Energy Penalty Versus Climate Benefit from Ventilation Air Methane Oxidation in Regenerative Thermal Oxidizers: A Life-Cycle Assessment Under Variable Methane Concentrations

Ventilation air methane (VAM) oxidation in regenerative thermal oxidizers (RTOs) can substantially reduce greenhouse gas (GHG) emissions from underground coal mines, but its environmental effectiveness depends on the operational energy demand. This study evaluates the trade-off between climate benefits and energy penalty using a life-cycle assessment (LCA) approach. Three methane concentration scenarios (0.1, 0.326, 0.5 vol.% CH4) representing different operating regimes were analyzed. Environmental performance showed strong concentration-dependent response associated with the transition from non-autothermal to autothermal operation. Under autothermal conditions (0.326 and 0.5 vol.% CH4), life-cycle GHGs were reduced by approximately 90% compared with direct methane release. At 0.1 vol.% CH4, substantial auxiliary heating was required, which decreased the net climate benefit. Electricity consumption during operation was a major determinant of the environmental footprint of the system. The results indicate that methane concentration is an important parameter and should be considered together with energy demand and mine-safety constraints when assessing VAM mitigation systems.