Global warming, climate change, ozone depletion, sea level rise, biodiversity are all affected, one way or another, directly or directly, by harmful 'greenhouse' gases.
A number of human activities, processes and consumptions produce waste gases that are harmful to the environment. They include:
Manufacturing industries and construction
Fugitive emissions from fuels
Oil and natural gas
Production of halocarbons and sulphur hexafluoride
Consumption of halocarbons and sulphur hexafluoride
Solvent and other product use
Prescribed burning of savannas
Field burning of agricultural residues
Solid waste disposal on land
Much of these harmful gases, natural and man-made, were targeted for reduction during the recently concluded COP3 conference in Kyoto. A brief description and effects of six gases are given below:
CO2 emissions from fuel burning, responsible
for about 87 percent of global warming, have
increased by about 27 percent since the
Global warming potential: 25,000 times that of
Carbon dioxide (CO2):
A naturally occurring gas produced by living organisms and fermentation, CO2 is also produced by the combustion of carbonaceous fuels. A normal component of the breath we exhale, it is hazardous in concentrated volumes.
Nitrous Oxide (N2O):
naturally occurring from microbial action in soil, N20 is also produced by fuel burning. Scientists say its production is increased by the use of nitrogen based fertiliser in agriculture, as well as by the use of catalytic converters in automobiles.
A naturally occurring, flammable gas, methane is caused by geological coal formations and by the decomposition of organic matter. Leading man-related sources are landfills; livestock digestive processes and waste, especially ruminants (cud-chewing animals); and wetland rice cultivation.
Hydrofluorocarbon gases (HFC) :
Man-made specialty gases developed as an alternative to ozone-eating chlorofluorocarbons (CFC), the coolant, cleaning, and propellant gases were blacklisted internationally in 1987. Because they do not possess chlorine, HFCs do not directly destroy ozone in the earth's atmosphere. They do, however, contribute to global warming. Principle uses: refrigeration; as agents used to blow foams or insulation; solvents or cleaning agents, especially in semi-conductor manufacturing.
Perfluorocarbons (PFC), or Perfluorocompounds:
Man-made replacement gases for CFCs but result also as a by-product of aluminium smelting. PFCs also used as a purging agent for semi-conductor manufacture and small amounts are produced during uranium enrichment processes.
Sulphur Hexafluoride (SF6):
Very low atmospheric concentration makes it an ideal test gas for gas concentration monitors. Principle uses: insulating material for high-voltage equipment like circuit breakers at utilities. Also used in water leak detection for cable cooling systems. SF6 is a man-made gas.
Sources: U.S. Energy Intelligence Agency, International Energy Agency, Intergovernmental Panel on Climate Change.
CO2 emissions from fuel burning, responsible for about 87 percent of global warming, have increased by about 27 percent since the industrial revolution.
Global warming potential: 25,000 times that of CO2.
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