Background
As organic wastes decompose anaerobically within a landfill, a gaseous mixture of methane and carbon dioxide in roughly equal parts is produced. This 'landfill gas' was only recognised as a pollutant - and one with the potential to explode - relatively recently, and in devising ways of controlling the gas, many landfill sites have installed landfill gas recovery systems which either simply flare off the gas to dispose of it or alternatively utilise the gas for electricity production or heat generation.
Incidence
Landfills were the number one source of Canadian emissions of methane in 1990 - 38% of a total of 3.7 megatonnes.