Galactan: The polymer of galactose with a repeating unit of C6H10O5. Found in hemicellulose it can be hydrolyzed to galactose.

Galactose: A six-carbon sugar with the formula C6H1206. A product of hydrolysis of galactan found in the hemicellulose fraction of biomass.

Gas to liquid (GTL): a refinery process which converts natural gas into longer-chain hydrocarbons. Gas can be converted to liquid fuels via a direct conversion or using a process such as Fischer-Tropsch.

Gas Shift Process: A process in which carbon monoxide and hydrogen react in the presence of a catalyst to form methane and water.

Gas turbine: Sometimes called a combustion turbine; a gas turbine converts the energy of hot compressed gases (produced by burning fuel in compressed air) into mechanical power, which can be used to generate electricity.

Gaseous Emissions: Substances discharged into the air during combustion, typically including carbon dioxide, carbon monoxide, water vapor, and hydrocarbons.

Gasification: is the conversion of biomass into a combustible gas mixture by the partial oxidation of biomass at high temperatures, typically in the range 800–900 oC. The low calorific value (CV) gas produced can be burnt directly or used as a fuel for gas engines and gas turbines. The product gas can be used as a feedstock (syngas) in the production of chemicals (e.g. methanol).

Gasifier: A device that converts solid fuel to gas. Generally refers to thermochemical processes.

Gasohol: A mixture of 10 percent anhydrous ethanol and 90 percent gasoline by volume; 7.5 percent anhydrous ethanol and 92.5 percent gasoline by volume; or 5.5 percent anhydrous ethanol and 94.5 percent gasoline by volume.

Gel point: The point at which a liquid fuel cools to the consistency of petroleum jelly.

Genetically modified organism (GMO): An organism whose genetic material has been modified through recombinant DNA technology, altering the phenotype of the organism to meet desired specifications.

Genetic Selection: Application of science to systematic improvement of a population, e.g. through selective breeding.

Generator: A machine used for converting rotating mechanical energy to electrical energy.

Geographic Information System (GIS): GIS technology is increasingly used as a framework for gathering and organizing spatial data and related information so it can be displayed and analyzed. A GIS is an integrated collection of computer software and data used to view and manage information about geographic places, analyze spatial relationships, and model spatial processes. A GIS enables users to quickly visualize data, extract trends, optimize routes, and interpret other relationships via maps and charts. The technology helps solve problems and answer questions by presenting complex data in understandable and easily sharable ways.

Giant Miscanthus: Giant Miscanthus (an "energy cane") is a perennial warm season grass in the sugarcane complex that has considerable potential as a biomass crop in North Carolina to supply feedstock for cellulosic ethanol production and for gasification to gasoline processing. Giant Miscanthus is characterized as having broad adaptability, high water and fertilizer use efficiency, excellent pest resistance, and tremendous biomass production.

Gigawatt (GW): A measure of electrical power equal to one billion watts (1,000,000 kW). A large coal or nuclear power station typically has a capacity of about 1 GW.

Global Climate Change: Global climate change could result in sea level rises, changes to patterns of precipitation, increased variability in the weather, and a variety of other consequences. These changes threaten our health, agriculture, water resources, forests, wildlife, and coastal areas.

Glucan: The polymer of glucose with a repeating unit of C6H10O5. Cellulose is a form of glucan. Can be hydrolyzed to glucose.

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.

Glycerin: (C3H8O3) A liquid by-product of biodiesel production. Glycerin is used in the manufacture of dynamite, cosmetics, liquid soaps, inks, and lubricants.

Grade: Utilization and established quality or use classification of lumber, trees, or other forest products.

Grassland pasture and range: All open land used primarily for pasture and grazing, including shrub and brush land types of pasture; grazing land with sagebrush and scattered mesquite; and all tame and native grasses, legumes, and other forage used for pasture or grazing; because of the diversity in vegetative composition, grassland pasture and range are not always clearly distinguishable from other types of pasture and range; at one extreme, permanent grassland may merge with cropland pasture, or grassland may often be found in transitional areas with forested grazing land.

Grates (or combustion grates): Slotted or pinhole grates that support the burning fuel and allow air to pass up through the fuel bed from below.

Grease car: A diesel-powered automobile rigged postproduction to run on used vegetable oil.

Green Biomass Fuel : Biomass fuel that has not been significantly dried, with approximately the same moisture content as at harvest.

Green Chemistry : Also known as sustainable chemistry, is a chemical philosophy encouraging the design of products and processes that reduce or eliminate the use and generation of hazardous substances.

Green diesel: A diesel fuel substitute made from renewable feedstocks by using traditional distillation methods. It is also known as renewable diesel.

Green gasoline: A liquid identical to petroleum-based gasoline, but is produced from biomass such as switchgrass and poplar trees. In the United States, it is still in the development stages. It is also known as renewable gasoline.

Greenhouse effect: The effect of certain gases in the earth’s atmosphere in trapping heat from the sun.

Greenhouse gas: A gas, such as water vapor, carbon dioxide, tropospheric ozone, methane, and low level ozone, which contributes to the greenhouse effect.

Green Power Purchasing/Aggregation Policies: Municipalities, state governments, businesses, and other non-residential customers can play a critical role in supporting renewable energy technologies by buying electricity from renewable resources. At the local level, green power purchasing can mean buying green power for municipal facilities, streetlights, water pumping stations and other public infrastructure. Several states require that a certain percentage of electricity purchased for state government buildings come from renewable resources. A few states allow local governments to aggregate the electricity loads of the entire community to purchase green power and even to join with other communities to form an even larger green power purchasing block. This is often referred to as "Community Choice." Green power purchasing can be achieved via utility green pricing programs, green power marketers (in states with retail competition), special contracts, or community aggregation.

Green ton: 2000 pounds worth of biomass typically at 50% moisture.

Grid: An electric utility company’s system for distribution power.

Grinder: A machine that reduce particles in size by repeatedly pounding them into smaller pieces through a combination of tensile, shear and compressive forces.

Gross heat of combustion: see higher heating value.

Group Selection: Is an uneven-aged regeneration method used for sun loving tree species in which trees are removed and new age classes are established in groups. The width of a group is approximately twice the height of mature trees.

Growing Stock: A classification of timber inventory that includes live trees of commercial species meeting specified standards of quality or vigor; cull trees are excluded.

Guaiacyl: A chemical component of lignin. It has a six-carbon aromatic ring with one methoxyl group attached. It is the predominant aromatic structure in softwood lignins

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