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4.5 – Greenhouse Gas Emissions
<br />Draft Environmental Impact Report February 2021
<br />14800 W. Schulte Road Logistics Center 4.5-2
<br />Greenhouse Gas
<br />A GHG is any gas that absorbs infrared radiation in the atmosphere; in other words, GHGs trap heat in the
<br />atmosphere. As defined in California Health and Safety Code, Section 38505(g), for purposes of administering many
<br />of the state’s primary GHG emissions reduction programs, GHGs include carbon dioxide (CO 2), methane (CH4),
<br />nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), and nitrogen
<br />trifluoride (NF3) (see also California Environmental Quality Act [CEQA] Guidelines, Section 15364.5). Some GHGs,
<br />such as CO2, CH4, and N2O, occur naturally and are emitted into the atmosphere through natural processes and
<br />human activities. Of these gases, CO2 and CH4 are emitted in the greatest quantities from human activities.
<br />Manufactured GHGs, which have a much greater heat-absorption potential than CO2, include fluorinated gases,
<br />such as HFCs, PFCs, and SF6, which are associated with certain industrial products and processes. The following
<br />paragraphs provide a summary of the most common GHGs and their sources.1
<br />Carbon Dioxide. CO2 is a naturally occurring gas and a by-product of human activities and is the principal
<br />anthropogenic GHG that affects the Earth’s radiative balance. Natural sources of CO 2 include respiration of bacteria,
<br />plants, animals, and fungus; evaporation from oceans; volcanic out -gassing; and decomposition of dead organic
<br />matter. Human activities that generate CO2 are from the combustion of fuels such as coal, oil, natural gas, and
<br />wood and changes in land use.
<br />Methane. CH4 is produced through both natural and human activities. CH 4 is a flammable gas and is the main
<br />component of natural gas. CH4 is produced through anaerobic (without oxygen) decomposition of waste in landfills,
<br />flooded rice fields, animal digestion, decomposition of animal wastes, production and distribution of natural gas
<br />and petroleum, coal production, and incomplete fossil fuel combustion.
<br />Nitrous Oxide. N2O is produced through natural and human activities, mainly through agricultural activities and natural
<br />biological processes, although fuel burning and other processes also create N2O. Sources of N2O include soil
<br />cultivation practices (microbial processes in soil and water), especially the use of commercial and organic fertilizers,
<br />manure management, industrial processes (such as in nitric acid production, nylon production, and fossil-fuel-fired
<br />power plants), vehicle emissions, and using N2O as a propellant (e.g., rockets, racecars, and aerosol sprays).
<br />Fluorinated Gases. Fluorinated gases (also referred to as F-gases) are synthetic powerful GHGs emitted from many
<br />industrial processes. Fluorinated gases are commonly used as substitutes for stratospheric ozone-depleting
<br />substances (e.g., chlorofluorocarbons [CFCs], hydrochlorofluorocarbons [HCFCs], and halons). The most prevalent
<br />fluorinated gases include the following:
<br />•Hydrofluorocarbons: HFCs are compounds containing only hydrogen, fluorine, and carbon atoms. HFCs are
<br />synthetic chemicals used as alternatives to ozone-depleting substances in serving many industrial,
<br />commercial, and personal needs. HFCs are emitted as by-products of industrial processes and are used
<br />in manufacturing.
<br />•Perfluorocarbons: PFCs are a group of human-made chemicals composed of carbon and fluorine only.
<br />These chemicals were introduced as alternatives, with HFCs, to ozone-depleting substances. The two main
<br />sources of PFCs are primary aluminum production and semiconductor manufacturing. Because PFCs have
<br />stable molecular structures and do not break down through the chemical processes in the lower
<br />atmosphere, these chemicals have long lifetimes, ranging between 10,000 and 50,000 years.
<br />1 The descriptions of GHGs are summarized from the Intergovernmental Panel on Climate Change (IPCC) Second Assessment
<br />Report (1995), IPCC Fourth Assessment Report (2007), CARB’s “Glossary of Terms Used in GHG Inventories” (2021), and EPA’s
<br />“Glossary of Climate Change Terms” (2016).
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