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Coal mine methane: Control, utilization, and abatement 195

disorders usually observed in coal miners include pneumoconiosis, lung cancer,
chronic obstructive pulmonary disorder, and asthma [3].
Thermal oxidation technologies have been introduced at commercial scales to
abate VAM emissions or utilize VAM to produce electricity. However, current
VAM technologies are generally not able to process methane concentrations below
0.2% without use of additional fuel to augment the methane content. Other technol-
ogies to mitigate VAM emissions include catalytic oxidation, lean fuel combustion,
and rotary kilns. These are emerging and under development [1]. In some countries
like the United States and Australia, VAM is recovered in commercial scale using
either a thermal or catalytic oxidation technique that produces no flame, yet in addi-
tion to abating VAM emissions, they can produce thermal energy or electricity using a
steam turbine. Although VAM is generally less than 2%, it is possible to produce elec-
tricity at concentrations more than 0.5% by circulating water through the oxidizer and
capturing superheated steam, which may be used to power a steam turbine.
Increasing atmospheric concentrations of methane will have important implica-
tions for global climate and perhaps for the stratospheric ozone layer and background
levels of tropospheric ozone. In fact, the GWP of CH 4 is at least 84 times greater than
CO 2 over a 20-year period. However, the GWP decreases to around 25 times greater
when calculated over a 100-year period. CMM drainage systems are an effective way
of reducing CMM from mining operations. The 200-plus CMM recovery and utiliza-
tion projects described earlier also serve as key abatement strategies worldwide. For
instance, one underground coal mine in the United States employing a CMM drainage
system will reduce emissions by more than 453,500 metric tonnes/year CO 2 equiva-
lent, which equates to taking approximately 100,000 cars off the road [22].

10.6 Economics of CMM recovery

Key factors that may affect the economics of CMM recovery are: (i) quantity and qual-
ity of CMM, (ii) capital and operating costs of the project, (iii) elasticity of demand
and selling price for recovered CMM, and (iv) availability of environmental benefits
and credits. Although the economical analysis of CMM recovery is case based, pre-
liminary cost-effective analyses indicate that under certain conditions, methane recov-
ery is economically attractive to the mining industry. In addition, there are some
environmental benefits to abating methane as doing so will reduce the amount of
GHGs. Despite many efforts to put a price on carbon, as yet there are no quantifiable
economic numbers associated with these environmental benefits.
Boger et al. [23] indicated three primary reasons for recovering CMM:
(i) decreasing explosions within underground coal mines and consequently increasing
mine safety, (ii) improving mine economics due to using or selling CMM as a
byproduct and reduce production delays, and (iii) mitigating global and local environ-
mental risks associated with carbon emissions.
Effective CMM drainage reduces the risk of explosions and gas outbursts, venti-
lation costs, and unwanted accidents, and miners’ diseases. Reducing these risks in
turn diminishes their associated costs, which can usually impose high losses in