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Draft Supplemental Environmental Impact Report Page IV.D-6 Forward Inc. Landfill 2014 Expansion Project ion Greenhouse Gases Some gases in the atmosphere affect the Earth's heat balance by absorbing infrared radiation.These gases can prevent the escape of heat in much the same way as glass in a greenhouse.This is often referred to as the "greenhouse effect," and it is responsible for maintaining a habitable climate. The gases believed to be most responsible for global warming are carbon dioxide (CO2), methane (CH4), nitrous oxide(N2O), .. hydrofluorocarbons (HFCs), perfluorocarbons(PFCs), and sulfur hexafluoride (SF6). Enhancement of the greenhouse effect can occur when concentrations of these gases exceed the natural concentrations in the atmosphere. Of these gases, CO2 and CH4 are emitted in the greatest quantities from human activities. Emissions of CO2 are largely by-products of fossil fuel combustion, whereas CH, primarily results from off-gassing associated with agricultural practices and landfills. SF6 is a GHG commonly used in the utility industry as an insulating gas in transformers and other electronic equipment.SF6,while comprising a small fraction of the total GHGs emitted annually world-wide,is a very potent GHG with 23,900 times the global ;.. warming potential as CO2 over a 100 year period. To account for the warming potential of GHGs, GHG emissions are often quantified and reported as CO2 equivalents(CO2e). The effects of GHG emission sources (i.e., individual projects) are reported in metric i tons/year of CO2e.There is widespread international scientific agreement that human- caused increases in GHGs has and will continue to contribute to global warming, although there is much uncertainty concerning the magnitude and rate of the warming. Some of the potential resulting effects in California of global warming may include loss in snow pack, sea level rise, more extreme heat days per year, more high ozone days, more large forest fires, and more drought years. Globally, climate change has the potential to affect numerous environmental resources through potential, though uncertain,impacts related to future air temperatures and precipitation patterns.The projected effects of global warming on weather and climate are likely to vary regionally,but are expected to r. include the following direct effects(IPCC, 2007): • Higher maximum temperatures and more hot days over nearly all land areas; • Higher minimum temperatures, fewer cold days, and fewer frost days over nearly all land areas; • Reduced diurnal temperature range over most land areas; • Increase of heat index over land areas; and • More intense precipitation events. Landfills typically emit some CO2 and methane from the creation of landfill gas. When municipal solid wastes are buried in a landfill, a complex series of biochemical reactions raw occur in which anaerobic microorganisms decompose a portion of the organic fraction of the wastes to CO2 and methane,while the remainder does not appreciably degrade and is considered to be sequestered or stored. The methane and CO2 produced may be collected .m and flared or converted to energy,which oxidizes the methane emitted in the exhaust to CO2. The methane can also be oxidized to carbon dioxide by methanotrophic bacteria in the landfill cover soil. Therefore, the ultimate fate of carbon placed in the landfill is either bw sequestration or in emissions as CH4 or CO2. Management and treatment of waste ultimately leads to management of the method by which the carbon is released back into the environment,similarly changing the climate-related impacts upon the way waste is stored, treated, and disposed. The California Energy Commission estimated that in 2008, '� landfills produced 6.71 million metric tons of CO2e GHG emissions, or 1.4 percent of the