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agricultural residue: Plant parts, primarily stalks and leaves, not removed from fields with the primary food or fiber product. Examples include corn stover (stalks, leaves, husks and cobs), wheat straw and rice straw.
algae: Simple photosynthetic plants containing chlorophyll, often fast growing and able to live in freshwater, seawater or damp oils. May be unicellular and microscopic or very large, as in the giant kelps.
anaerobic: Living or active in an airless environment.
anaerobic digestion: Degradation of organic matter by microbes in the absence of oxygen to produce methane and CO2.
biodiesel: Biodegradable transportation fuel used in diesel engines. Biodiesel is produced through transesterification of organically derived oils and fats. It may be used either as a replacement for or component of diesel fuel.
bioenergy: Renewable energy produced from biomass.
biofuels: Fuels for transportation made from biomass or its derivatives after processing. The major biofuels include ethanol and biodiesel.
biogas: Gaseous mixture of CO2 and methane produced by anaerobic digestion of organic matter.
biomass: Any plant-derived organic matter. Biomass available for energy on a sustainable basis includes herbaceous and woody energy crops, agricultural food and feed crops, agricultural crop wastes and residues, wood wastes and residues, aquatic plants, and other waste materials, including some municipal wastes.
biopower: Use of biomass to produce electricity and heat.
bioproducts: Commercial or industrial products (other than food or feed) that are composed in whole or significant part of biomass.
carbohydrate: Organic compounds made up of carbon, hydrogen, and oxygen and having approximately the formula
(CH2O)n; includes cellulosics, starches, and sugars.
carbon dioxide: (CO2) Naturally occurring gas, and also a byproduct of burning fossil fuels and biomass, as well as land use changes and other industrial processes. It is the principal anthropogenic greenhouse gas that affects the earth’s radiative balance.
carbon monoxide: (CO) Colorless, odorless, poisonous gas produced by incomplete combustion.
catalyst: Substance that increases the rate of a chemical reaction without being consumed or produced by the reaction. Enzymes are catalysts for many biochemical reactions.
cellulase: Family of enzymes that break down cellulose into glucose molecules.
cellulose: Carbohydrate that is the principal constituent of wood and other biomass and forms the structural framework of the wood cells.
chips: Small fragments of wood chopped or broken by mechanical equipment. Total tree chips include wood, bark and foliage. Pulp chips or clean chips are free of bark and foliage.
cofiring: Use of a mixture of two fuels within the same combustion chamber.
cogeneration: Technology of producing electric energy and another form of useful energy (usually thermal) for industrial, commercial, or domestic heating or cooling purposes through sequential use of the energy source. Also called combined heat and power (CHP).
combustion: Chemical reaction between a fuel and oxygen that produces heat (and usually light).
coproducts: Resulting substances and materials that accompany production of a fuel product such as ethanol.
corn stover: Refuse of a corn crop after the grain is harvested.
criteria pollutants: Pollutants regulated under the federal NAAQS, which were established under the Clean Air Act. Criteria pollutants include CO, lead, nitrogen dioxide, PM (PM2.5, PM10), ground level ozone and SO2.
digester: Biochemical reactor in which anaerobic bacteria are used to decompose biomass or organic wastes into methane and CO2.
E10: Mixture of 10 percent ethanol and 90 percent gasoline based on volume.
E85: Mixture of 85 percent ethanol and 15 percent gasoline based on volume.
effluent: Liquid or gas discharged after processing activities, usually containing residues from such use. Also discharge from a chemical reactor.
energy crop: Crop grown specifically for its fuel value. These include food crops such as corn and sugar cane, and nonfood crops such as poplar trees and switchgrass.
enzyme: Protein or protein-based molecule that speeds up chemical reactions in living things. Enzymes act as catalysts for a single reaction, converting a specific set of reactants into specific products.
ester: Compound formed from the reaction between an acid and an alcohol.
ethanol: (CH3CH2OH) A colorless, flammable liquid produced by fermentation of sugars. Ethanol is used as a fuel oxygenate. Ethanol is the alcohol found in alcoholic beverages, but is denatured for fuel use.
eutrophic conditions: In surface waters, conditions such as significant algae growth and subsequent oxygen depletion, which can be caused by excessive nutrients from fertilizers, pesticides and herbicides. Some aquatic species cannot survive eutrophic conditions.
Source: Adapted from National Renewable Energy Laboratory (NREL) Glossary of Biomass Terms, www.nrel.gov/biomass/glossary.