responded with ILUC in regulations, such as the EU's Directive adjustments, yet uncertainties in attribution persist, emphasizing the need for empirical monitoring over speculative models.

Overstated Environmental Benefits

Proponents of biofuels have frequently claimed substantial reductions in (GHG) emissions compared to fossil fuels, often citing direct combustion savings without fully accounting for lifecycle emissions. However, multiple peer-reviewed analyses indicate these benefits are overstated, particularly when indirect land use change (ILUC) and are incorporated into models. For instance, ILUC emissions from biofuel expansion can exceed direct savings, resulting in net GHG increases; studies estimate that such effects may more than offset the advantages of replacing fossil fuels with crop-based biofuels. In the case of , widely promoted in the United States under the Renewable Fuel Standard, independent research challenges the environmental superiority asserted by industry groups. A analysis published in Proceedings of the found that U.S. corn ethanol production leads to higher lifecycle GHG emissions than , driven by cropland expansion and intensified farming practices that release stored and . This contradicts earlier EPA models, which some critiques argue underestimated tailpipe benefits but more critically overlooked comprehensive land conversion impacts, rendering net reductions negligible or negative. Palm oil biodiesel exemplifies even greater overstatement, with production linked to extensive tropical and . Lifecycle assessments reveal that palm-derived can emit up to three times more CO2 than conventional diesel when factoring in land clearance emissions, as peatland drainage and conversion release massive carbon stores. A 2019 European Commission study confirmed that palm and soy oil biofuels contribute 16% more global CO2 than the fossil fuels they displace, undermining claims of . Indonesia's push for B30 blends since 2020 has accelerated this trend, prioritizing export revenues over verified emission cuts. Critics further note that standard lifecycle assessments (LCAs) often exclude non-CO2 emissions like from decay or full inefficiencies, inflating perceived benefits by 20-50% in some models. While from wastes show promise for genuine reductions (40-86% versus ), first-generation feedstocks dominate global production, perpetuating the discrepancy between policy rhetoric and empirical outcomes. This pattern highlights systemic in early biofuel evaluations, where direct fuel-cycle metrics overshadowed holistic causal impacts.

Policy Frameworks

Historical and Current Policies

Biofuel policies originated primarily as responses to concerns during oil crises in the , with governments implementing subsidies, tax incentives, and blending mandates to promote domestic production and reduce reliance on imported . In , the Proálcool program launched in 1975 subsidized production from , mandating initial blends and offering price supports to counter the 1973 oil shock, which evolved into a nationwide flex-fuel vehicle infrastructure by the 2000s. The introduced incentives in the late under President , including a 40-cent per gasohol , followed by the 1992 Act's clean-fuel vehicle requirements and the 2005 Renewable Fuel Standard (RFS) mandating 7.5 billion gallons of renewable fuel by 2012, primarily . In the , early efforts in the 1990s focused on member-state tax reductions, culminating in the 2003 Biofuels Directive setting indicative targets of 2% biofuel share in transport fuels by 2005, rising to 5.75% by 2010. The 2000s saw policy expansion driven by climate goals alongside , with the U.S. Energy Independence and Security Act of 2007 amending the RFS to require 36 billion gallons by 2022, including 21 billion from conventional biofuels like and 16 billion from advanced sources such as cellulosic. Brazil's National Biodiesel Production and Use Program (PNPB), established via Law 11.097 in 2005, introduced mandatory diesel blends starting at 2% in 2008, increasing to 5% by 2010, sourced largely from . The EU's 2009 Renewable Energy Directive (RED I) targeted 10% in by 2020, incorporating sustainability criteria requiring at least 35% greenhouse gas savings over fossils, though actual penetration reached only about 5.5% amid concerns over indirect land-use change. As of 2025, U.S. policy under the RFS continues with annual volume targets set by the , emphasizing advanced biofuels while comprises over 90% of blending; the Volumetric Excise Tax Credit provides $1.00 per gallon for blends through 2024 extensions, though debates persist on waivers due to cellulosic shortfalls. In early 2026, delays in finalizing 2026 biofuel quotas under the RFS have caused uncertainty for grain traders like ADM and Bunge, leading to cautious profit forecasts amid policy and trade issues. In the , the revised RED II (2018) mandates 14% in transport by 2030, capping food-based biofuels at 7% and prioritizing waste-derived and advanced options with higher GHG thresholds (65% savings); member states enforce blends up to E10 for and B7 for , supported by double-counting for certain biofuels. , under the RenovaBio framework since 2017, issues decarbonization credits to producers based on lifecycle emissions, with June 2025 adjustments raising mandatory blending to 30% (E30) and to 15% (B15) to enhance self-sufficiency and emissions reductions. Globally, over 80 countries maintain biofuel support mechanisms, per IEA assessments, though implementation varies with blending mandates dominant in emerging markets. For instance, Indonesia plans to raise mandatory bioethanol blending in gasoline to 10% by 2028 to reduce imports, though analyses indicate that competition from affordable electric vehicles could undermine these biofuel expansion efforts.

International Agreements and Mandates

The absence of a comprehensive global mandating biofuel production or blending distinguishes international biofuel frameworks from national policies, with over 80 countries implementing domestic mandates or targets to support biofuel demand, often aligned with broader objectives. These national measures, such as blending requirements, are influenced by disciplines rather than direct mandates, ensuring biofuels are treated as commodities under general WTO agreements without a sector-specific regime. Since 2000, WTO members have notified 37 technical measures related to biofuels under the Agreement on Technical Barriers to Trade, facilitating transparency in standards for production, , and criteria. The plays a central role in adjudicating biofuel trade disputes, enforcing principles of non-discrimination and proportionality in measures affecting . In 2025, a WTO panel ruled in favor of in its challenge against anti-dumping duties on imports, finding that the European Commission's calculations overstated subsidies and injury to domestic producers, though it upheld some aspects of the duties. Similarly, disputes involving sustainability standards for palm oil-based biofuels, such as those limiting high indirect land-use change risk feedstocks, have tested WTO compatibility, with panels affirming environmental justifications but requiring evidence-based implementation to avoid undue trade restrictions. These rulings underscore tensions between biofuel promotion for emissions reduction and trade fairness, particularly for exporters like and reliant on crop-based feedstocks. In , the International Civil Aviation Organization's Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), implemented in phases with mandatory participation for larger operators from 2024, incentivizes biofuel-derived sustainable aviation fuels (SAF) by allowing their use to reduce offsetting obligations. CORSIA-eligible fuels, including certain biofuels, must demonstrate at least a 10% lifecycle reduction compared to conventional baselines, promoting advanced feedstocks while accommodating international supply chains. This framework, covering international flights responsible for about 2% of global CO2 emissions, indirectly mandates emissions management but relies on voluntary SAF uptake rather than fixed blending quotas. Under the , biofuels feature in nationally determined contributions (NDCs) of multiple parties as a tool for transport sector decarbonization, though without enforceable international mandates; for instance, and specify biofuel blending to meet mitigation targets, reflecting voluntary alignment with global goals rather than binding obligations. Such integrations highlight biofuels' role in Nationally Determined Contributions but emphasize that mandates remain sovereign, subject to international scrutiny via trade bodies like the WTO to prevent disguised as .

Research and Future Developments

Advanced and Next-Generation Biofuels

Advanced biofuels refer to fuels derived from non-food feedstocks such as , agricultural and forestry residues, municipal wastes, and , distinguishing them from first-generation biofuels produced from edible crops like corn or . These feedstocks aim to mitigate concerns and indirect land use changes associated with conventional biofuels. Next-generation biofuels encompass third-generation variants, particularly algal-based systems, and emerging pathways involving or hybrid processes to enhance yields and efficiency. Key technologies for advanced biofuels include biochemical routes like enzymatic followed by for , and thermochemical methods such as coupled with Fischer-Tropsch synthesis for drop-in hydrocarbons compatible with existing . Algal biofuels leverage microalgae's high content and rapid growth rates, potentially yielding 10-20 times more oil per hectare than terrestrial crops, though harvesting and extraction remain technically demanding. Demonstration facilities worldwide, tracked by organizations like IEA Bioenergy, produce these via processes including alcohol-to-jet (ATJ) and fast , but commercial-scale output remains limited. As of 2024, cellulosic biofuel production in the United States generated approximately 1.09 billion Renewable Identification Numbers (RINs) as projected by the EPA, though volumes fell short of mandates, prompting partial waivers due to insufficient supply. Globally, advanced biofuel markets were valued at around USD 1.46 billion in 2024, with algal segments showing fastest growth potential but no widespread commercial viability yet. In the European Union, production focuses on waste-derived biodiesel and biojet, yet total advanced biofuel output constitutes less than 1% of transport fuel demand. Scaling challenges persist, including high capital costs—often 2-3 times those of first-generation plants—feedstock pretreatment difficulties for recalcitrant lignocellulosics, and unfavorable economics without subsidies, as biofuels typically exceed prices. The IEA notes that while technological advancements in efficiency and have reduced conversion costs by up to 50% since 2010, sustained deployment requires policy incentives and infrastructure for non-road sectors like . Feedstock availability poses a further constraint, with projections indicating potential shortages for and renewable diesel by 2027 absent supply chain expansions. Despite optimism in peer-reviewed assessments for net-zero contributions, empirical data underscores that advanced pathways have yet to achieve returns competitive with without external support.

Technological Innovations and Challenges

Recent advancements in biofuel have focused on second- and third-generation feedstocks to overcome limitations of first-generation crops, such as food crop competition. production has seen progress through improved enzymatic and yeast engineering, enabling more efficient of lignocellulosic biomass like agricultural residues. For instance, companies including and GranBio have commercialized facilities processing sugarcane bagasse and other wastes into ethanol, with POET reporting breakthroughs in yield optimization as of 2023. Similarly, in early 2026, EcoCeres reported its new sustainable aviation fuel plant in Malaysia operating near full capacity, and Eni partnered with Q8 to develop a biorefinery in Sicily for advanced biofuels from waste and residues. of yeast strains has enhanced tolerance to inhibitors from pretreatment, boosting titers and reducing costs in biochemical pathways. Algal biofuels represent another innovation avenue, leveraging microalgae's high content and non-arable suitability. Developments include genetic modifications for enhanced accumulation and proprietary cultivation systems, such as BRK Technology's 2025 process converting to drop-in fuels via optimized refinement. The U.S. Department of allocated $20.2 million in 2024 for projects advancing mixed consortia for low-carbon biofuels, emphasizing co-product integration to improve economics. Other techniques, like and for bio- and , have matured, with Fischer-Tropsch synthesis enabling drop-in hydrocarbons compatible with existing infrastructure. Despite these innovations, scalability remains hindered by high capital and operational costs, often exceeding $1 per liter for advanced biofuels compared to $0.50 for conventional . Feedstock logistics, including collection and pretreatment of heterogeneous , contribute significantly to expenses, with enzymatic processes requiring costly cellulases despite yield improvements. Algal systems face challenges in maintaining consistent productivity at scale, compounded by energy-intensive harvesting and , which can negate net gains. Moreover, many demonstration facilities for cellulosic and algal fuels have struggled with commercial viability, as evidenced by historical project delays and bankruptcies, underscoring the gap between laboratory efficiencies and industrial deployment.

Projections for 2030 and Beyond

Global biofuel demand is projected to expand significantly by 2030, with the (IEA) revising its forecast upward to approximately 240 billion liters, reflecting a 50% increase in expected growth from prior estimates, driven by policy mandates and steady fuel needs. In the IEA's Stated Policies Scenario, including biofuels are anticipated to grow by 20% overall, though their share of total energy demand remains below 6%. The Agricultural Outlook forecasts annual consumption growth of 1.7%, propelled by rising demand, priorities, and fiscal incentives in key producing regions. Advanced biofuels, derived from non-food feedstocks such as wastes and residues, are expected to constitute a growing portion of supply, with projected to reach USD 28.76 billion by 2030 at a of 9.3%. The IEA's Net Zero Emissions Scenario envisions biofuel production exceeding 10 exajoules (EJ) by 2030, necessitating 11% annual growth and over 40% reliance on advanced feedstocks to minimize competition with production. However, a persistent feedstock supply gap persists, as current capacities fall short of the volumes required for widespread deployment, compounded by technical hurdles in scaling cellulosic and algal processes. Regional variations highlight uneven progress: in the United States, the (EIA) anticipates modest biofuel production increases through 2050, constrained by market saturation and electrification trends in light-duty vehicles. and maritime sectors may see accelerated uptake, with marine biodiesel demand rising to 1.8 billion liters by 2030 under international regulations. Beyond 2030, the IEA projects potential quadrupling of output by 2035 in accelerated cases, contingent on USD 1.5 trillion in cumulative investments and supply chain enhancements, though historical underperformance relative to targets underscores risks from economic viability and policy inconsistencies. IRENA scenarios suggest biomass demand could double to 108 EJ by 2030 if untapped potentials are realized, but causal factors like land availability and conversion efficiencies limit realism without breakthroughs in yield optimization.

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