Gas flaring and venting - Method by which excess natural gas typically found at oil wells and refineries is burned in order to prevent the buildup of excess pressure. Flaring and venting are major contributors to greenhouse gas emission.

Gas reburning - Process designed to reduce the emission of nitrous oxides generated by natural gas boilers by injecting natural gas above the boilers’ coal burners in order to “reburn” the byproducts of combustion.

Gasification - Method that extracts energy from organic materials. Carbon-based matter (e.g. coal) reacts at high temperatures with oxygen producing synthesis gas. Process can be more efficient than direct combustion of carbon material and is considered to be more environmentally sound as well.

Gasoline grades - Classification system that categorizes gasoline by octane ratings. The three types of gasoline (conventional, oxygenated, and reformulated) are further broken down into regular, midgrade and premium categories, all based on octane content.

Generators - Machines that convert one type of energy, such as kinetic or mechanical, into electrical energy.

Global warming potential (GWP) - Measure of a given pollutant’s estimated contribution to global warming. Scale is relative and compares the gas in question to that of the same mass of carbon dioxide.

Green devices - Electronic devices used inside buildings (including lighting solutions, appliances and consumer electronics) that are more energy efficient than conventional alternatives.

Greenfield refineries - Refinery facilities that are built on sites that have not experienced previous development.

Greenhouse gas (GHG) - Gas in the atmosphere that absorbs and emits radiation within the thermal infrared range (including water vapor, carbon dioxide, methane, nitrous oxide, ozone and chlorofluorocarbons).

Greywater systems - Systems that focus on the reuse of water generated from domestic processes such as dish washing, laundry and bathing for either indoor use or in irrigation.