Biomass burning, largely resulting from the activities of man, accounts for between 20 and 40 million tonnes of methane emissions each year. Methane emissions arising from biomass burning are a result of incomplete combustion and huge amounts can be produced during large scale burning of woodlands, savanna and agricultural waste.

In savanna regions of the world, burning is often carried out every few years to promote regeneration of the vegetation. The importance of methane emission from biomass burning can be overshadowed by the large amounts of carbon dioxide which are also produced, but in many cases the subsequent regrowth, and carbon dioxide uptake, of previously burned woodland and savanna areas means that the net emission of carbon dioxide is much reduced.

Human Impact

Though fires caused by lightning strikes have, and still do, account for some large biomass burning events, the activities of man in the last 100 years have dwarfed methane emissions from such natural biomass burning. Huge areas of woodland and grassland are now periodically burned for land clearance.

Burning of agricultural waste also produces significant amounts of methane due to its generally high water content. Additionally, wood burning as a domestic fuel source and for charcoal production release significant amounts of methane on a global scale. Accidental fire and arson account for further large scale biomass burning events each year around the world.

Potential for control

The uncontrolled way in which most biomass burning happens means that the only real route to reducing emissions from this source is to reduce the amount of burning itself. Some biomass burning is required if environments such as the savanna are to be retained, but it is the large scale destruction of forest areas for cash crop agriculture and urban spread which stand out as areas to be tackled.

Biomass burning is currently being developed as an alternative to traditional fossil fuel energy production methods, with power stations fuelled by wood chips and the like already a reality. By making use of a renewable resource, like pine wood chips, and avoiding incomplete combustion, these biomass power stations are able to have a much reduced net greenhouse gas impact compared to equivalent coal, oil and gas fired power stations.