Global warming and greenhouse gasses:
The earth is surrounded by a cover of gasses as atmosphere. This atmosphere allows most of the light to pass through, which reaches the surface of earth. This light from sun is absorbed by the earth surface and converts into heat energy. This heat energy is re-emitted by the surface of the earth during night. Due excessive presence of some gasses in the atmosphere, this escape of heat from earth surface is prevented, resulting in heating of earth called ‘global warming’. The gasses which are responsible for causing global warming are called ‘greenhouse gasses’.
The harmful effects of presence of greenhouse gasses in atmosphere are global warming, climate change, ozone depletion, sea level rise, adverse effects on biodiversity etc. One way or another these adverse impacts are all directly or directly related to the presence of greenhouse gases in the atmosphere. A number of human activities, processes and consumptions produce waste gasses or greenhouse gasses that are harmful to the environment. They include:
(a) Fuel combustion
(b) Energy industries
(c) Manufacturing industries and construction
(d) Vehicle Transport and automobiles
(e) Fugitive emissions from fuels
(f) Burning of solid fuels
(g) Use of oil and natural gas
(h) Mineral products
(i) Chemical industry
(j) Metal production
(k) Production of halocarbons and sulfur hexafluoride
(l) Consumption of halocarbons and sulfur hexafluoride
(m) Solvent and other product use
(n) Enteric fermentation
(o) Manure management
(p) Rice cultivation
(q) Agricultural soils
( r) Prescribed burning of savannas
(s) Field burning of agricultural residues
(t) Solid waste disposal on land
(u) Wastewater handling
(v) Waste incineration
Much of these harmful gases are produced either naturally or by various human activities; which we should reduce. Brief description and effects of six important greenhouse gases are given below:
Carbon dioxide (CO2) - A naturally occurring gas produced by living organisms and fermentation. It is a normal component of the breath we exhale; it is hazardous in concentrated volumes. Large quantity of carbon dioxide is produced by the combustion of carbonaceous fuels. Carbon dioxide emissions from fuel burning, responsible for about 87 percent of global warming, have increased by about 27 percent since the industrial revolution.
Nitrogen oxides (NOx) – Nitrogen oxides are naturally occurring from microbial action in soil. NOx is also produced by fuel burning. Scientists say its production is increased by the use of nitrogen based fertilizers in agriculture, as well as by the use of catalytic converters in automobiles.
Methane (CH4) – Methane is a naturally occurring, in-flammable gas. Methane is produced by geological coal formations and by the decomposition of organic matters. Leading man-related sources of methane are landfills; livestock digestive processes and waste, especially ruminants (cud-chewing animals); and wetland rice cultivation.
Hydroflurocarbon gasses (HFCs) - Chlorofluorocarbons (CFC), the coolant, cleaning, and propellant gases were blacklisted internationally due to its ozone-eating characteristics. HFCs do contribute to global warming. Global warming potential of HFCs is 4,000 to 10,000 times that of CO2.
Perfluorocarbons (PFC), or perflurocompounds - 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. Global warming potential of Perfluorocarbons (PFC), or perflurocompounds is 6,000 to 10,000 that of CO2.
Sulfur 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.