methane

Simplest hydrocarbon of the alkane series. Colourless, odourless, and lighter than air, it burns with a bluish flame and explodes when mixed with air or oxygen. As the chief constituent of natural gas, methane's main use is as a fuel. It also occurs in the explosive firedamp of coal mines. Methane emitted by rotting vegetation forms marsh gas, which may ignite by spontaneous combustion to produce the pale flame seen over marshland and known as will-o'-the-wisp.

Methane causes about 38% of the warming of the globe through the greenhouse effect; weight for weight it is 60–70 times more potent than carbon dioxide at trapping solar radiation in the atmosphere and so heating the planet. The rate of increase of atmospheric methane is declining and global emissions remained relatively constant over the period 1984–96, so atmospheric levels were predicted, in 1998, to stabilize by the 2020s. An estimated 15% of all methane gas in the atmosphere is produced by cattle and other cud-chewing animals, and 20% is produced by termites that feed on soil.

Research reported in 2006 revealed that plants may also release methane.