Coal | Oil
The bulk of energy related methane emissions arise from methane
release during fossil fuel extraction and transportation. Some methane
is also produced during fossil fuel combustion, with sources such
as fossil fuelled power stations, transport and heating all being
significant contributors to atmospheric methane concentrations.
The total global methane emission estimate from energy related sources
is around 100 million tonnes each year.
At 30-50 million tonnes of methane emission per year coal mining
remains a big source of man-made methane, despite the decline of
coal mining here in the UK. The bulk of global methane emissions
come from only a few relatively deep mines around the world.
During the geological process of coal formation methane is formed
and some of this then remains trapped until released by mining operations.
Generally, the deeper the coal seam, the greater the amounts of
methane that are trapped. In shallow and open cast mines, the trapped
methane is often released directly to the atmosphere during mining.
In deeper mines the methane is often released via ventilation shafts
to prevent potentially dangerous methane concentrations building
Strategies to reduce methane emissions from coal mines include
recovery of coal mine methane both during construction, use and
afterwards. Such recovery can be economically viable, particularly
in deep mines, given sufficient quantities of methane, and can substantially
reduce emissions to the atmosphere.
As with coal, the geological formation of oil can result in large
methane deposits associated with the oil. During oil drilling and
extraction, the trapped methane is released to the atmosphere. Targeted
collection of the methane associated with oil can vastly reduce
emissions from this source, with the collected methane being flared
off as carbon dioxide or even providing an additional fuel source.
The loss of methane during natural gas extraction is obviously
something which has both a direct greenhouse gas and an economic
cost. Nevertheless, significant amounts of methane are lost during
both extraction and transfer of methane above ground. It is estimated,
for example, that in the 1990's around 6 percent of the methane
piped across Russia was lost due to leaks. More efficient collection
techniques, improved targeting of buried methane deposits and better
maintained transfer pipelines could all help reduce incidental methane
emissions from this source.