Transitioning from emission source to sink: Economic and environmental trade-offs for CO2-enhanced coalbed methane recovery of Mannville coal Canada.

Economically viable and environmentally sustainable geological carbon sequestration (GCS) will be necessitated to mitigate the rising climate change. CO2-enhanced coalbed methane (CO2-ECBM) recovery offers a promising solution to address the dual challenges in energy security and environmental sustainability. However, scaling up CO2-ECBM requires comprehensive multi-perspective understanding at the system level. This work proposes an engineering, economic, and environmental (3E) system analysis framework to evaluate the multi-aspect benefits of CO2-ECBM, deploying the Mannville coal in Alberta, Canada, as an example. Four key findings are highlighted. First, we demonstrated deep unmineable coal seams are reliable CO2 sinks in that 0.08 kg of CO2 can be stored per MJ of CBM production. Second, the levelized cost is $1.19/GJ with a carbon footprint of ∼10 gCO2e/MJ using current technologies. GCS in coal enables carbon offsets due to CO2 utilization. Third, carbon-neutral and carbon-negative CBM is achievable when CO2 is point-sourced and from atmosphere, respectively. Lastly, the carbon dioxide removal (CDR) during CO2-ECBM can generate a trade-off of $4.7/GJ associated with 8.6 g CDR (a net CDR efficiency of 6.2 %). Economic viable CDR requires a carbon tax of $175/tCO2 plus reducing direct air capture (DAC) costs to $115/tCO2 or improving DAC efficiency to at least 86 %. This novel integrated framework bridges the gap between energy engineers, economists, and policymakers, unlocking the potential to transform unmineable coal seams from a CO2 source to a sink.