Assessing the potential benefits of methane oxidation technologies using a concentration-based framework

Abstract

Lowering the atmospheric methane concentration is critical to reducing short-term global warming because of methane’s high radiative forcing and relatively short lifetime. Methane could be destroyed at its emissions sources or removed from the atmosphere by oxidizing it to carbon dioxide and water vapor, greatly lowering the warming effect. Here we provide, to the best of our knowledge, the first estimate of the amount of methane that is emitted at a given concentration. We use this to assess the potential benefits (global temperature, air quality, and economic) of various technologies that could oxidize methane above specific concentration thresholds. We estimate that global mean surface temperature could be reduced by 0.2 ± 0.1 ℃ by continuously oxidizing all anthropogenic methane emitted above 1,000 parts per million (the lowest concentration addressable with current commercial technologies). Continuously oxidizing all methane currently emitted above 10 parts per million could cause 0.4 ± 0.2 °C of cooling. For the economic benefit of removing atmospheric methane to outweigh the associated energy cost, we show that reactors that use heat to oxidize methane must operate at most 3 ± 2 ℃ above ambient temperature while those that use light must convert at least 9 ± 8 % of photons into oxidized methane molecules. Our framework can be used by scientists, engineers, and policymakers to better understand the connections between methane sources, including their emission rates and concentrations, and the technologies that can oxidize those emissions.

A high efficiency gas phase photoreactor for eradication of methane from low-concentration sources

“…Abernathy et al [17] found that light-based reactors must have a quantum yield for methane removal of at least 9 ± 8%, in order for the economic benefit of removing methane to exceed the energy cost. Given the demonstrated performance of MEPS with an AQY of 0.83% and anticipated improvements, the possibility that MEPS will meet the target set by Abernathy et al cannot be excluded.…”

“…A recent paper by Abernethy et al [17] has assessed methane oxidation technologies using a concentration based framework. This paper estimates, for the first time, the amount of methane emitted at a given concentration, showing that around 3/4 of methane emissions occur at a concentration below 1000 ppm.…”

Atmospheric methane removal may reduce climate risks

“…the chemical or biological conversion to carbon dioxide and water). Because methane is 43 times more potent than carbon dioxide per molecule, this conversion substantially reduces warming [15]. Roughly 95% of the methane sink is due to highly reactive atmospheric radicals (mainly hydroxyl, with a minor contribution from chlorine), while ∼5% is due to soil methanotrophs (methaneconsuming microbes) [5].…”

“…To be cost-effective at atmospheric concentrations, however, substantial breakthroughs are needed. For heat-based reactors, the operating temperature likely must be reduced from the current low of 300 • C down to below 30 • C [15]. For light-based reactors, including those that use photocatalysts and photolysis-based radical generation, the quantum efficiency (the ratio of oxidized methane molecules to incident photons) will need to be increased-from the current high of 0.8% potentially to at least 9% [15,19].…”

“…For heat-based reactors, the operating temperature likely must be reduced from the current low of 300 • C down to below 30 • C [15]. For light-based reactors, including those that use photocatalysts and photolysis-based radical generation, the quantum efficiency (the ratio of oxidized methane molecules to incident photons) will need to be increased-from the current high of 0.8% potentially to at least 9% [15,19]. For bioreactors, substantial technological breakthroughs are required to lower the lowest concentration at which they can operate from ∼500 ppm down to 1.9 ppm [20].…”