Page 217 - Advances In Productive, Safe, and Responsible Coal Mining

196 Advances in Productive, Safe, and Responsible Coal Mining

revenues of typical high-production longwall mines. Additional costs related to CMM
emissions within the mines or into the atmosphere that may be avoided are lost pro-
duction, long- or short-term delays, legal costs, worker’s compensation, punitive
fines, and even mine closure. With CMM recovery now a practical and affordable
way to reduce GHG emissions, improve safety and productivity, and enable coal oper-
ators to profit from on- or off-site CMM utilization, what was once a waste product
and solely a miner’s curse is now a valuable byproduct, provided that it can be prop-
erly controlled and managed.
In evaluating the economics of CMM recovery, it must be recognized that in order
to establish a new drainage system in a mine, a major investment is required to cover
cost items such as the CMM extraction plant, surface facilities, drilling, piping,
pumping, installation of drainage equipment, and on-line monitoring systems.
Although capital costs for CMM are somewhat less than those for CBM, they are still
substantial and depend on a number of factors, including depth of mining, distance
between mining districts to extraction plants, technical layout (such as pipe diameters,
optimal borehole spacing, etc.), method of monitoring and control, and site-specific
geological and mining conditions [24].
In the case of VAM, local electricity sales prices and persuasive governmental sup-
port may be the determining factor for economical feasibility of generating electricity
from VAM. In cases where CMM or VAM cannot be economically recovered and
used due to impractical site-specific conditions or unattractive markets, it may be pos-
sible to generate revenue from carbon credits through destroying CMM or VAM by
converting CH 4 to CO 2 .

10.7 Conclusion

CMM is stored within coal as a result of the coalification process whereby plant mate-
rial is converted to coal. Due to coal-mining activities, pore pressure decreases and
trapped methane is released from the coal and surrounding rock strata into the mining
atmosphere. This leads to the build-up of CMM in mines, which potentially creates an
explosive hazard. Ventilation or degasification systems are used to prevent CMM
accumulation and to ensure its release to the atmosphere for safety reasons. CMM
is therefore both a safety hazard and a potent GHG. On the other hand, CMM has
the potential benefit of being used as a clean fuel.
The main technique for controlling CMM concentrations is ventilation. Despite
low concentrations of methane in vented mine air, collectively VAM is the single larg-
est source of CMM emissions globally. In order to prevent emissions into the atmo-
sphere, VAM released through ventilation shafts can either be destroyed by converting
CH 4 to CO 2 (e.g., flaring), or be captured and compressed for commercial uses
(e.g., electricity generation).
CMM can be drained prior to, during, and even after mining operations in order to
mitigate any unwanted disasters within the mine and reduce environmental concerns
with regard to GHG. Recovered CMM is most often used for power generation,