Mitigating Ventilation Air Methane Cost-Effectively from a Colliery in Australia

Methane has been controlled in collieries in the past only for safety and statutory compliance reasons; however concerns over greenhouse gas emissions mean that this is now changing. About 65% of greenhouse emissions associated with underground coal mining come from ventilation air methane (VAM). The machinery to mitigate these fugitive emissions once the VAM exits the mine fans is expensive, has safety concerns and is not widely used at present. Consider these factors; more collieries are mining lower seams, methane content increases with depth, VAM mitigation plants are not widely used, most mine emissions are VAM, and widespread concern over greenhouse gases mean that it is desirable to lower VAM emissions now. One solution would be a method to prevent more methane from entering the mine airstream and becoming VAM in the first place. Recently, in a colliery in the Hunter Valley, this mitigation method underwent a 12-month trial, and involved six different measures. Measurements were taken to assess the emissions mitigation which was achieved, and the cost of the works; all the results are detailed herein. A reduction in fugitive emissions of 80,307 t/CO2-e below that which was projected for the next 12-month period was quantified, at an average cost of A$1.28c t/CO2-e. The mitigation measure outlined here represent a first attempt to the author’s knowledge, in an operating mine, to lower a collieries’ environmental footprint by preventing methane from entering the mine airstream and becoming VAM gas by the deliberate use of mitigation measures.