Removal of Methane from Mine Ventilation Air by Biofiltration

This project examined the feasibility of biofiltration technology, using coal as the support medium, for removing methane from mine ventilation air (MVA). A laboratory-scale biofiltration system was designed and packed with coal from Appin Colliery. The extent and robustness of methane removal from an inlet gas stream containing 1 v/v% methane in humid air was assessed under varying operating conditions.

The study established for the first time that a coal-packed biofilter is capable of removing methane from air. Most significantly, microbes that are already on the coal at the mine site catalysed this removal. This means inoculation with a laboratory grown culture of microbes, as investigated in a parallel run, is not necessary. The results also suggest initial conditioning of the coal bed via nutrient addition may be needed to allow multiplication of the microbes inherent on the coal and provide successful biofilter operation. The conditioning extent and associated time-frame is yet to be ascertained. Once the microbial community is established it can operate with minimal supervision.

The next important steps for research are to calculate cost/benefit estimates and to evaluate biofilter robustness towards fluctuations in MVA methane concentration as well as seasonal temperature to the extent these can occur at Australian mine sites.

The findings indicate methane in MVA can be oxidised by microbes inherent in coal when the coal is used as a packing material. Under the conditions used in this work, biofiltration technology may find application in circumstances where partial methane elimination of comparatively low MVA flows is acceptable. Conversely, complete methane oxidation or utilising the technology at sites possessing high gas flow rates will necessitate an increasingly larger biofilter volume which will decrease its viability.