Present in the atmosphere, greenhouse gases perform the critical role of keeping the temperature of the earth, by reducing the loss of heat into space. However, if present in excessive amounts, GHG may cause a global warming, the temperature rising to undesirable high levels. Such a climate change is potentially damageable to life.
Emissions of total GHG comprise:
CO2 - carbon dioxide: a colourless, odourless and non-poisonous gas formed by combustion of carbon and in the respiration of living organisms. A peculiarity of the combustion of carbon process is the fact that the weight of CO2 released in combustion exceeds the weight of the fuel burned. Carbon atoms are generally attached to hydrogen atoms. During combustion, carbon combines with oxygen from the air(oxidation). Oxygen being heavier than hydrogen, the output is heavier than the input.
CH4 - methane: present in natural gas, produced by fermentation of organic matter, cattle digestive process, waste dumps, etc.
N2O - nitrous oxide: produced by bacteria in soils (e.g. use of nitrogen fertilizers in agriculture) and oceans.
HFCs - hydrofluorocarbon: compound used in the industry as a refrigerant (e.g. air conditioners), propellant, etc.
PFCs - perfluorocarbons: compound used mainly in the production of aluminium.
SF6 - sulphur hexafluoride: compound used in the industry, typically by the electrical industry.
By emissions one means the release of greenhouse gases into the atmosphere over a specified area and period of time.