Methane emissions from worldwide increasing abandoned
coal mines
have posed multiple challenges of global warming, energy waste, and
explosion risk. This study first profiles the dynamic patterns of
coal mine methane emissions in different recovery technologies, methane
extraction with drainage (MEWD, mine-water concurrently extracted
and treated) and direct methane extraction (DME, noncontrol on mine-water),
in two abandoned mines from Ningxia and Inner Mongolia as China’s
leading coal provinces. Then, we conducted a techno-economic analysis
and life-cycle assessment to quantify their comprehensive benefits.
The key findings are as follows: (1) MEWD can long recover methane,
although the economic profits decrease with declining methane extraction
volume. DME can only work for ∼5 years, after which the mine
is flooded, where methane is sealed underground and not recoverable.
(2) MEWD drains and further treats the mine-water with an additional
29.4–35.9 million CNY cost compared with DME, while MEWD can
achieve greater life-cycle environmental benefits with more cumulative
methane recovery, whose CO2-eq (GWP-100) and SO2 reductions are 64.4 and 53.4% higher than those of DME. (3) MEWD
is more promising for large-scale implementation, where feed-in tariffs
and carbon market measures can improve the economics for sustainable
management of incremental abandoned mine methane.
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