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SAN LEANDRO SHORELINE DEVELOPMENT DRAFT EIR <br />CITY OF SAN LEANDRO <br />GREENHOUSE GAS EMISSIONS <br />Fluorinated gases are synthetic, strong GHGs that are emitted from a variety of industrial processes. <br />Fluorinated gases are sometimes used as substitutes for ozone-depleting substances. These gases are <br />typically emitted in smaller quantities, but because they are potent GHGs, they are sometimes <br />referred to as high global -warming -potential (GWP) gases. <br />■ Chlorofluorocarbons (CFCs) are GHGs covered under the 1987 Montreal Protocol and used for <br />refrigeration, air conditioning, packaging, insulation, solvents, or aerosol propellants. Since they <br />are not destroyed in the lower atmosphere (troposphere), CFCs drift into the upper atmosphere <br />where, given suitable conditions, they break down the ozone layer. These gases are therefore <br />being replaced by other compounds that are GHGs covered under the Kyoto Protocol. <br />■ Perfluorocarbons (PFCs) are a group of human -made chemicals composed of carbon and fluorine <br />only. These chemicals (predominantly perfluoromethane [CF4] and perfluoroethane 1C2F6]) were <br />introduced as alternatives, along with HFCs, to ozone-depleting substances. In addition, PFCs are <br />emitted as by-products of industrial processes and are used in manufacturing. PFCs do not harm <br />the stratospheric ozone layer, but they have a high GWP. <br />■ Sulfur Hexafluoride (SF6) is a colorless gas soluble in alcohol and ether, and slightly soluble in <br />water. SF6 is a strong GHG used primarily in electrical transmission and distribution systems as an <br />insulator. <br />■ Hydrochlorofluorocarbons (HCFCs) contain hydrogen, fluorine, chlorine, and carbon atoms. <br />Although they are ozone-depleting substances, they are less potent than CFCs. They have been <br />introduced as temporary replacements for CFCs. <br />■ Hydrofluorocarbons (HFCs) contain only hydrogen, fluorine, and carbon atoms. They were <br />introduced as alternatives to ozone-depleting substances to serve many industrial, commercial, <br />and personal needs. HFCs are emitted as by-products of industrial processes and are also used in <br />manufacturing. They do not significantly deplete the stratospheric ozone layer, but they are <br />strong GHG S.4,1 <br />GHGs are dependent on the lifetime or persistence of the gas molecule in the atmosphere. Some GHGs <br />have stronger greenhouse effects than others. These are referred to as high GWP gases. The GWP of GHG <br />emissions are shown in Table 4.6-1. The GWP is used to convert GHGs to CO2 -equivalence (CO2e) to show <br />the relative potential that different GHGs have to retain infrared radiation in the atmosphere and <br />contribute to the greenhouse effect. For example, under IPCC's Second Assessment Report GWP values <br />for CH4i a project that generates 10 metric tons (MT) of CH4 would be equivalent to 210 MT of CO2.6 <br />4 United States Environmental Protection Agency, 2012. Greenhouse Gas Emissions, http://www.epa.gov/climatechange/ <br />ghgemissions/gases.html. <br />5 Intergovernmental Panel on Climate Change, 2001. Third Assessment Report: Climate Change 2001, New York: <br />Cambridge University Press. <br />6 CO2 -equivalence is used to show the relative potential that different GHGs have to retain infrared radiation in the <br />atmosphere and contribute to the greenhouse effect. The global warming potential of a GHG is also dependent on the lifetime, <br />or persistence, of the gas molecule in the atmosphere. <br />4.6-2 DECEMBER 2014 <br />