Methane is often vented to the atmosphere in the degassing of coal mines.
Technologies to economically recover methane for fuel use, which could reduce
emissions by 30-90% (IPCC-TP-1, 1996), have been developed and are commercially
available. Pre-mining degasification or enhanced recovery using vertical or
horizontal in-mine boreholes can economically recover methane produced via drainage
(which represents 30% of all coal mine methane). Nevertheless, the major fraction
(70%) is produced via the ventilation systems and being very dilute (< 1%
in air) is presently vented (US EPA, 1993). Technology should focus on the utilisation
of this dilute stream. Estimate for equivalent CO2
emission reduction by recovering and utilising CH4
from one mine reaches 1 TgC/year. Capturing all CH4
from coal mine and burning is estimated to have the potential to reduce greenhouse
gases by about 5% of the CO2 emitted from coal
burning (APEC, 1997).