ACFM: Actual cubic feet per minute. The actual cubic feet per minute of gas flowing in a process at the temperature and pressure of the process at that point.

Acid hydrolysis: A chemical process in which acid is used to convert cellulose or starch to sugar.

Aerobic: Life or biological processes that can occur only in the presence of oxygen.

Alcohol: A general class of hydrocarbons that contain a hydroxyl group (OH). The term "alcohol" is often used interchangeably with the term "ethanol," even though there are many types of alcohol. (See Butanol, Ethanol, Methanol.)

Alkali: A soluble mineral salt.

Alternative: Under the National Environmental Policy Act, a comprehensive management strategy. When a federal agency is considering an action, the agency must develop and analyze a range of alternatives. The alternatives must show a reasonable range of actions, including a "no action" alternative.

Alternative fuel: As defined in the Energy Policy Act of 1992 (EPACT):

• Methanol, denatured ethanol and other alcohols, separately or in blends of at least 10 percent by volume with gasoline or other fuels
• Compressed natural gas (CNG)
• Liquefied natural gas (LNG)
• Liquefied propane gas (LPG)
• Hydrogen
• Coal derived liquid fuels
• Fuels other than alcohols derived from biological materials
• Electricity
• Biodiesel

Any other fuel determed to be substantially not petroleum and yielding potential energy security benefits and substantial environmental benefits.

Ambient air quality: The condition of the air in the surrounding environment.

Barrel of oil equivalent: A unit of energy equal to the amount of energy contained in a barrel of crude oil. Approximately 5.78 million Btu or 1,700 kWh. A barrel is a liquid measure equal to 42 gallons.

Benzene: A toxic, six-carbon aromatic component of gasoline. A known carcinogen.

Biodegradable: Capable of decomposing rapidly under natural conditions.

Biodiesel: A biofuel produced through transesterification, a process in which organically-derived oils are combined with alcohol (ethanol or methanol) in the presence of a catalyst to form ethyl or methyl ester. The biomass-derived ethyl or methyl esters can be blended with conventional diesel fuel or used as a neat fuel (100% biodiesel). Biodiesel can be made from soybean or rapeseed oils, animal fats, waste vegetable oils or microalgae oils.

Bioenergy: Renewable energy produced from organic matter. The conversion of the complex carbohydrates in organic matter to energy. Organic matter may either be used directly as a fuel or processed into liquids or gases.

Biofuels: Fuels made from biomass. Biofuels include ethanol, biodiesel and methanol.

Biogas: A combustible gas derived from decomposing biological waste. Biogas normally consists of 50 to 60 percent methane.

Biomass: Renewable organic matter such as agricultural crops and residue, wood and wood waste, animal waste, aquatic plants and organic components of municipal and industrial wastes.

Biomass fuel: Liquid, solid or gaseous fuel produced by conversion of biomass.

Bone dry: Having zero percent moisture content. Wood heated in an oven at a constant temperature of 212 degrees F or above until its weight stabilizes is considered bone dry or oven dry.

Bone dry ton: (or " oven dry ton"). An amount of wood that weighs 2,000 pounds at zero percent moisture content.

Bone dry unit: (BDU) A quantity of woo