Exploring the bounds of methane catalysis in the context of atmospheric methane removal

Abstract

Methane, a potent greenhouse gas, is a significant contributor to global warming, with future increases in its abundance potentially leading to an increase of more than 1◦C by 2050 beyond other greenhouse gases if left unaddressed. To remain within the crucial target of limiting global warming to 1.5◦C, it is imperative to evaluate the potential of methane removal techniques. This study presents a scoping analysis of different catalytic technologies (thermal, photochemical and electrochemical) and materials to evaluate potential limitations and energy requirements. An analysis of mass transport and reaction rates is conducted for atmospheric methane conversion system configurations. For the vast majority of catalytic technologies, the reaction rates limit the conversion which motivates future efforts for catalyst development. An analysis of energy requirements for atmospheric methane conversion shows minimum energy configurations for various catalytic technologies within classic tube or parallel plate architectures that have analogs to ventilation and industrial fins. Methane concentrations ranging from 2 ppm (ambient) to 1000 ppm (sources, such as wetlands, fossil-fuel extraction sites, landfills etc.) are examined. The study finds that electrocatalysis offers the most energy efficient approach (∼0.2 GJ/tonne CO2e) for new installations in turbulent ducts, with a total energy intensity <1 GJ/tonne CO2e. Photocatalytic methane removal catalysts are moderately more energy intensive (∼2 GJ/tonne CO2e), but could derive much of their energy input from “free” solar energy sources. Thermal systems are shown to be excessively energy intensive (>100 GJ/tonne), while combining photovoltaics with electrochemical catalysts (∼1 GJ/tonne CO2e) have comparable energy intensity to photocatalytic methane removal catalysts.