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

E-85: A mixture of 85% ethanol and 15% gasoline based on volume.

Ecology: The science or study of the relationships between organisms and their environment.

Effluent: The liquid or gas discharged from a process or chemical reactor, usually containing residues from that process.

Elemental analysis: The determination of carbon, hydrogen, nitrogen, oxygen, sulfur, chlorine, and ash in a sample. See ultimate analysis.

Emission: Substance discharged into the air during combustion, for example, all that stuff that comes out of your car.

Embedded energy: The total amount of energy used in the production of a fuel or product . For woodfuel this may include contributions from land preparation, planting, fertilizer and pesticide inputs, thinning, harvesting, comminution, processing, and transport.

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.

Energy balance: The difference between the energy produced by a fuel and the energy required to obtain it through agricultural processes, drilling, refining, and transportation.

Energy density: The amount of energy stored per unit volume (volume energy density) or mass (mass energy density) of a fuel. A high energy density generally make storage and transport of a fuel more convenient. Fossil fuels typically have higher energy density than solid or wet biomass fuels, though converted liquid biofuels and biogas are similar to those of their fossil counterparts.

Energy-efficiency ratio: A number representing the energy stored in a fuel as compared to the energy required to produce, process, transport, and distribute that fuel.

Enhanced recovery: Methods that usually involve the application of thermal energy (e.g., steam flooding) to oil recovery from the reservoir.

Environment: The interaction of climate, soil, topography, and other plants and animals in any given area. An organism’s environment influences its form, behavior, and survival.

Enzymatic hydrolysis:  Use of an enzyme to promote the conversion, by reaction with water, of a complex substance into two or more smaller molecules.

Enzyme: An enzyme is a protein or protein-based molecule that speeds up chemical reactions occurring in living things. Enzymes act as catalysts for a single reaction, converting a specific set of reactants into specific products.

ESCO: Energy supply company. Sells heat to the customer instead of a boiler and/or fuel. May install, own and maintain the boiler, or may sub-contract some or all of that. Heat used by the customer is metered, usually as hot water flow rate and temperature difference between outflow and return. Fully responsible for ensuring continuous operation and suitable quality fuel supply. Particularly well suited to district, site or large or multiple building heating systems.

Ester: An ester is 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.

Ethanol: (CH3CH2OH) A colorless, flammable liquid produced by fermentation of sugars. Ethanol is used as a fuel oxygenate.

Evaporation: is a type of vaporization of a liquid that only occurs on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs within the entire mass of the liquid.

Even-aged Management: Management technique for a stand of trees composed of a single age class.

Excess air: The amount of combustion air supplied to the fire that exceeds the theoretical air requirement to give complete combustion. Expressed as a percentage.

Exotic species: Introduced species not native or endemic to the area in question.

Externality: A cost or benefit not accounted for in the price of goods or services. Often "externality" refers to the cost of pollution and other environmental impacts.

Extractives: Any number of different compounds in biomass that are not an integral part of the cellular structure. The compounds can be extracted from wood by means of polar and non-polar solvents including hot or cold water, ether, benzene, methanol, or other solvents that do not degrade the biomass structure. The types of extractives found in biomass samples are entirely dependent upon the sample itself.

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