Switchgrass harvesting
Jatropha fruits containing the seeds needed to obtain the raw oil
Vertical tubular outdoor photobioreactors

The original version of this article was created by Francesco Gerali, 2020 Elizabeth & Emerson Pugh Scholar in Residence at the IEEE History Center

It is recommended this article be cited as:

F. Gerali (2020). Biofuels, Engineering and Technology History Wiki. [Online] Available:

Fuel whose energy is obtained through a process of biological carbon fixation is defined as a Biofuel. Carbon fixation is a process that takes inorganic carbon and converts it into organic compounds. It can lead to a number of different compounds, like proteins, fats, and alcohols that can be used to provide energy. Any hydrocarbon fuel that is produced from organic matter (living or once living) in a short period of time is considered a biofuel. But biofuel does not have to be made exclusively by a living organism since they are also synthetized through small or mass scale chemical reactions.

While fossil fuels are considered not renewable, because they take millions of years to form, biofuels, can be produced year after year through sustainable farming practices. This implies that biofuels are renewable, but renewable energy is not the same thing as green energy. Renewable means that the source won’t run out and it can be reproduced (e.g. biofuels). A green energy is the one that does not harm ecosystems, contribute to acid rain, or contribute to global warming (e.g. solar). All green energy is considered renewable, but not all renewable energy is green. Biofuels are examples of renewable energy sources that aren’t always green because they produce relevant quantities of greenhouse gases.

Types of Biofuels

Ethanol burns cleaner than gasoline and generates less carbon monoxide, but it produces more ozone than gasoline and contributes substantially to smog levels. In qualitative terms, it has about half the energy per mass of gasoline, which means it takes twice as much ethanol to get the same thermic yield. Last, engines must be modified to run on ethanol.

Biodiesel burns cleaner than diesel, produces less particulate and fewer sulfur compounds. It has slightly less energy than regular diesel and is more corrosive for engine parts than standard diesel, which means engines have to be redesigned to work with biodiesel.

Methanol[1] has about one third/one half as much energy as methane. It is a liquid and easy to transport, while methane is a gas that must be compressed to convoy.

Biobutanol[2] has slightly less energy than gasoline, but it can run in four-strokes engines that uses gasoline without the need for modifications.

Three Generations of Biofuels

Biofuels of first generation are produced directly from the starch, sugar, animal fats, and vegetable oils that alimentary crops can provide - corn, wheat, and sugar cane are the most common first generation feed stock for biofuel. They are used since the 19th century, and production technologies are well rooted. The structure of the biofuel itself does not change between generations, but the source from which the fuel does.

Corn is the primary source of the world's fuel ethanol. Most comes from the United States. In the 2010s, more than 40% of the US corn crop was being used to produce corn ethanol


  • Infrastructure for planting, harvesting, and processing is already in place.
  • Relatively simple conversion of corn starch to ethanol.
  • Potential to use the rest of the plant (stalk, cob, etc.) to produce ethanol as well.
  • There are no indirect land use costs with corn.


  • Relatively high requirement for pesticide and fertilizer, which is expensive and generates soil and water contamination.
  • It is a food staple[3] and use in biofuel has increased food prices worldwide.
  • The production rate is low - just 350 gallons of fuel per acre.
  • Energy yield is about 1.2, which is just barely positive at 20% net yield.

The majority of the world's sugar cane is grown in Brazil, which produces roughly 18 billion litres (5 billion gallons) of fuel ethanol every year. Unlike corn, sugar cane provides sugar rather than starch, which is easier to convert in alcohol. Last, corn requires heating and then fermentation, while sugar cane requires only fermentation.


  • Infrastructure for planting, harvesting, and processing that is already in place.
  • No land use changes provide plantations sizes remain stable.
  • The yield is good, with an average of 650 gallons per acre.
  • Carbon dioxide emissions can be 90% lower than for conventional gasoline – but only in case land use changes do not occur.


  • The average yield is still relatively low
  • Few regions are suitable to cultivation
  • Sugar cane is a food staple in countries of South and Central America
  • Like corn, sugar cane is not considered a viable solution to the world's energy needs. It suits Brazil and a few other countries, but its production cannot be scaled up more.

Soybeans are a global food crop. Despite its relatively high price as a food crop, soybean is still a major feedstock for the production of biofuel. In this case, rather than ethanol, soybean is used to produce biodiesel.


  • Grows in many regions.
  • Relatively easy to maintain.


  • A yield of only about 70 gallons of biodiesel per acre, which is the worst yield of any crop.
  • Soybean is a staple food and thus its use as a biofuel threatens the food chain.
  • It faces a number of disease and pest burdens, requiring pesticides.
  • More energy is usually required to cultivate soybeans than can be derived from the fuel produced from them.

Vegetable oils, which can be derived from any number of vegetables, can fall into the category of first generation biofuel if used directly as virgin vegetable oil.


  • It is easy to convert to biodiesel.
  • It is widely available.
  • It can often be used directly in diesel engines with little modification.


  • It is an important feedstock.
  • When unrefined, it can cause engine damage through carbon deposition due to incomplete combustion.
  • The replacement of old growth forest with oil palms increases carbon emissions and damages biodiversity.

Wheat, sugar beets, rapeseed, peanuts and other food crops have served as feedstock for biofuel. However, they all suffer from the same problems including threatening the food chain, increasing carbon emissions when planted outside traditional agricultural settings, and intense growth requirements. Ultimately, first generation biofuels have given way to second and third generation fuels for the many cons listed previously. First generation will provide biofuels for the close future, but their importance will inevitably diminish.

Biofuels of second generation, named also advanced biofuels are not food crops. The only time the food crops can act as second generation biofuels is if they have already fulfilled their alimentary purpose. For instance, waste vegetable oil is a second generation biofuels because it has already been used and does not longer fit for human consumption. Second generation feedstock is mostly cultivated on what is known as marginal lands[4] that cannot be used for “arable” crops.

Grasses like Switchgrass, Myscanthus, Indiangrass, and others have been placed in the spotlight – with alternate fortune - since the 2000s (Fig.1).


  • They are perennial, there is just a one-time planting cost.
  • They are fast growing and can usually be harvested a few times per year.
  • They have low fertilizer needs.
  • They work well as direct biomass.
  • They have a high net energy yield of about 540%


  • They are not suitable for producing biodiesel.
  • They require extensive processing to obtain ethanol.
  • It may take several years for switchgrass to reach the economic harvest density.
  • They require moist soil; not adapt for arid climates.
  • Water demand is a crucial drawback to grasses and keeps them far from becoming more popular as second generation biofuels.

Jatropha and other seed crops are useful in the production of biodiesel (Fig.2). In the early 2000s, the plant was praised for its yield per seed, which could return values as high as 40%. When compared to the 15% oil found in soybean, Jatropha seemed to be the solution for the future. Unfortunately, it was soon found that oil production drops substantially when Jatropha is grown on marginal land. Similar seed crops had the same disadvantage as Jatropha. Examples include cammelina, and rapeseed. In all cases, the initial benefits of the crops were quickly realized to be offset by the need to use fertile and arable lands to make margins.

Waste Vegetable Oil (WVO) have been used as a fuel for more than a century; some of the earliest diesel engines ran exclusively on vegetable oil.


  • It does not threaten the food chain
  • It is readily available
  • It is easy to convert to biodiesel
  • It can be burned directly in some diesel engines
  • It is low in sulphur
  • There are no associated land use changes


  • It can decrease engine life if not properly refined
  • WVO is probably one of the best sources of biodiesel and, as long as blending is all that is required, can meet much of the demand for biodiesel.

Municipal Solid Waste, which are in many cases simply being allowed to go to waste, are not clean as solar and wind, but the carbon footprint is less than that of traditionally derived fossil fuels. Municipal solid waste is often used in cogeneration plants and burned to produce both heat and electricity.

Differently than first generation biofuels, second generation feedstock are processed using thermochemical conversion, which composes of three separates processes used on the base of the feedstock:

  • Gasification: carbon-based materials are converted to carbon monoxide, hydrogen, and carbon dioxide. This process is different from combustion in that oxygen is limited: the gas that results is named synthesis gas or syngas;
  • Pyrolysis: carried out in the absence of oxygen and often in the presence of an inert gas like halogen. The fuel obtained is converted into two products: tar and char. Wood and a number of other energy crops can be used as feedstock to produce bio-oil through pyrolysis.
  • Torrefaction: very similar to pyrolysis, carried out at lower temperatures. The process often yields better fuels for further use in gasification or combustion; also used to convert biomass feedstock into a form easier to transport.

Another alternative process is the Biochemical Conversion: some biological and chemical processes are adapted for the production of biofuel from second generation feedstock. Fermentation with unique or genetically modified bacteria is adapt for second generation feedstock like landfill gas and municipal waste.

Biofuels of third generation refers to fuels derived from algae. They were considered a second generation biofuels until the late 1980s, when scientists understood their real potential for higher yields with less resource inputs than another feedstock. This convinced the scientific community to set for them a new category. Given the elevated potential to generate biofuels, algae in terms of quantity or diversity is definitely the most effective bio resource currently available. The range of fuels that algae can produce results from two specific characteristics of the microorganism. First, algae produce an oil that can easily be refined into diesel or even into some components of gasoline; second, it can be genetically manipulated to produce ethanol, butanol, gasoline and diesel.

Butanol is of great interest since it is similar to gasoline; it has a nearly identical energy density to gasoline and an improved emissions profile. Until the advent of genetically modified algae, scientists had difficulties to producing butanol. Commercial-scale facilities have been built in some countries and attempting to make of butanol the future substitute for ethanol. Butanol is not only similar in many ways to gasoline, but also does not cause engine damage nor requires engine modifications.

The list of fuels that can be derived from algae includes:

  • Biodiesel
  • Butanol
  • Gasoline
  • Methane
  • Ethanol
  • Vegetable Oil
  • Jet Fuel

Diversity is not the only thing that algae has going for it in terms of fuel potential. It is also capable of producing outstanding yields. In fact, algae have been used to produce up to 9000 gallons of biofuel per acre, which is 10-fold what the best traditional feedstock have been able to generate. Another favorable property of algae is the diversity of ways in which it can be grown.

  • Open ponds: Algae is grown in a pond in the open air, they are simple and have low capital costs but are less efficient than other systems. They are also of concern because other organisms can contaminate the pond and potentially damage or kill the algae.
  • Closed-loop systems:[5] These are similar to open ponds, but they are not exposed to the atmosphere and use a sterile source of carbon dioxide. Such systems have potential because they may be able to be directly connected to carbon dioxide sources and use the gas before is discharged into the atmosphere.
  • Photobioreactors – These are the most advanced and complicated systems to implement, resulting in high capital costs, but their advantages in terms of yield and stability of the process is unparalleled (Fig.3).

The downside with algae resides in the large amounts of water, nitrogen and phosphorus to grow: the production of fertilizer to meet the needs of algae would produce more greenhouse gas emissions than were saved by using algae based biofuel. It also means the cost of algae-base biofuel is much higher than fuel from other sources. This single disadvantage means that the large-scale implementation of algae to produce biofuel will not be implemented shortly. Back in 2013, after investing more than $600 million into research and development of algae, Exxon Mobil concluded that algae-based biofuels will not be viable until 2040s.

Structural limits of biofuels as source of energy

Cost, availability, and food supply are the three main interrelated factors in the balance between the global utilization of biofuel and fossil fuel use around the world. It was thought that biofuels could be produced in limitless quantity because they are renewable. But, to meet the global energy demand with biofuels it would be necessary to detract precious land from the process of growing food. As the population grows, our demands for both energy and food grow: there is not enough land to grow biofuel and food and meet the needs.

The balance between food and biofuel is what keeps the relatively simple process of growing and making biofuels from being enough cheaper than fossil fuel. Furthermore, this factor is combined with the increased ability to produce petroleum and gas from the ground. The result is that in the history of fuel pricing, the price of fossil fuel has been always lower than that of biofuel.

Biofuels and Biodiversity

Biodiversity[6] refers to the variety of different living things in an environment. Growing a single type of corn is easier for producing biofuels because scientists can select the better variety capable to yield the best raw product easier and cheaper to grow. The problem is that pests that eat the selected type of corn will begin to proliferate exponentially. The massive spraying of pesticide to kill these pests, will make them more resistant to the pesticide itself. Over time, these pests will grow in number and totally immune to ordinary chemical defenses used in agriculture.

Biodiversity is important to ensuring that pests do not grow out of control; but, the current “state of the art” of the farming practices needed to produce large quantities of biofuels does not find compatibility with biodiversity.

Glossary of Biofuels Science and Technology


Acid hydrolysis:[7] A chemical reaction in which acid is used to convert starch or cellulose to sugar. It is often the first step in ethanol production.

ADM Hamburg AG: A division of ADM based in Germany that focuses on the production of biodiesel from rapeseed and grain.

Advanced biofuel (or second generation biofuels): Any biofuel produced from a sustainable feedstock that does not threaten the food supply.

Aviation Grade Ethanol 85 (AGE 85): Aviation fuel containing 85% ethanol and 15% biodiesel that can be used in piston engine aircraft. Abbreviation for

Alcohol: Any organic compound that contains an oxygen single-bonded to a hydrogen atom (OH group).

Algae:[8] A group of diverse, generally autotrophic organisms that can be either single-cell or multi-cell. Various species of algae are used to produce ethanol and butanol.

Algenol: A United States biofuel company that produces ethanol directly from algae without harvesting them.

Anaerobic digestion: Breakdown of organic matter in an environment where oxygen is NOT present, which produces methane and CO2.

Aromatics: Any hydrocarbon that contains a ring (usually six carbon atoms) in which the carbon atoms all share electrons equally, resulting in bonds with characteristics that are intermediate between single and double bonds. Bonds are considered to be unsaturated.

Australian Biofuels Research Institute (ABRI):[9] An organization funded by the federal government of Australia with the goal of developing biofuel research


B100: Biodiesel that contains no petroleum products. It is 100% renewable, organic biodiesel. Requires extensive engine modifications. VW produces B100 compatible vehicles. Prone to low-temperature gelling.

B2: A mixture of 2% biodiesel to 98% petrodiesel

B20: A mixture of 20% biodiesel to 90% petrodiesel

B5: A mixture of 5% biodiesel to 95% petrodiesel. A common blend in the UK.

Bagasse: The dry, fibrous remnants of sugarcane or sorghum once the sugar has been extracted. It contains mostly cellulose, hemicelluloses, and lignin. It can be burned directly to generate electricity or converted to ethanol.

Biobutanol: Butanol produced from biomass. It can be used in unmodified gasoline engines.

Biodiesel: Diesel fuel produced from biomass. Biodiesel cannot be used in standard engines without modification as it corrodes rubber seals and gaskets. It also has a lower gelling point than petrodiesel, making it unsuitable for use in colder climates. Biodiesel is often blended with petrodiesel.

Biodiversity: The amount of variation in an ecosystem. Greater variation indicates a healthier ecosystem. Genetically modified organisms and large monocultures used in biofuel production can threaten biodiversity.

Bioenergy: Any renewable energy made from biological sources. Fossil fuels are not counted because, even though they were once biological, they are long dead and have undergone extensive modification.

Biofuel: Any fuel derived from biological carbon fixation, including solid fuels, bioethanol and other bioalcohols, biodiesel, etc. Biogas: A mixture of methane and CO2 with water vapor created by the breakdown of organic matter in the presence of oxygen.

Biohydrogen: Hydrogen that is produced biologically (most often by bacteria and algae).

Bioreactor: Any device that supports a biologically active environment. In the context of biofuels, a bioreactor is most often used to grow algae.

Black liquor: Used cooking liquor from the kraft process for producing paper. It contains lignin, hemicelluloses, and other wood extracts. It is considered a waste product and can be gasified to produce biofuel.

Blue Marble Biomatierals: A U.S. biofuel company that produces biofuel and biochemicals from various feedstock.

British Thermal Unit (BTU): A measure of heat that is equivalent to the amount of energy required to raise the temperature of 1 pound of water by 1 degree Fahrenheit.

Brown liquor: Similar to black liquor, but it is derived from the sulfite process of paper production. Alternatively called red liquor, thick liquor, and sulfite liquor.

Butanol: A six-carbon alcohol that is more similar to gasoline than ethanol. It can be used in gasoline engines without the need for modification and produces roughly that same amount of energy per mass as gasoline.


Camelina: A genus of flowering plant related to flax. Some species produce seeds with large quantities of oil that can be converted to various biofuels (e.g. biodiesel). Camelina grows well in moderate climates.

Carbon dioxide: A molecule made of one carbon atom double bonded to two oxygen atoms (one of each side of the carbon). It is a colorless, odorless gas at standard temperature and pressure and is widely implicated as one of the major causal agents in greenhouse warming.

Carbon monoxide: A molecule made of one carbon atom bonded to a single oxygen atom via a triple bond. It is a product of inefficient combustion of hydrocarbon compounds. It is a pollutant and is toxic to humans at concentrations above 50 ppm during long term exposure, or 667 ppm during short term exposure.

Carbon Negative: A product or process that, over its entire lifetime, causes a net decrease in atmospheric carbon levels.

Carbon Neutral: A product or process that, over its entire lifetime, causes no net increase or decrease in atmospheric carbon levels.

Carbon Positive: A product or process that, over its entire lifetime, causes a net increase in atmospheric carbon levels.

Carbon sink: Any reservoir that can accumulate or store carbon-containing compounds for a prolonged or indefinite period. This is particularly relevant to carbon dioxide, which could be stored to reduce its environmental impact.

Cassava: A woody, tropical shrub well known for being the source of tapioca extract. It is used in southeast Asai for the production of biodiesel and ethanol.

Cellulose: An organic polysaccharide of the general formula (C6H10O5)n that is the structural component of the cell wall of most green plants. It is used in several biofuel production processes. Biofuel produced primarily from cellulose is sometimes called cellulosic biofuel.

Cellulosic Ethanol: Ethanol produced from the inedible, cellulose-rich parts of plants. Studies are conflicting on its benefits, but he U.S. Department of Energy has suggested it can reduce greenhouse gas emissions by as much as eighty-five percent over reformulated gasoline.

Cetane Rating: A number used to rate the quality of diesel fuel or any fuel combusted via compression ignition. Petro diesel ranges from cetane 40-55 in most cases while biodiesel ranges from 46-52 if plant-based and 56-60 if animal based

Chaff: The protective casings of seeds of many grains, cereals, and straw. Some livestock can consume it, but it is generally considered to be a waste product.

Charcoal: A residue consisting of amorphous carbon that is obtained by pyrolysis or burning of wood or other organic compounds. It is used in the production of syngas.

Chemrec: A company based in Stockholm, Sweden that specializes in the conversion of black and brown liquors to syngas.

Cloud Point: The temperature at which solids dissolved in al liquid are no longer completely soluble and begin to precipitate. Biodiesel often reaches a cloud point at higher temperatures than petrodiesel, making it less suitable for cold environments. This is one measure of the quality of diesel fuel or aviation fuel.

Cogeneration (Combined Heat and Power): The production of electric energy along with a second for of energy (often heat).

Combustion (Burning): The process by which a fuel and an oxidant react to product heat (energy) and other compounds (CO2 and H2O in ideal hydrocarbon combustion)

Combustion Gases: The gases released during a combustion process. Similar to emissions.

Compression-ignition engine: An internal combustion engine in which the fuel is ignited by heat generated from compressing the gas to high pressures rather than from a spark. Most diesel engines work this way.

Corn (Maize): A domesticated grain grown widely throughout the world. Corn is the largest source of ethanol feedstock in the world.

Cunninghamella Japonica: A type of tropical fungus recently found to produce hydrocarbons from organic matter. The hydrocarbons indistinguishable from those found in fossil fuels.


Denatured Ethanol: Ethanol that has additives to make it undrinkable. It is commonly used as a fuel and in chemical applications.

Diester: The French term for biodiesel. It is a contraction of the words diesel and ester.

Diester Industrie: A subsidiary of the French petroleum company Diester Industrie International that specializes in the production of biodiesel

Dimethylfuran: A heterocyclic compound that can be used as a biofuel. It is easier to produce than butanol and has an energy content 40% greater than ethanol.

Direct Land Use Changes: Refers to changes in the way humans impact a given area of the earth and how that change affects greenhouse gas emissions. Attention is given to water diversion, biodiversity, and limited energy investment costs.

Distiller’s Wet Grains (DWG): Grains containing more than 12% water and often up to 70% water.

Dried Distillers Grains (DDG): Unfermented grain residues that have been dried so as to extend the shelf life.

Dried Distillers Grains with Solubles (DDGS): Unfermented grain residues that have been dried to 10-12% moisture so as to extend shelf life. Commonly used in ethanol production

Dry milling: Mechanical grinding of a feedstock that does not use water.

Dryer: Apparatus that removes water from distiller’s wet grains to produce distiller’s dried grains.

DuPont Danisco: A joint venture between DuPont and Danisco foods to produce cellulosic ethanol using sugarcane, corn, and switchgrass.


E10: Blend of 10% ethanol and 90% gasoline.

E100: 100% fuel ethanol. Used mainly in Brazil.

E2: A blend of 2% ethanol and 98% gasoline.

E85: A blend of 85% ethanol and 15% gasoline, which is the common blend implied by the term flex fuel vehicle (FFV). Generally seen only in the Brazil and the Midwestern United States.

E90: A blend of 90% ethanol and 10% gasoline.

Emissions: The gaseous or particulate components expelled during a combustion reaction. The term commonly refers to the mix of gases and particulate that exit the exhaust of an internal combustion engine.

Energy Balance: In regard to biofuel, this term refers to the amount of energy required to produce the fuel versus the amount of energy derived from the fuel.

Energy Content: Also referred to as heating value, energy content is a measure of the number of British Thermal Units obtained by burning a set volume of fuel. Because it relies on volume, energy content can change with temperature and pressure.

Energy Crop: A low-cost, low maintenance plant gown exclusively for use as fuel.

Energy Density: Generally, the amount of energy stored in a given region of space per unit volume. Specifically, the amount of energy obtained from a specified mass of biofuel. Useful for comparing various types of biofuels in a standardized manner.

Energy Efficiency Ratio: A comparison of the energy stored in a fuel and the energy needed to produce, transport, and distribute the fuel.

Enzyme: A biological molecule that performs chemical interconversions. I.E., a molecule from a living organism that converts one chemical into another.

Ethanol (Grain Alcohol): An alcohol composed of two carbons. The formula is C2H4O

Ether: A class of organic compounds that contains an ether group defined as R-O-R’ where R is any hydrocarbon chain and R’ is another hydrocarbon chain. Ethers are under consideration as biofuels and are used as additives in current fossil fuel blends

Ethyl Tertiary Buytl Ether (ETBE): Ether commonly used to oxygenate gasoline. Ether provides for cleaner combustion and decreased emissions.


FAME biodiesel: Fatty Acid Methyl Ester biodiesel

Feedstock: The raw material from which a biofuel is produced. Feedstock is generally a plant itself, but in the case of algae, the feedstock is any source of carbon (often carbon dioxide)

Fermentation: A normal metabolic process in which oxygen is NOT the final electron acceptor. Fermentation is the process through which alcohols are made.

First generation biofuel: Any biofuel derived from sugar, starch, or vegetable oil. In general, these fuels are considered a threat to food supply chains.

Flashpoint: The lowest temperature at which a flammable liquid produces enough vapor to ignite. For most flammable liquids like gasoline, it is the vapor and not the liquid itself that is combustible.

Flexible Fuel Vehicle (FFV): A vehicle with an internal combustion engine that can run on more than one fuel. Usually the vehicle is designed to run on pure gasoline or a defined blend of gasoline/ethanol or gasoline/methanol. In some cases, the vehicle can run on pure ethanol.

Fungi: One of the kingdoms of living organisms. Fungi are eukaryotic organisms that are similar to plants in many ways, but which are not able to perform photosynthesis. Yeast, mold, and mushrooms are all fungi.


Gas to liquid: A refinery process that takes gaseous hydrocarbons like natural gas and converts them into longer hydrocarbons that are liquids. Methane and syngas are commonly converted to liquid fuels.

Gasification: The conversion of carbonaceous solids into carbon monoxide, hydrogen, and carbon dioxide gases. This usually takes place at high temperatures and in the presence of steam.

Gasohol: Blends that are between E5 and E25 are commonly referred to as gasohol in the United States. The E10 blend is most commonly called gasohol throughout the rest of the world.

Gel point: The temperature at which an infinite polymer network is formed. Sometimes this term is used interchangeably with cloud point, but the meaning is different. At cloud point, solute precipitates (comes out of) from the solution whereas at gel point, the components of the substance form polymer chains long enough to make the substance solid rather than liquid. Gel point is also defined as the point that a liquid fuel takes on the consistency of petroleum jelly.

Genetically modified organism (GMO): A living thing that has had its genetic material (either DNA or RNA) manipulated by humans using recombinant techniques. The direct modification of DNA through an artificial process. Gevo: A U.S. company that creates “renewable chemicals” and isobutanol using genetically modified microorganisms.

Gliocladium roseum: A fungus from Patagonia that produces diesel fuel from cellulose.

Glucose: The sugar most commonly produced by living organisms.

Glycerine (Glycerol): A simple compound mad of three carbons and three OH (hydroxyl) groups. It is a component of fatty acids and, as a result, a byproduct of biodiesel production via transesterification.

Greenhouse Effect: The warming of the Earth as a result of heat that is trapped by certain gases.

Greenhouse Gas: Any gas that traps heat in the Earth’s atmosphere and thus leads to increased temperatures. Water vapor, carbon dioxide, methane, ozone, chlorofluorocarbons, and nitrous oxide are all greenhouse gases.

Gushan Environemental Energy: A Chinese biodiesel and glycerol producer that uses vegetable oil and used cooking oil for feedstock.


Hydrocarbon: A compound that consists solely of hydrogen and carbon atoms. Most fossil fuels are hydrocarbons.

Hydrogen sulfide: A poisonous, foul-smelling (rotten eggs) gas mde up of two hydrogen atoms and one sulfur atom. It is often found along with petroleum deposits and is considered a contaminant in fossil fuels.

Indirect Land Use Changes: Changes to land as a result of growing biofuel feedstock that are not a direct result of human intervention. This can include loss of biodiversity, subsequent changes to the ecosystem that have broader impact, and more. Essentially, this refers to the unintended consequences of releasing more CO2 by using land for biofuel feedstock growth. Abbreviated ILUC.

International Energy Agency (IEA) Bioenergy: A subdivision of the IEA working to achieve global integration of substantial bioenergy use.


Jatro BioJet Fuel: A German company focusing on the production of Jet Fuel from Jatropha. The company produces certified Jet A-1 fuel, which has been using in several test flights and is set to be purchased by several major airlines in the coming years.

Jatropha: A genus of flowering plants that grown in tropic regions, on marginal land. Oil from Jatropha seeds can be used to produce biodiesel.

Jilin Fuel Ethanol: A Chinese bioethanol company that operates the largest bioethanol plant in the world.

Joule: A measure of energy or work defined as the energy expended by applying a force of one newton over a distance of one meter.

Joule Unlimited: A U.S. biofuel company that focuses on the production of ethanol and biodiesel using genetically modified algae.

Jugian Zhongde Energy Co: A Chinese Energy company that produces ethanol.

Knock: A pinging sound that occurs in internal combustion engines when fuel is burned at the incorrect time. This often occurs because the fuel either burns too quickly, too slowly, or too early in the cycle. Fuels with a low octane rating are more prone to detonate early or burn too long.


Landfill Gas: Biogas (methane, CO2, and water vapor) produced from the breakdown of organic material in landfills.

Lifecycle analysis: Determining the environmental impact of all stages of an activity starting with raw material extraction through production, use, and disposal.

Lignin: A complex chemical found mostly in woody plants and some algae.

Lignocellulose: A group of substances that make up the plant walls of woody plants and which consist of a mixture of cellulose and lignin.

LS9 Inc.: A U.S. company that produce biofuels from genetically modified organisms, primarily algae.

Lubricity: A measure of how well a lubricant reduces friction. Also referred to as a lubricant’s “anti-wear property.”


M85: A mixture of 85% methanol and 15% gasoline. It is relatively uncommon given the low energy density and high toxicity of methanol.

Mash: A mixture of grain and water that is used as the base for fermenting ethanol.

Megajoule: 1,000,000 joules. A common measure of energy in fuels.

Methanol: Also called wood alcohol. Methanol is composed of a single carbon, one oxygen, and four hydrogen molecules. It is highly toxic and has a relatively low energy density.

Methyl Ester: The primary component of biodiesel, created by adding methanol to a fatty acid to produce three methyl esters and a glycerol molecule.

Methyl Tertiary Butyl Ether (MTBE): A common gasoline additive used to raise octane and thus reduce knock. It is used to oxygenate gasoline.

Multifeedstock: A technology that is able to produce fuel or energy from more than one type of feedstock.


National Fuel Alcohol Program: Also called the Programma Nactional do Alcool in Brazil, this was the national policy of the country of Brazil that set standards for the inclusion of ethanol in fuel. As a result of this program, Brazil became the global leader in ethanol-based fuels.

National Renewable Energy Laboratory (NREL):[10] The scientific arm of the U.S. government tasked with research and development of alternative energy technology.

Neat Fuel: Any fuel that is pure or unmixed.

Nitrogen: Nitrogen is the name of both an element and a molecule. Molecular nitrogen is a colorless, odorless gas made up of two nitrogen atoms covalently bonded to one another. Under the high temperatures and pressures of combustion, nitrogen can combine with other compounds to form nitrogen oxides, which are considered pollutants.

Nitrogen oxides: A group of compounds containing oxygen and nitrogen in varying ratios. NO and NO2, generically referred to as NOx, are produced during high temperature combustion and contribute to the production of acid rain and ozone.

Novozymes: A biotech company headquartered in Denmark that produces enzymes and microorganisms for various industries, including biofuels.


Octane: A collection of hydrocarbons of the formula C8H12 that are components of gasoline. Pure isooctane, one of the structural isomers of octane, is used as the reference for rating the anti-knock qualities of gasoline.

Octane Rating: A way of rating the performance of motor and aviation fuels. Higher octane numbers indicate the ability of a fuel to withstand greater compression without detonation (burning). Higher compression generally means higher engine performance.

Organization for Economic Cooperation and Development (OECD):[11] An international association of 34 countries that work to improve the economic situation of all people on the planet. Part of their focus includes holding down the costs of energy and so they have a lot of input regarding biofuel policy.


Palm oil: An edible vegetable oil derived from oil palm trees. Palm oil is used to produce biodiesel.

Particulate: A small quantity of solid or liquid that is dispersed within a gaseous (or liquid) emission. Dust, smoke, soot, aerosols, and sprays are all particulates.

Photobioreactor: A device that supports a biologically active environment that incorporates a light source to provide energy. Often used in the growth of algae.

Photosynthesis: The process by which living organisms like plants and algae convert light energy into chemical energy.

Proof: In reference to ethanol, a proof is equivalent to 0.5% by volume. For example, a 30 proof alcoholic beverage would be 15% alcohol by volume.


Rapeseed: A flowering member of the mustard/cabbage family that grows in temperate climates.

Reformulated gasoline (RFG): Gasoline blended to burn more cleanly and to reduce smog and other toxins from entering the air. Reformulated gasoline contains MTBE, ETBE, or an alcohol to add oxygen for improved combustion.

Renewable Diesel (Green diesel): Any diesel fuel that is produced from a renewable source. Renewable diesel does not have to be environmentally friendly or reduce GHG emissions.

Renewable Fuels Standard (RFS): The U.S. policy governing the minimum amount of renewable fuel in transportation fuel.


SG Biofuels: A U.S. biofuel company that focuses on molecular breeding and biotechnology to produce hybrid varieties of Jatropha.

Solazyme: A U.S. biofuel company that produces algal fuel for use in ground and air application. The company also produces personal care and nutritional products derived from algae.

Solid Biofuel: Any solid biomass including wood, sawdust, grass trimmings, charcoal, agricultural waste, and dried manure.

Soybean: A type of legume native to Asia that is used primarily as a food, but which also has limited application in biofuel production.

Starch: A polymer of glucose molecules that is made by plants. Starch must be converted to sugar (individual glucose molecules) before it can be fermented to produce alcohol.

Stover: The dried stalks and leaves of a crop after the edible parts have been harvested.

Sugarcane: Any of 37 species of perennial grass rich in sugar and native to warm tropical regions.

Switchgrass: A perennial grass native to North America that is considered as a potential fuel for the production electricity via direct combustion.


Thermal Conversion: The transformation of complex organic material into light crude oil using pressure and heat.

Transesterification: The process of exchanging the organic group of an ester with the organic group of an alcohol. The process is used to produce biodiesel from triglyceride.

Triglyceride: Organic compounds composed of three fatty acid chains connected to a glycerol molecule.


Vegetable Oil: A triglyceride extracted from a plant.

Viscosity: A measure of the resistance of a fluid to deformation by shear stress or tensile stress. Viscosity is an important component of lubricating oils.

Volatility: A measure how easily a liquid is converted to a gas. The lower the temperature at which a liquid evaporates, the more volatile it is considered to be.


Waste Vegetable Oil (WVO): Vegetable oil that is no longer fit for use in food.

Wet milling: A process in which feedstock is steeped in water to soften it before it is ground.

See also


Agarwal S., Kumar A. 2018. “Historical Development of Biofuels”. In: Kumar A., Ogita S., Yau YY. (eds) Biofuels: Greenhouse Gas Mitigation and Global Warming. Springer, New Delhi.

Carlo R Carere, Richard Sparling, Nazim Cicek, David B Levin. 2008. “Third-generation biofuels via direct cellulose fermentation”. International Journal of Molecular Sciences 9: 1342: 1360.

Carraretto C. Macor A. Mirandola A., Stoppato, A., & Tonon, S.2004.“Biodiesel as Alternative Fuel: Experimental Analysisand Energetic Evaluations”. Energy 29: 2195–2211.

Committee on Economic and Environmental Impacts of Increasing Biofuels Production; National Research Council (U.S.). Board on Agriculture and Natural Resources Division on Earth and Life Studies; National Research Council (U.S.). Board on Energy and Environmental Systems, Division on Engineering and Physical Sciences. 2011. Renewable fuel standard: potential economic and environmental effects of U.S. biofuel policy. Washington, D.C.: National Academies Press.

Dwivedi, G., S. Jain, and M. P. Sharma.2011.“Impact of Biodiesel and Its Blends with Diesel and Methanol onEngine Performance.” International Journal of Energy Science 1 (2): 105–109.

Guo, Mingxin, Weiping Song, Jeremy Buhain. “Bioenergy and biofuels: History, status, and perspective”. Renewable and Sustainable Energy Reviews, Volume 42, 2015, Pages 712-725.

Hine, Robert, ed. 2015. A Dictionary of Biology. Seventh ed. Oxford, United Kingdom: Oxford University Press.

Kaltschmitt, Martin. Energy from Organic Materials (Biomass). A Volume in the Encyclopedia of Sustainability Science and Technology, Second Edition. Springer, New York, NY.

Knothe, G. 2012. “Historical Perspectives on Biofuels”. Comprehensive Renewable Energy 5: 11-14

Larkin, Robbie, McCartney, David. 2015. Encyclopedia of Alternative and Renewable Energy: Volume 14 (Liquid Biofuels). New Delhi, ML Books International.

Lawrence, Eleanor. 2016. Henderson's Dictionary of Biology. Sixteenth ed. Harlow, England: Pearson Education.

Paladino, Ombretta, Neviani, Matteo. 2017. “A closed loop biowaste to biofuel integrated process fed with waste frying oil, organic waste and algal biomass: Feasibility at pilot scale”. Renewable Energy 124: 1-29.

Rafael Luque James Clark. Handbook of Biofuels Production - Processes and Technologies. Cambridge: Woodhead Publishing.

Ragauskas, Arthur J. 2014. Materials for biofuels. World Scientific series in materials and energy, volume 4. Hackensack, New Jersey: World Scientific.

Songstad, D. D., P. Lakshmanan, J. Chen, W. Gibbons, S. Hughes and R. Nelson. 2009. “Historical Perspective of Biofuels: Learning from the Past to Rediscover the Future”. Vitro Cellular & Developmental Biology 45, No. 3: 189-192.

Wexler, Philip. 2014. Encyclopedia of Toxicology. Amsterdam: Elsevier.

Further Reading