First thing I need to come clean, I didn’t write this blog, the words all come from Canada’s National Inventory Report (NIR) which documents Canada’s annual GHG emissions estimates to the UN. The report’s very interesting, but dense reading, and thought that this section was an excellent description that I certainly learnt from, so wanted to share. The full report can be found here: https://unfccc.int/documents/461919 The quoted information is on page 35-36 if you want to read in situ.
The Greenhouse Gases are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), perfluorocarbons (PFCs), hydrofluorocarbons (HFCs), sulphur hexafluoride (SF6) and nitrogen trifluoride (NF3).
Carbon Dioxide
CO2 is a naturally occurring, colourless, odourless, incombustible gas formed during respiration, combustion, decomposition of organic substances, and the reaction of acids with carbonates. It is present in the Earth’s atmosphere at low concentrations and acts as a GHG. The global carbon cycle is made up of large carbon flows and reservoirs. Through these, CO2 is constantly being removed from the air by its direct absorption into water and by plants through photosynthesis and, in turn, is naturally released into the air by plant and animal respiration, decay of plant and soil organic matter, and outgassing from water surfaces. Small amounts of CO2 are also injected directly into the atmosphere by volcanic emissions and through slow geological processes such as the weathering of rock (Hengeveld et al., 2005). Although human-caused releases of CO2 are relatively small (1/20) compared to the amounts that enter and leave the atmosphere due to the natural active flow of carbon (Hengeveld et al., 2005), human influences now appear to be significantly affecting this natural balance. This is evident in the measurement of the steady increase of atmospheric CO2 concentrations since pre-industrial times across the globe (Hengeveld et al., 2005). Anthropogenic sources of CO2 emissions include the combustion of fossil fuels and biomass to produce energy, building heating and cooling, transportation, land-use changes including deforestation, the manufacture of cement, and other industrial processes.
Methane
CH4 is a colourless, odourless, flammable gas and is the simplest hydrocarbon. CH4 is present in the Earth’s atmosphere at low concentrations and acts as a GHG. CH4 usually in the form of natural gas, is used as feedstock in the chemical industry (e.g., hydrogen and methanol production), and as fuel for various purposes (e.g., heating homes and operating vehicles). CH4 is produced naturally during the decomposition of plants or organic matter in the absence of oxygen and is released from wetlands (including rice paddies) and through the digestive processes of certain insects and animals, such as termites, sheep and cattle. CH4 is also released from industrial processes, fossil fuel extraction, coal mines, incomplete fossil fuel combustion, and waste decomposition in landfills.
Nitrous Oxide
N2O is a colourless, non-flammable, sweet-smelling gas that is heavier than air. Used as an anaesthetic in dentistry and surgery, as well as a propellant in aerosol cans, N2O is most commonly produced via the heating of ammonium nitrate (NH4NO3). It is also released naturally from oceans, by bacteria in soils, and from animal wastes. Other sources of N2O emissions include the industrial production of nylon and nitric acid, combustion of fossil fuels and biomass, soil cultivation practices, and the use of commercial and organic fertilizers.
Perfluorocarbons
PFCs are a group of human-made chemicals composed of carbon and fluorine only. These powerful GHGs were introduced as alternatives to ozone-depleting substances (ODSs), such as chlorofluorocarbons (CFCs) in manufacturing semiconductors. PFCs are also used as solvents in the electronics industry and as refrigerants in some specialized refrigeration systems. In addition to being released during consumption, they are emitted as a by-product during aluminium production.
Hydrofluorocarbons
HFCs are a class of human-made chemical compounds that contain only fluorine, carbon and hydrogen, and are powerful GHGs. As HFCs do not deplete the ozone layer, they are commonly used as replacements for ODSs such as CFCs, hydrochlorofluorocarbons (HCFCs) and halons in various applications including refrigeration, fire-extinguishing, semiconductor manufacturing and foam blowing.
Sulphur hexafluoride
SF6 is a synthetic gas that is colourless, odourless, and non-toxic, except when exposed to extreme temperatures. It acts as a GHG due to its very high heat-trapping capacity. SF6 is primarily used in the electricity industry as insulating gas for high-voltage equipment. It is also used as a cover gas in the magnesium industry to prevent oxidation (combustion) of molten magnesium. In lesser amounts, SF6 is used in the electronics industry in the manufacturing of semiconductors and as a tracer gas for gas dispersion studies in industrial and laboratory settings.
Nitrogen Trifluoride
NF3 is a colourless, non-flammable gas that is used in the electronics industry as a replacement for PFCs and SF6. It has a higher percentage of conversion to fluorine—the active agent in the industrial process—than PFCs and SF6 for the same amount of electronics production. It is used in the manufacture of semi-conductors, liquid crystal display (LCD) panels and photovoltaics. NF3 is broken down into nitrogen and fluorine gases in situ, and the resulting fluorine radicals are the active cleaning agents that attack the poly-silicon. NF3 is further used in hydrogen fluoride and deuterium fluoride lasers, which are types of chemical lasers (UNFCCC, 2010)
Hope you enjoyed the background info!
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