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Air Quality and Greenhouse Gas Technical Report Griffith Energy Storage Project
<br /> 3.0 GREENHOUSE GAS EMISSIONS
<br /> 3.1 ENVIRONMENTAL SETTING
<br /> 3.1.1 The Greenhouse Effect
<br /> Certain gases in the earth's atmosphere, classified as GHGs, play a critical role in determining the earth's
<br /> surface temperature. A GHG is any gas in the atmosphere that absorbs infrared radiation. As solar
<br /> radiation enters the earth's atmosphere, a portion of the radiation is absorbed by the earth's surface, and
<br /> a portion is reflected back through the atmosphere into space. The absorbed radiation is eventually
<br /> emitted from the earth into the atmosphere, not as solar radiation, but as infrared radiation. Most solar
<br /> radiation passes through GHGs; infrared radiation is selectively absorbed or"trapped" by GHGs as heat
<br /> and then reradiated back toward the earth's surface, warming the lower atmosphere and the earth's
<br /> surface. This phenomenon, known as the "greenhouse effect," is beneficial for maintaining a habitable
<br /> climate on the earth. As the atmospheric concentrations of GHGs rise, however, the average temperature
<br /> of the lower atmosphere gradually increases, thereby increasing the potential for indirect effects such as
<br /> a decrease in precipitation as snow, a rise in sea level, and changes to plant and animal species and
<br /> habitat.
<br /> Whereas pollutants with localized air quality effects have relatively short atmospheric lifetimes (about one
<br /> day), GHGs have long atmospheric lifetimes (one year to several thousand years). GHGs persist in the
<br /> atmosphere long enough to be dispersed globally. Although the exact lifetime of any particular GHG
<br /> molecule depends on multiple variables and cannot be pinpointed, scientific evidence reveals that more
<br /> CO2 is emitted into the atmosphere than is sequestered by ocean uptake, vegetation, and other forms of
<br /> sequestration. Of the total annual human-caused CO2 emissions, approximately 54 percent is
<br /> sequestered through ocean uptake, uptake by northern hemisphere forest regrowth, and other terrestrial
<br /> sinks within a year, whereas the remaining 46 percent of human-caused CO2 emissions remains stored in
<br /> the atmosphere. The quantity of GHGs that it takes to ultimately result in climate change is not known
<br /> precisely, although scientific evidence strongly indicates no single project would be expected to contribute
<br /> measurably to a noticeable incremental change in the global average temperature.
<br /> 3.1.2 Greenhouse Gases and Global Warming Potential
<br /> GHGs are emitted by natural processes and human activities. Natural GHG sources include
<br /> decomposition of dead organic matter; respiration of bacteria, plants, animals, and fungus; evaporation
<br /> from oceans; and volcanic outgassing. Human activities known to emit GHGs include industrial
<br /> manufacturing, utilities, transportation, residential, and agricultural activities. The GHGs that enter the
<br /> atmosphere because of human activities are CO2, CH4, N20, fluorinated carbons (hydrofluorocarbons
<br /> (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6).
<br /> CO2 is an odorless, colorless gas with both natural and anthropogenic sources. Examples of natural
<br /> sources are respiration of bacteria, plants, and animals, evaporation from oceans, and decomposition of
<br /> organic matter. Human activities that emit CO2 include burning coal, oil, natural gas, and wood.
<br /> CH4 is a flammable gas that is the main component of natural gas. When burned in the presence of
<br /> oxygen, CO2 and water are released. There are no direct health effects from exposure to CH4. Sources of
<br /> CH4 include decay or organic material, natural gas fields, cattle, and landfills.
<br /> N20 is a colorless gas that can cause euphoria, dizziness, and slight hallucinations when exposed to
<br /> higher concentrations. Sources include agricultural sources (e.g., microbial processes in soil and water,
<br /> fertilizer) and industrial processes (e.g., fossil fuel-fired power plants, vehicle emissions, nylon
<br /> production).
<br /> OTETRA TECH 30 July 2023
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