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Coal mine methane: Control, utilization, and abatement 183

before, during, or after mining. Therefore, unlike other GHGs, methane is the primary
component of natural gas and can be converted to usable energy.
Methane is commercially synthesized by the distillation of coal and by heating a
mixture of carbon and hydrogen. It can be produced in the laboratory by heating
sodium acetate with sodium hydroxide and by the reaction of aluminum carbide
(Al 4 C 3 ) with water. Reactions of methane with chlorine and fluorine are triggered
by light.
Environmentally, methane is considered a short-term radiative forcer, meaning
that it has a relatively short (approximately 9–15years) lifespan in the atmosphere.
While methane does not linger as long in the atmosphere as CO 2 , and is emitted in
smaller quantities than CO 2 , its ability to trap heat in the atmosphere or to absorb
the sun’s heat, which is called its global warming potential (GWP), is more than
20 times greater than that of CO 2 [6]. Over the period of its short lifespan, methane
is 84 times more potent as a GHG than CO 2 [7].

10.2.2 Methane emission sources

Methane is mainly emitted during the production and transportation of natural gas, oil,
and coal. Nonetheless, coal mining is not the major source of methane emissions.
CMM from underground mining operations is typically vented or flared; whereas
in surface mining, it is released directly to the atmosphere. However, underground
mining can produce substantially greater levels of CMM than surface mining because
deeper coals are under greater pressure and can hold more methane. Some CMM
remains in the coal after mining and is released by subsequent processing and trans-
portation during postmining activities. CMM emissions from abandoned mines are not
quantified, but may be significant in some cases.
In addition to coal mining, related activities such as the extraction and processing
of natural gas as well as the handling of coal at coal-fired power plants and coal
processing plants result in the release of significant amounts of methane into the atmo-
sphere. Emissions also result from the decay of organic matter in municipal solid
waste landfills, some livestock manure storage systems, and certain agroindustrial
and municipal wastewater treatment systems. However, without more stringent mea-
sures to reduce sources, methane emissions are expected to increase approximately
45% to 8500 million metric tonnes of CO 2 equivalent (MMTCO 2 E) by 2030 [6].
By 2020, global methane emissions from active coal mines alone are estimated to
reach nearly 800 MMTCO 2 E, accounting for less than 10% of total global methane
emissions. China leads the world in estimated CMM emissions with more than 420
MMTCO 2 E (more than 27 billion cubic meters annually) in 2020. Other leading
global CMM emitters are the United States, Russia, Australia, Ukraine, Kazakhstan,
and India [8].

10.2.3 CMM emission models

The flow of methane through coal seams substantially differs from the gas flow mech-
anisms of conventional gas reservoirs. CMM transport in coal has three distinct