Glossary of Bioenergy Terms

Oklahoma NSF EPSCoR Research

A - B

Anaerobic digestion: Degradation of organic matter by microbes in the absence of oxygen to produce methane and carbon dioxide. (source: National Renewable Energy Laboratory)

Bagasse: Residue remaining after extracting a sugar-containing juice from plants like sugar cane. (source: National Renewable Energy Laboratory)

Biobased product: Any product such as fuels, chemicals, building materials, electric power or heat that can be industrially produced from biomass. (source: Sun Grant BioWeb)

Biobutanol: Butanol or butyl alcohol is a primary alcohol with a 4 carbon structure and the molecular formula of C4H10O. It is primarily used as a solvent, as an intermediate in chemical synthesis, and as a fuel. It is of particular interest because it lends itself to production from abundant cellulose resources such as switchgrass, crop residues, and woodchips. Butanol produced from cellulose and other biomass is distinguished as biobutanol. The energy characteristics of butanol are similar to gasoline, and it can achieve fuel mileage similar to gasoline in today's combustion engines without vehicle modifications. (source: Sun Grant BioWeb)

Biochemical conversion:The use of fermentation or anaerobic digestion to produce fuels and chemicals from organic sources (source: Biomass Energy Data Book)

Biodiesel: Biodiesel is a renewable, biodegradable fuel derived from agricultural plant oils or animal fats. It can be used alone or blended with petroleum diesel fuel in diesel engines. Biodiesel blends must be at least 2% biodiesel and are identified by the percentage of biodiesel in the blend. B2, B5, B10 and B99 are the principal biodiesel blends used in the U.S. today. (source: Sun Grant BioWeb)

Bioenergy: Energy forms derived from the production, conversion, and use of material directly or indirectly produced by photosynthesis (including organic waste) to manufacture fuels and substitutes for petrochemical and other energy-intensive products. (source: National Renewable Energy Laboratory)

Bioethanol: Ethanol produced from biomass. (source: ASABE terms update)

Biofuel: A fuel derived from biomass. (source: ASABE terms update)

Biogas: A gaseous mixture of carbon dioxide and methane produced by the anaerobic digestion of organic matter. (source: National Renewable Energy Laboratory)

Bioheat: Heat energy generated from biomass sources. (source: ASABE terms update)

Biomass: Any organic matter that is available on a renewable basis, including agricultural crops, agricultural wastes and residues, wood and wood wastes and residues, animal wastes, municipal wastes, and aquatic plants. (source: Sun Grant BioWeb)

Biomass energy: Energy produced by the conversion of biomass directly to heat, or to a liquid or gas that can be converted to energy. (source: Sun Grant BioWeb)

Biomass fuel: Biomass converted directly to energy, or converted to liquid or gaseous fuels such as ethanol, methanol, methane, and hydrogen. (source: Sun Grant BioWeb)

Bio-oil: A product of pyrolysis or liquefaction of biomass. It is a dark brown, partially water miscible liquid which contains oxygenated organic compounds. (source: ASABE terms update)

Biopower: Electricity from biomass or intermediate bioproducts. (source: ASABE terms update)

Biorefinery: A facility that processes and converts biomass into value-added products. These products can range from biomaterials to fuels such as ethanol or important feedstocks for the production of chemicals and other materials. Biorefineries can be based on a number of processing platforms using mechanical, thermal, chemical, and biochemical processes. (source: Biomass Energy Data Book)

Butanol: Butanol or butyl alcohol is a primary alcohol with a 4 carbon structure and the molecular formula of C4H10O. It is primarily used as a solvent, as an intermediate in chemical synthesis, and as a fuel. It is of particular interest because it lends itself to production from abundant cellulose resources such as switchgrass, crop residues, and woodchips. Butanol produced from cellulose and other biomass is distinguished as biobutanol. The energy characteristics of butanol are similar to gasoline, and it can achieve fuel mileage similar to gasoline in today's combustion engines without vehicle modifications. (source: Sun Grant BioWeb)

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C - F

Carbon Cycle: The carbon cycle includes the uptake of carbon dioxide by plants through photosynthesis, its ingestion by animals and its release to the atmosphere through respiration and decay of organic materials. Human activities like the burning of fossil fuels contribute to the release of carbon dioxide in the atmosphere. (source: Biomass Energy Data Book)

Carbonization: The conversion of organic material into carbon or a carbon-containing residue through pyrolysis. (source: Biomass Energy Data Book)

Catalyst: : A substance that increases the rate of a chemical reaction without being consumed or produced by the reaction. Enzymes are biocatalysts for many biochemical reactions. (source: National Renewable Energy Laboratory)

Cellulase: A family of enzymes that break down cellulose into glucose molecules. (source: National Renewable Energy Laboratory)

Cellulose: The carbohydrate that is the principal constituent of wood and other biomass and forms the structural framework of the wood cells. It is a polymer of glucose with a repeating unit of C6H10O5 strung together by ß-glycosidic linkages. The ß-linkages in cellulose form linear chains that are highly stable and resistant to chemical attack because of the high degree of hydrogen bonding that can occur between chains of cellulose (see below). Hydrogen bonding between cellulose chains makes the polymers more rigid, inhibiting the flexing of the molecules that must occur in the hydrolytic breaking of the glycosidic linkages. Hydrolysis can reduce cellulose to a cellobiose repeating unit, C12H22O11, and ultimately to glucose, C6H12O6. Heating values for cellulose may be slightly different based upon the feedstock. Example values are shown below (higher heating value [HHV] at 30°C, dry basis). (Source: Domalski, E.S.; Milne T.A., ed. Thermodynamic Data for Biomass Materials and Waste Components. The ASME Research Committee on Industrial and Municipal Wastes, New York: The American Society of Mechanical Engineers, 1987)

cotton linters: HHV=7497 BTU/LB (4172.0 cal/g, 17426.4 J/g) wood pulp: HHV=7509.6 BTU/LB (4165.0 cal/g, 17455.6 J/g) (source: National Renewable Energy Laboratory)

Cellulosic biomass feedstock: Any cellulosic matter such as crops, grasses, short-rotation trees, wheat straw, corn stover, wood pulp, or other organic matter grown for the express purpose of producing energy. (source: National Renewable Energy Laboratory)

Char: A residue resulting from pyrolysis, carbonization, and gasification of biomass. (source: ASABE terms update)

Co-Firing: The simultaneous use of two or more different fuels in the same combustion chamber of a power plant. Generally refers to co-burning coal and biomass. (source: ASABE terms update)

Co-Gasification: The simultaneous use of coal and treated/ untreated biomass in the gasification process to produce syngas. (source: ASABE terms update)

Combined bioheat and power: Bioheat and biopower simultaneous generated from biomass sources. (source: ASABE terms update)

Combustion: Rapid oxidation, with the release of energy in the form of heat and light. (source: Sun Grant BioWeb)

Dedicated energy crop: A dedicated energy crop is an agricultural crop that has been planted for the specific purpose of serving as a feedstock for bioenergy production. There are a large number of crops that may potentially be grown as dedicated energy crops in the U.S., including various grasses such as switchgrass and fast growing trees such as poplars and willows, among others. (source: Sun Grant BioWeb)

Distillers Dried Grains (DDG): The dried grain byproduct of the grain fermentation process, which may be used as a high-protein animal feed. (source: National Renewable Energy Laboratory)

Distillers Wet Grains (DWG): is the product obtained after the removal of ethyl alcohol by distillation from the yeast fermentation of corn. (source: Biomass Energy Data Book)

Drop-in fuel or Infrastructure compatible fuel: Synthetic gasoline or diesel or jet fuel prepared from biomass that is completely interchangeable or compatible with the conventional fuels. (source: ASABE terms update)

Energy Crop: A crop grown specifically for its fuel value. These include food crops such as corn and sugarcane, and nonfood crops such as poplar trees and switchgrass. (source: Sun Grant BioWeb)

Ethanol: A colorless volatile flammable liquid, C2H5OH, widely used in industrial processes, as a solvent, as a fuel, and in alcoholic beverages. In the United States, ethanol is used as a gasoline octane enhancer in maximum 10 percent concentration, and in higher concentrations in vehicles designed for its use. In the U.S., terms for ethanol usually reflect the percentage of ethanol blended with petroleum-derived gasoline. For example, E10 is 10% ethanol blended with 90% gasoline, and E85 is 85% ethanol blended with 15% gasoline. Ethanol can be produced chemically from ethylene, or biologically from fermentation of agricultural crops and cellulosic residues from crops or wood. (source: Sun Grant BioWeb)

Fast pyrolysis: Pyrolysis in which reaction times are short, resulting in higher yields of certain fuel products, which may range from primary oils to olefins and aromatics depending on the severity of conditions. (source: National Renewable Energy Laboratory)

Feedstocks: Any biomass resource destined for conversion to energy, or to another form such as fuel or bioproducts. For example, corn is a feedstock for ethanol production. Soybean oil may be a feedstock for biodiesel, or a feedstock for bioproducts such as inks, paints, coatings and other bioproducts. Cellulosic biomass has potential to be a significant feedstock source for biofuels, biopower, and bioproducts. (source: Sun Grant BioWeb)

Fermentation: A biochemical reaction that breaks down complex organic molecules (such as carbohydrates) into simpler materials (such as ethanol, carbon dioxide, and water). Bacteria or yeasts can ferment sugars to ethanol. (source: National Renewable Energy Laboratory)

Fiber products: Products derived from fibers of herbaceous and woody plant materials. Examples include pulp, composition board products, and wood chips for export. (source: Biomass Energy Data Book)

Forage crops: Annual or perennial crops such as hay, grown primarily to provide feed for livestock. During harvesting operations, most of the above ground portion of the plant is removed from the field and processed for storage and later feeding. (source: Sun Grant BioWeb)

Fossil fuel: Fuels such as oil, natural gas and coal formed in the ground over millions of years by chemical and physical changes in plant and animal residues under high temperature and pressure. (source: ASABE terms update)

Fouling: The coating of heat transfer surfaces in heat exchangers such as boiler tubes caused by deposition of ash particles. (source: Biomass Energy Data Book)

Fuel cell: A device that converts the energy of a fuel directly to electricity and heat, without combustion. (source: Biomass Energy Data Book)

Fuel cycle: The series of steps required to produce electricity. The fuel cycle includes mining or otherwise acquiring the raw fuel source, processing and cleaning the fuel, transport, electricity generation, waste management and plant decommissioning. (source: Biomass Energy Data Book)

Fungible fuels: Fuels such as ethanol, butanol etc. made from biomass which has chemical similarities with conventional fuels such as gasoline and can be blended and used in the existing engines. (source: ASABE terms update)

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G - M

Gasification: The high temperature process to decompose the complex hydrocarbons of biomass into simpler gaseous molecules, primarily hydrogen, carbon monoxide, and carbon dioxide. Some char, mineral ash, and tars are also formed, along with methane, ethane, water, and other constituents. The product gas must be cleaned of solids, tars, and other contaminants sufficient for the intended use. The mixture of raw product gases vary according to the feedstock and gasification approach. (source: Wisconsin Biorefining Development Initiative)

Gasifier: A device which converts hydrocarbon feedstock into gaseous components via thermochemical process. (source: U.S. Department of Energy)

Gasohol: A mixture of 10% anhydrous ethanol and 90% gasoline by volume; 7.5% anhydrous ethanol and 92.5% gasoline by volume; or 5.5% anhydrous ethanol and 94.5% gasoline by volume. There are other fuels that contain methanol and gasoline, but these fuels are not referred to as gasohol. (source: Biomass Energy Data Book)

Gas turbine: (combustion turbine) A turbine that converts the energy of hot compressed gases (produced by burning fuel in compressed air) into mechanical power. Often fired by natural gas or fuel oil. (source: Biomass Energy Data Book)

Genetic selection: Selection procedures to systematically improve a population by changing the frequency of genes for target traits.

Glucose: (C6H12O6) A simple six-carbon sugar. A product of the hydrolysis of glucan found in cellulose and starch. A sweet, colorless sugar that is the most common sugar in nature and the sugar most commonly fermented to ethanol. (source: National Renewable Energy Laboratory)

Grain Sorghum: Grain sorghum (Sorghum bicolor (L.) Moench), also called milo, is currently produced in 18 states, although production is most concentrated in the central and southern Plains states of Nebraska, Kansas, Oklahoma, and Texas. Acreage has been declining, and average national yields are typically 50 to 70 bushel/ac with lower yields in the southern Plains relative to the central Plains (USDA NASS). Grain sorghum is an efficient water user and is drought tolerant, particularly with respect to other agricultural crops and is often produced in dryer areas.

Grain sorghum is produced primarily as cattle feed and is also used in bird seed. However, about 15% of the crop is currently used to produce ethanol or other bioproducts. The process used to produce ethanol from grain sorghum is the same as the dry grind process used for corn grain and similarly, results in the production of distiller’s dried grains that are used for livestock feed. (Source: National Sorghum Producers)

Greenhouse gases: Gaseous constituents of the atmosphere, which trap the heat of the sun in the earth’s atmosphere, producing what is commonly known as the greenhouse effect. Examples are water vapor, nitrous oxide, methane, carbon dioxide, hydrofluorocarbons (HFCs), perfluorocarbons (PFCs) and sulfur hexafluoride (SF6). (source: ASABE terms update)

Herbaceous energy crops: Perennial non-woody crops that are harvested annually, though they may take two to three years to reach full productivity. Examples include: Switchgrass (Panicum virgatum), Reed canarygrass (Phalaris arundinacea), Miscanthus (Miscanthus x giganteus), and Giant reed (Arundo donax). (source: National Renewable Energy Laboratory)

Higher Heating Value (or HHV): The full energy content of a fuel. It is the amount of heat produced when a liquied fuel or oven dried solid fuel is fully combusted, all of the products of combustion are cooled to 25o C (77o F) and the water vapor formed during combustion is condensed into liquid water. (source: ASABE terms update)

Hybrid: The offspring of genetically different parents. (source: National Renewable Energy Laboratory)

Hydrocarbon: An organic compound that contains only hydrogen and carbon. In vehicle emissions, these are usually vapors created from incomplete combustion or from vaporization of liquid gasoline. Emissions of hydrocarbons contribute to ground level ozone. (source: National Renewable Energy Laboratory)

Hydrolysis: The conversion, by reaction with water, of a complex substance into two or more smaller units, such as the conversion of cellulose into glucose sugar units. (source: National Renewable Energy Laboratory)

Incinerator: Any device used to burn solid or liquid residues or wastes as a method of disposal. In some incinerators, provisions are made for recovering the heat produced. (source: Biomass Energy Data Book)

Lignin: The major non-carbohydrate, polypenolic structural constituent of wood and other native plant material that encrusts the cell walls and cements the cells together. It is a highly polymeric substance, with a complex, cross-linked, highly aromatic structure of molecular weight about 10,000 derived principally from coniferyl alcohol (C10H12O3) by extensive condensation polymerization. Higher heating value (oven dry basis): HHV=9111 BTU/LB (5062 CAL/G, 21178 J/G). (Source: Domalski, E.S.; Milne T.A., ed. Thermodynamic Data for Biomass Materials and Waste Components. The ASME Research Committee on Industrial and Municipal Wastes, New York: The American Society of Mechanical Engineers, 1987) (source: National Renewable Energy Laboratory)

Lignocellulose: Biomass composed primarily of cellulose, hemicelluloses and lignin. (source: ASABE terms update)

Liquefaction: Thermochemical conversion process of carbon rich feedstocks into a liquid bio-oil and coproducts. Liquefaction is usually conducted in an environment of moderate temperatures (300 to 400o C or 572 to 752o F) and elevated pressures. (source: ASABE terms update)

Lower Heating Value (LHV) or Net Heating Value (NHV): Net heat released from the combustion of oven dry solid fuel after reducing the HHV by the heat of vaporization of the water generated by combustion of the hydrogen in the fuel. Each gram of hydrogen produces 9 grams of water. (source: ASABE terms update)

Methane: (CH4) The major component of natural gas. It can be formed by anaerobic digestion of biomass or gasification of coal or biomass. (source: National Renewable Energy Laboratory)

Methanol: Methanol, also known as methyl alcohol, is a light, volatile, colorless, flammable, poisonous liquid with the chemical formula CH3OH and a distinctive odor that is somewhat milder and sweeter than ethanol. Although most methanol today is produced synthetically, methanol is a natural product of anaerobic metabolism in many varieties of bacteria and can be produced on a large scale from biomass. Methanol is used as an antifreeze, a solvent, as a fuel, and as a denaturant for ethanol. (source: Sun Grant BioWeb)

Monoculture: The cultivation of a single species crop. (source: Sun Grant BioWeb)

Municipal Solid Waste (MSW): A waste stream consisting of post-consumer materials. (source: ASABE terms update)

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P - T

Particulates: A fine liquid or solid particle such as dust, smoke, mist, fumes, or smog, found in air or emissions. (source: National Renewable Energy Laboratory)

Pretreatment: Biological, chemical, physical, physico-chemical processing of biomass to reduce biomass recalcitrance to conversion. (source: ASABE terms update)

Primary biomass: Biomass produced by agriculture and forestry and includes energy crops and agricultural crops such as short rotation trees, grasses and aquatic plants. (source: Sun Grant BioWeb)

Producer gas: The mixture of gases produced by thermochemical gasification of organic material. Producer gas is composed of carbon monoxide (CO) and hydrogen (H2) plus carbon dioxide (CO2) and typically a range of hydrocarbons such as methane (CH4). (source: Sun Grant BioWeb)

Pyrolysis: The breaking apart of complex molecules by heating in the absence of oxygen, producing solid, liquid, and gaseous fuels. (source: National Renewable Energy Laboratory)

Renewable Energy: Energy derived from a natural, managed or cultivated resource that can be replaced as it is used. Examples are wind, solar, hydro, biomass or geothermal sources. (source: ASABE terms update)

Renewable Fuel Standards: On December 19, 2007, the Energy Independence and Security Act of 2007 (H.R. 6) was signed into law. This comprehensive energy legislation amends the Renewable Fuels Standard (RFS) signed into law in 2005, growing the RFS to 36 billion gallons in 2022. By doing so, the legislation seizes on the potential that renewable fuels offer to reduce foreign oil dependence and greenhouse gas emissions and provide meaningful economic opportunity across this country, putting America firmly on a path toward greater energy stability and sustainability. (source: Renewable Fuels Association)

Residues: Byproducts from processing all forms of biomass that have significant energy potential. For example, making solid wood products and pulp from logs produces bark, shavings and sawdust, and spent pulping liquors. Because these residues are already collected at the point of processing, they can be convenient and relatively inexpensive sources of biomass for energy. (source: Sun Grant BioWeb)

Sorghum: Sorghum, a grain, forage or sugar crop, is among the most efficient crops in conversion of solar energy and use of water. Sorghum is considered a high-energy, drought tolerant crop. (From Jack Harlan, 1971). (Source: National Sorghum Producers)

Stover: The dried stalks and leaves of a crop remaining after the grain has been harvested. (source: National Renewable Energy Laboratory)

Sugar platform: A conversion approach that involves the breakdown of biomass into component sugars, which are then converted into products such as ethanol and other valuable fuels and chemicals. (source: ASABE terms update)

Sustainable: An ecosystem condition in which biodiversity, renewability, and resource productivity are maintained over time. (source: Biomass Energy Data Book)

Switchgrass: Switchgrass (Panicum virgatum L.) is a warm season perennial bunch grass native to the tall grass prairies of North America. Its range now extends from Canada to Central America, where it is found in remnant prairies, along roadsides, pastures and as an ornamental plant in gardens. Long used as livestock forage, switchgrass is now being intensively studied as a dedicated energy crop because of its high potential fuel yields, drought tolerance, and ability to grow well on marginal land without heavy chemical use and intensive management. Potential uses of switchgrass are as a feedstock for cellulosic ethanol production, and as a supplement to coal for electricity generation. (source: Sun Grant BioWeb)

Syngas: A synthetic gas composed of hydrogen and carbon monoxide that is obtained by gasification of biomass when oxygen is fed to the reactor, and which can be transformed to fuels, products, power and hydrogen. (source: ASABE terms update)

Synthetic ethanol: Ethanol produced from ethylene, a petroleum by-product. (source: Biomass Energy Data Book)

Thermochemical conversion: The use of heat to change substances chemically to produce energy products. (source: National Renewable Energy Laboratory)

Thermochemical or Syngas Platform: A conversion approach that uses thermal processes, such as gasification and pyrolysis, to breakdown biomass into desired products or intermediate components which are in turn converted into desired fuels and chemicals. (source: ASABE terms update)

Torrefaction: A pretreatment method where biomass is subjected to moderate heating (200-300o C) in a low oxygen environment. (source: ASABE terms update)

Transesterification: A chemical reaction of exchanging the alkoxy group of an ester by another alcohol. The products of a transesterification reaction are a new ester and a new alcohol. A catalyst is typically required for transesterification. An example is when an alcohol reacts with the triglycerides contained in vegetable oils and animal fats to produce biodiesel, with glycerin as a byproduct. (source: ASABE terms update)

Wet torrefaction: A pretreatment process to convert biomass to energy-dense solid fuel with relatively uniform characteristics. Biomass is reacted with hot compressed water at temperature around 200-250o C. (source: ASABE terms update)


ASABE term update: ANSI/ASABE S593.1 JAN2011 Revision approved February 2011 as an American National Standard. Terminology and Definitions for Biomass Production, Harvesting and Collection, Storage, Processing, Conversion and Utilization.

Biomass Energy Centre

National Renewable Energy Laboratory

National Sorghum Producers

Renewable Fuels Association

Sun Grant BioWeb

U.S. Department of Energy EERE, Biomass Energy Data Book

U.S. Department of Energy, How Coal Gasification Power Plants Work

Wisconsin Biorefining Development Initiative
See for terms.

Content was compiled by Amanda Erichsen, Extension Assistant | Biosystems and Agricultural Engineering | Oklahoma State University | 218 B Agricultural Hall, Stillwater, OK 74078-6016