Acetic acid

The acid most commonly associated with vinegar, it is the most commercially important organic acid and is used to manufacture a wide range of chemical products, such as plastics and acetobacter but, except for making vinegar, is usually made through synthetic processes. Derivatives of acetic acid which may be formed by substitution reactions. Mono- and di-substituted, as well as, halogenated compounds have been synthesised. Experimentally, alpha- and n2- substituted acetic acids have been examined for their anti-inflammatory activity and effect on the central nervous system respectively. Additionally, limited exposure data has been collected on dibromo and dichloroacetic acids to determine whether they pose health effects. (

Acid detergent fiber (ADF)

Organic matter that is not solubilized after one hour of refluxing in an acid detergent of cetyltrimethylammonium bromide in 1N sulfuric acid. ADF includes cellulose and lignin. This analytical method is commonly used in the feed and fiber industries. (Source: Milne, T.A.; Brennan, A.H.; Glenn, B.H. Sourcebook of Methods of Analysis for Biomass Conversion and Biomass Conversion Processes. SERI/SP-220-3548. Golden, CO: Solar Energy Research Institute, February 1990.)(NREL Biomass Glossary)

Acid hydrolysis

The treatment of cellulosic, starch, or hemicellulosic materials using acid solutions (usually mineral acids) to break down the polysaccharides to simple sugars.(NREL Biomass Glossary)

Acid insoluble lignin

Lignin is mostly insoluble in mineral acids, and therefore can be analyzed gravimetrically after hydrolyzing the cellulose and hemicellulose fractions of the biomass with sulfuric acid. ASTM E-1721-95 describes the standard method for determining acid insoluble lignin in biomass.(NREL Biomass Glossary)

Acid soluble lignin

A small fraction of the lignin in a biomass sample is solubilized during the hydrolysis process of the acid insoluble lignin method. This lignin fraction is referred to as acid soluble lignin and may be quantified by ultraviolet spectroscopy. (Source Ehrman, T. Determination of Acid-Soluble Lignin in Biomass. NREL-LAP-004. Golden, CO: National Renewable Energy Laboratory, September 9, 1996.)(NREL Biomass Glossary)


An emissions control device that removes VOCs from a gas stream as a result of the gas attaching (adsorbing) onto a solid matrix such as activated carbon. (CEPA)

Aerobic fermentation

Fermentation processes that require the presence of oxygen.(NREL Biomass Glossary)

Agricultural residue

Agricultural crop residues are the plant parts, primarily stalks and leaves, not removed from the fields with the primary food or fiber product. Examples include corn stover (stalks, leaves, husks, and cobs); wheat straw; and rice straw. (NREL Biomass Glossary)


An alcohol is an organic compound with a carbon bound to a hydroxyl group. Examples are methanol (CH3OH) and ethanol (CH3CH2OH).(NREL Biomass Glossary)


Any of a class of highly reactive organic chemical compounds characterized by the common group CHO and used in the manufacture of resins, dyes, and organic acids.(NREL Biomass Glossary)


A group of aquatic, photosynthetic, eukaryotic organisms ranging from unicellular to multicellular forms, and generally possess chlorophyll but lack true roots, stems and leaves characteristic of terrestrial plants.


A substance having highly basic properties; a strong base.

Alkali lignin

Lignin obtained by acidification of an alkaline extract of wood.(NREL Biomass Glossary)

Alkaline hydrolysis

The use of solutions of sodium hydroxide (or other alkali) in the treatment of cellulosic material (wood) to break down cellulose to simple sugars.(NREL Biomass Glossary)


Amylase is present in organisms such as molds, bacteria, yeasts and plants. In plants, the amylase can be found in seeds to break down starch into sugar to be used by the embryo to induce growth.


Occurring in the absence of oxygen or not requiring oxygen to live.

Anaerobic digestion

Degradation of organic matter by microbes in the absence of oxygen to produce methane and carbon dioxide.(NREL Biomass Glossary)

Anhydrous (adj.)

Containing no water.

Aquatic plants

Any plant adapted to grow in water or aqueous habitats


A polysaccharide that is mostly a polymer of arabinose.


A sugar of the pentose class that is a constituent of many plant gums.

Ash fusion temperature

The temperature at which a special test cone made from particles of ash obtained from the coal will (1) begin to deform, i.e., soften, or (2) completely deform or fuse into a blob. (


A tool resembling a large corkscrew, for boring holes in wood. (Oxford Dictionary)


100 percent biodiesel.


Fuel mix of 20% biodiesel and 80 diesel.


Sugar cane waste (

Batch distillation

A process in which the liquid feed is placed in a single container and the entire volume is heated, in contrast to continuous distillation in which the liquid is fed continuously through the still.

Batch fermentation

A process in which cells or micro-organisms are grown for a limited time. At the beginning of the fermentation, an inoculum is introduced into fresh medium, with no addition or removal of medium for the duration of the process.


Biobutanol is a 4-carbon alcohol (butyl alcohol) produced from the same feedstocks as ethanol including corn, sugar beets, and other biomass feedstocks. Butanol is generally used as an industrial solvent in products such as lacquers and enamels, but it also can be blended with other fuels for use in conventional gasoline vehicles (US Department of Energy).


A general term describing the use of biological systems to transform one compound into another. Examples are digestion of organic wastes or sewage by microorganisms to produce methane and the synthesis of organic compounds from carbon dioxide and water by plants. (US Biomass board)


An alternative fuel that can be made from any fat or vegetable oil; It can be used in any diesel engine with few or no modifications. Although biodiesel does not contain petroleum, it can be blended with diesel at any level or used in its pure form. (CWET)


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.(NREL Biomass Glossary)


Biomass converted to liquid or gaseous fuels such as ethanol, methanol, methane, and hydrogen.(NREL Biomass Glossary)


A gaseous mixture of carbon dioxide and methane produced by the anaerobic digestion of organic matter. (NREL Biomass Glossary)

Biogenic Source

Biological sources such as plants and animals that emit air pollutants such as volatile organic compounds. Examples of biogenic sources include animal management operations and oak and pine tree forests. (See also natural sources.) For more information, visit our Ecosystems Impact website. (CEPA)


"Bioliquids" means liquid fuel for energy purposes other than for transport, including electricity and heating and cooling, produced from biomass;(2009/28/EC)


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. Biomass is a very heterogeneous and chemically complex renewable resource.(NREL Biomass Glossary)

Biomass conversion

The process by which organic materials, such as wood waste or garbage, are burned for direct energy or electrical generation, or by which these materials are converted to synthetic natural gas (Platts)

Biomass processing 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. (NREL Biomass Glossary)


A landfill where the waste actively decomposes rather being simply buried in a "dry tomb (CWET)


Undergrowth, twigs, and small branches, typically used for firewood or kindling.


The layer of reproducing cells between the inner bark (phloem) and the wood (xylem) of a tree that repeatedly subdivides to form new wood and bark cells.(NREL Biomass Glossary)


Organic compounds made up of carbon, hydrogen, and oxygen. It includes cellulosics, starches, and sugars. (NREL Biomass Glossary)


The use of a mixture of two fuels within the same combustion chamber.(NREL Biomass Glossary)


Tree, usually evergreen, with cones and needle-shaped or scalelike leaves, producing wood known commercially as softwood. .(NREL Biomass Glossary)


The removal of a substantial portion of the water from any substance. (NREL Biomass Glossary)


The removal of hydrogen from a chemical compound.


A mixture of 10% ethanol and 90% gasoline based on volume.


The liquid or gas discharged after processing activities, usually containing residues from such use. Also discharge from a chemical reactor.

Elemental analysis

The determination of carbon, hydrogen, nitrogen, oxygen, sulfur, chlorine, and ash in a sample. See ultimate analysis. (NREL Biomass Glossary)

Energy crop

A 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. (NREL Biomass Glossary)


A compound formed from the reaction between an acid and an alcohol. In esters of carboxylic acids, the -COOH group of the acid and the -OH group of the alcohol lose water and become a -COO- linkage. (NREL Biomass Glossary)

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. (NREL Biomass Glossary)


Any material used as a fuel directly or converted to another form of fuel or energy product. (NREL Biomass Glossary)

Fischer-Tropsch process

A collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen into liquid hydrocarbons. The process, a key component of gas to liquids technology, produces a synthetic lubrication oil and synthetic fuel, typically from coal, natural gas, or biomass. (US Energy information administration)

Fixed bed

A bed of closely spaced particles through which gases move up or down for purposes of gasification or combustion. (NREL)

Fixed carbon

The carbon remaining after heating in a prescribed manner to decompose thermally unstable components and to distill volatiles. Part of the proximate analysis group. (NREL)

Flash point

The temperature at which a combustible liquid will ignite when a flame is held over the liquid; anhydrous ethanol will flash at 51 degrees Fahrenheit.

Flexible Fuel Vehicle

Automobile capable of running on gasoline and high-ethanol blends interchangeably (

Fluidized bed

A gasifier or combustor design in which feedstock particles are kept in suspension by a bed of solids kept in motion by a rising column of gas. The fluidized bed produces approximately isothermal conditions with high heat transfer between the particles and gases. (NREL)

Forestry residues

Includes tops, limbs, and other woody material not removed in forest harvesting operations in commercial hardwood and softwood stands, as well as woody material resulting from forest management operations such as pre-commercial thinnings and removal of dead and dying trees.(NREL Biomass Glossary)


Wood used for conversion to some form of energy, primarily in residential use. (NREL)


Plant-like organisms with cells with distinct nuclei surrounded by nuclear membranes, incapable of photosynthesis. Fungi are decomposers of waste organisms and exist as yeast, mold, or mildew. (NREL)


An aldehyde derivative of certain biomass conversion processes; used as a solvent. (NREL)


Any chemical or heat process used to convert a feedstock to a gaseous fuel.


A gasoline extender made from a mixture of gasoline (90%) and ethanol ethanol or wood alcohol (3%).

Glowing combustion

A reaction between oxygen or an oxidizer and the surface of a solid fuel, allowing emission of heat and light without a flame - also known as surface burning.

Guarantee of Origin

An electronic certificate representing 1 MWh of electricity production used for the purpose of proving to final customers the share or quantity of renewable energy that was supplied to them. (Directive 2009/28/ec)


One of the botanical groups of dicotyledonous trees that have broad leaves in contrast to the conifers or softwoods. The term has no reference to the actual hardness of the wood. The botanical name for hardwoods is angiosperms. Short-rotation, fast growing hardwood trees are being developed as future energy crops.

Heat rate

The amount of fuel energy required by a power plant to produce one kilowatt-hour of electrical output. A measure of generating station thermal efficiency, generally expressed in Btu per net kWh. It is computed by dividing the total Btu content of fuel burned for electric generation by the resulting net kWh generation.

Heat transfer efficiency

Useful heat output released / actual heat produced in the firebox.

Heating value

Higher heating value (HHV) is the potential combustion energy when water vapor from combustion is condensed to recover the latent heat of vaporization. Lower heating value (LHV) is the potential combustion energy when water vapor from combustion is not condensed.


Any of various simple sugars that have six carbon atoms per molecule

Higher heating value (HHV)

The heat produced by combustion of one unit of substance at constant volume in an oxygen bomb calorimeter under specified conditions. The conditions are: initial oxygen pressure of 2.0-4.0 MPa (20-40 atm), final temperature of 20°-35°C, products in the form of ash, liquid water, gaseous CO2 and N2, and dilute aqueous HCl and H2SO4. It is assumed that if significant quantities of metallic elements are combusted, they are converted to their oxides. In the case of materials such as coal, wood, or refuse, if small or trace amounts of metallic elements are present, they are unchanged during combustion and are part of the ash. Also known as gross heat of combustion.


The total carbohydrate fraction of wood; cellulose plus hemicellulose.


The offspring of genetically different parents The term is applied as well to the progeny from matings within species and to those between species. Hybrids combine the characteristics of the parents or exhibit new ones.


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.


A process in which hydrogen is added to organic molecules at high pressures and moderate temperatures; usually used as an adjunct to catalytic cracking.


Treatment of substances with hydrogen and suitable catalysts at high temperature and pressure to saturate double bonds.


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.

Incremental energy costs

The cost of producing and/or transporting the next available unit of electrical energy above a previously determined base cost. NREL


Tropical plant emerging as a potential new feedstock for biodiesel due to its resistance to drought and pests, and its seeds which contain up to 40% oil. When crushed and processed, the seeds’ oil can be used in a standard diesel engine and its residue can be processed into biomass. (Chartis)

Klason lignin

Lignin obtained from wood after the non-lignin components of the wood have been removed with a prescribed sulfuric acid treatment. A specific type of acid-insoluble lignin analysis. NREL


Engine sound that results from ignition of the compressed fuel-air mixture prior to the optimal moment. EFC

Kraft process

Chemical pulping process in which lignin is dissolved by a solution of sodium hydroxide and sodium sulfide. NREL

Landfill gas

Biogas produced from the natural degradation of organic material in landfills. NREL


Energy-rich material contained in biomass that can be used for boiler fuel. EFC

Lignin pseudo-molecule for modeling

The lignin ratio of methoxy groups to phenylpropanoid groups (MeO:C9) is used to calculate an ultimate analysis for the lignin pseudo-molecule. This ultimate analysis is used to estimate other properties of the molecule, such as its higher and lower heating values. NREL


Refers to plant materials made up primarily of lignin, cellulose, and hemicellulose. logging residues: The unused portions of growing-stock and non-growing-stock trees cut or killed by logging and left in the woods. US biomass board

Lower heating value (LLV)

The heat produced by combusting one unit of a substance, at atmospheric pressure under conditions such that all water in the products remains in the form of vapor. The net heat of combustion is calculated from the gross heat of combustion at 20°C by subtracting 572 cal/g (1030 Btu/lb) of water derived from one unit mass of sample, including both the water originally present as moisture and that formed by combustion. This subtracted amount is not equal to the latent heat of vaporization of water because the calculation also reduces the data from the gross value at constant volume to the net value at constant pressure. The appropriate factor for this reduction is 572 cal/g.


The polymer of mannose with a repeating unit of C6H10O5. Can be hydrolyzed to mannose.


(C6H1206) A six-carbon sugar. A product of hydrolysis of mannan found in the hemicellulose fraction of biomass.


Mixture of grain and water that is converted through the fermentation process into alcohol.

Mass closure (%)

The percent by weight of the total samples extracted from the biomass sample compared to the weight of the original sample. It is a sum of the weight percent of moisture, extractives, ash, protein, total lignin, acetic acid, uronic acids, arabinan, xylan, mannan, galactan, glucan, and starch. This is a good indicator of the accuracy of a complete biomass compositional analysis.


The sum of the physical and chemical processes involved in the maintenance of life and by which energy is made available to the organism.


(CH4) The major component of natural gas. It can be formed by anaerobic digestion of biomass or gasification of coal or biomass.

Methanol (wood alcohol)

(CH3OH) An alcohol formed by catalytically combining carbon monoxide with hydrogen in a 1:2 ratio under high temperature and pressure.


Any microscopic organism such as yeast, bacteria, fungi, etc.

Mill Residue

Wood and bark residues produced in processing logs into lumber, plywood, and paper.


A common method of pricing electricity in the U.S. Tenths of a U.S. cent per kilowatt hour.


The amount of water and other components present in the biomass sample that are volatilized at 105oC.

Moisture free basis

Biomass composition and chemical analysis data is typically reported on a moisture free or dry weight basis. Moisture (and some volatile matter) is removed prior to analytical testing by heating the sample at 105oC to constant weight. By definition, samples dried in this manner are considered moisture free.


The cultivation of a single species crop.


A simple sugar such as a five-carbon sugar (xylose, arabinose) or six-carbon sugar (glucose, fructose). Sucrose, on the other hand is a disaccharide, composed of a combination of two simple sugar units, glucose and fructose.

Municipal solid waste

Any organic matter, including sewage, industrial, and commercial wastes, from municipal waste collection systems. Municipal waste does not include agricultural and wood wastes or residues.

Native lignin

The lignin as it exists in the lignocellulosic complex before separation.

Net heat of combustion

see lower heating value

Neutral detergent fiber (NDF)

Organic matter that is not solubilized after one hour of refluxing in a neutral detergent consisting of sodium lauryl sulfate and EDTA at pH 7. NDF includes hemicellulose, cellulose, and lignin.

Nitrogen fixation

The transformation of atmospheric nitrogen into nitrogen compounds that can be used by growing plants.

Nitrogen oxides (NOx)

A product of photochemical reactions of nitric oxide in ambient air, and the major component of photochemical smog.

Non-condensing, controlled extraction turbine

A turbine that bleeds part of the main steam flow at one (single extraction) or two (double extraction) points.

Non-forest land

Land that has never supported forests and lands formerly forested where use of timber management is precluded by development for other uses.


Measure of a fuel’s resistance to self-ignition (see ‘Knock’)

Organic compound

An organic compound contains carbon chemically bound to hydrogen. Organic compounds often contain other elements (particularly O, N, halogens, or S).

Oven dry ton

An amount of wood that weighs 2000 lb at 0% moisture content.


An oxygenate is a compound which contains oxygen in its molecular structure. Ethanol and biodiesel act as oxygenates when they are blended with conventional fuels. Oxygenated fuel improves combustion efficiency and reduces tailpipe emissions of CO.


A fine liquid or solid particle such as dust, smoke, mist, fumes, or smog, found in air or emissions.


A short cylindrical piece meant for burning, produced through compressing pulverized dry biomass, such as corn stalk, cassava stalk, waste wood, sawdust, pinchip, etc


Plant that doesn’t have to be planted every year like traditional row crops. EFC


Any petroleum-based substance composed of a complex blend of hydrocarbons derived from crude oil, including motor fuel, jet oil, lubricants, petroleum solvents, and used oil.


In plants, the inner bark; the principal tissue in a tree concerned with the transport of sugars and other nutrients from the leaves.


Conversion of light into other forms of energy by chemical, biological, or physical processes.


A large molecule made by linking smaller molecules (monomers) together.


A long-chain carbohydrate containing at least three molecules of simple anhydrous sugars linked together. Examples include cellulose and starch.

Process development unit

An experimental facility that establishes proof of concept, preliminary process economics, and engineering feasibility for a pilot or demonstration plant.

Process heat

Energy, usually in the form of hot air or steam, needed in the manufacturing operations of an industrial plant.


The ethanol content of a liquid at 60 degrees Fahrenheit stated as twice the percent by volume of the ethyl alcohol.


A protein molecule is a chain of up to several hundred amino acids and is folded into a more or less compact structure. Because about 20 different amino acids are used by living matter in making proteins, the variety of protein types is enormous. In their biologically active states, proteins function as catalysts in metabolism and to some extent as structural elements of cells and tissues.

Proximate analysis

The determination, by prescribed methods, of moisture, volatile matter, fixed carbon (by difference), and ash. The term proximate analysis does not include determinations of chemical elements or determinations other than those named.


The breaking apart of complex molecules by heating in the absence of oxygen, producing solid, liquid, and gaseous fuels.


A chemical reaction is a dissociation, recombination, or rearrangement of atoms.

Recombinant DNA

DNA that has been artificially introduced into a cell, resulting in alteration of the genotype and phenotype of the cell, and is replicated along with natural DNA. Used in industrial micro-organisms to produce more productive strains.

Renewable diesel

Biofuel technology whereby fuel is created from biomass, oils, and fats without a chemical process. Advantages of renewable diesel include improved ignition, higher renewable content, greater fuel stability, a broader selection of feedstock, and lower greenhouse gas emissions. Chartis

Residues in biomass

Byproducts from processing all forms of biomass that have significant energy potential such as, 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.


A simple sugar or a more complex compound that can be hydrolyzed to simple sugar units.


A conversion process using acids, bases, or enzymes in which long-chain carbohydrates are broken down into their component fermentable sugars.


An air pollution control device that uses a liquid or solid to remove pollutants from a gas stream by adsorption or chemical reaction.

Short Rotation Intensive Culture (SRIC)

The growing of tree crops for bioenergy or fiber, characterized by detailed site preparation, usually less than 10 years between harvests, usually fast-growing hybrid trees and intensive management (some fertilization, weed and pest control, and possibly irrigation).

Slow pyrolysis

Thermal conversion of biomass to fuel by slow heating to less that 842 degrees Fahrenheit (450 degrees Celsius) in the absence of oxygen.


Generally, one of the botanical groups of trees that in most cases have needle-like or scale-like leaves; the conifers; also the wood produced by such trees. The term has no reference to the actual hardness of the wood. The botanical name for softwoods is gymnosperms.


A molecule composed of long chains of a-glucose molecules linked together (repeating unit C12H16O5). These linkages occur in chains of a-1,4 linkages with branches formed as a result of a-1,6 linkages (see below). This polysaccharide is widely distributed in the vegetable kingdom and is stored in all grains and tubers.


The dried stalks and leaves of a crop remaining after the grain has been harvested.

Structural chemical analysis

The composition of biomass reported by the proportions of the major structural components; cellulose, hemicellulose, and lignin.


The base on which an organism lives or a substance acts upon (as by an enzyme).


A component of lignin, normally only found in hardwood lignins. It has a six-carbon aromatic ring with two methoxyl groups attached.


A liquid product of thermal processing of carbonaceous materials.

Thermochemical conversion

The use of heat to change substances chemically to produce energy products.

Total lignin

The sum of the acid soluble lignin and acid insoluble lignin fractions.

Total solids

The amount of solids remaining after all volatile matter has been removed from a biomass sample by heating at 105°C to constant weight.


A chemical process which reacts an alcohol with the triglycerides contained in vegetable oils and animal fats to produce biodiesel and glycerin.


A triglyceride is an ester of glycerol and three fatty acids. Most animal fats are composed primarily of triglycerides.

Ultimate analysis

The determination of the elemental composition of the organic portion of carbonaceous materials, as well as the total ash and moisture. See elemental analysis

Uronic acid

A simple sugar whose terminal -CH2OH group has been oxidized to an acid, COOH group.

Vacuum distillation

The separation of two or more liquids under reduced vapor pressure; reduces the boiling points of the liquids being separated.


A solid or liquid material that easily vaporizes.

Volatile matter

Those products, exclusive of moisture, given off by a material as a gas or vapor, determined by definite prescribed methods that may vary according to the nature of the material.

Wet scrubber

An air pollution control device used to remove pollutants by bringing a gas stream into contact with a liquid.

Whole tree chips

Wood chips produced by chipping whole trees, usually in the forest. Thus the chips contain both bark and wood. They are frequently produced from the low-quality trees or from tops, limbs, and other logging residues.

Willstatter lignin

Lignin obtained from the lignocellulosic complex after it has been extracted with hydrochloric acid.


A solid lignocellulosic material naturally produced in trees and some shrubs, made of up to 40%-50% cellulose, 20%-30% hemicellulose, and 20% -30% lignin.


The liquid remaining from a brewing mash preparation following the filtration of fermentable beer.


A polymer of xylose with a repeating unit of C5H804, found in the hemicellulose fraction of biomass. Can be hydrolyzed to xylose. Gross heat of combustion: Qv(gross)=17751.9 Jg-1.


(C5H10O5) A five-carbon sugar. A product of hydrolysis of xylan found in the hemicellulose fraction of biomass.


The initial movement of logs from the point of felling to a central loading area or landing.


Any of various single-cell fungi capable of fermenting carbohydrates.