Improved estimation methods for surface coal mine methane emissions for reporting, beneficial use, and emission reduction purposes and relative to Australia's safeguard mechanisms

Methane is responsible for 30% of global warming, with coal mining contributing 31% of 2023 methane emissions in the energy sector. Australia's Bowen Basin is the largest metallurgical coal (MC) producing region with a need to reduce fugitive coal mine methane (CMM) emissions, most notably from surface coal mining operations, as underground mines have increased pre-drainage with flaring or beneficial use. Australia's regulatory framework is moving to mine-specific models, based on measured data and reservoir modelling, to evaluate CMM emissions more effectively and quantify the benefit of projects that reduce emissions.

This paper highlights the definitions, classifications, and determinations in the Australian Safeguard Mechanisms to define surface mining and underground CMM emissions. While underground mining has a broad range of potential mitigation strategies, open-cut MC mine mitigation strategies are more limited and will be the focus of this paper. Australian-specific open-cut MC mine examples will illustrate the potential reductions in emissions and positive cash-flow benefits possible by implementing pre-drainage and new technologies (e.g., subterranean barriers).

Six CMM scenarios, based on representative data from Australia's Bowen Basin coal mines and typical beneficial use strategies, show that a typical pre-drainage strategy at a surface mine can reduce CMM emissions by 38% without any further beneficial use of produced gas. Further, implementing a pre-drainage strategy with subterranean barriers can reduce emissions by 46%, a 10% improvement over pre-drainage alone. The emissions estimation methodology proposed can be applied to other carbon pricing frameworks and regions to define the impacts and benefits of implementing emissions reduction strategies.