Why Capturing Methane Is So Difficult
Avoiding the worst impacts of climate change may require removing methane from industrial emissions streams and the atmosphere — but researchers are so far stymied on how to capture the potent planet-warming gas.
Methane lasts in the atmosphere only a decade or two, compared with carbon dioxide’s centuries. But it traps 80 times as much heat, helping drive near-term warming and potentially kick-starting a feedback loop that would release even more gas from natural sources.
A technology that removed methane from the air could significantly change the rate of global warming in the relatively near future, said Desirée Plata, a professor of civil and environmental engineering at the Massachusetts Institute of Technology.
Most people think it’s going to go away on its own, but the problem with that thinking is that methane will do the same amount of damage as CO.2 Over the next decade, even though it’s less abundant in the atmosphere,” Plata said in an interview.
Federal policymakers have largely focused on the need for carbon capture to limit global warming to below 2 degrees Celsius, alongside reducing fossil fuel emissions. Incentives in the Inflation Reduction Act have further encouraged a boom in planned projects to remove carbon dioxide from both the air and industrial emissions.
The field of methane removal lags far behind. Companies can prevent methane emissions from occurring or use anaerobic “digesters” to cut down on the gas in organic waste — but researchers are still grappling with how to remove methane once emitted.
Meanwhile, global oil and gas projects continue to leak around 70 megatons of methane each year, or the equivalent of burning almost 2 million pounds of coal.
Soon, US facilities will pay for every metric ton of methane they release, after the Inflation Reduction Act put a price on methane emissions for the first time.
The trouble with methane
Methane is emitted from oil and gas projects, livestock, and even landfills as waste breaks down.
But as the planet warms, methane may also escape from natural sources. A 2021 study Researchers from Stanford University found that historical greenhouse gas emissions have already set in motion natural feedback loops that could cause massive methane releases from permafrost and other sources.
Methane removal, researchers concluded, “may be needed to offset continued methane release and limit the global warming contribution of this potent greenhouse gas.”
But methane is 200 times less abundant in the atmosphere than CO2 — a scarcity that makes removing it a technical challenge.
Capturing methane would require processing a lot of air, which could require an unfeasibly large amount of energy. It is also more resistant than CO2 to conversion into a solid or liquid form, said Jack Leonard, director of the Reducing Emissions of Methane Every Day of the Year program at the Energy Department’s Advanced Research Projects Agency-Energy.
“CO2 you can capture from the air or you can capture from flue gas because it has a chemical structure that allows you to kind of put a ‘hook’ on it, but the methane molecule does not — and so capturing methane is very, very difficult, Leonard said in an interview.
Most methane removal technologies thus focus on oxidizing the greenhouse gas rather than “hooking” it out of the air, Leonard said.
Porous minerals called zeolites, for example, trap methane in their microscopic pores, oxidize the gas and release it as CO2.
Zeolites’ potential was overlooked for decades because they don’t efficiently convert methane into chemicals that have obvious commercial applications, such as methanol, said Plata, the MIT professor.
But the minerals are efficient at converting methane to CO2, which downgrades the gas’s global warming impact, Plata said. That CO2 could also be converted into ethanol, she said, which has an established market.
Plata leads a team that is working on incorporating small pellets of zeolite minerals into a reaction chamber that could be deployed by both the fossil fuel and agriculture sectors. The device could work particularly well in coal mines, where methane concentrations are relatively high, Plata said.
Other researchers are developing methane capture technologies that harness the metabolisms of living organisms.
Some bacteria produce enzymes that oxidize methane, trapping the greenhouse gas and causing it to undergo a chemical reaction. Researchers hope to build bioreactors that could house those bacteria, oxidizing methane near emission sources.
Thomas Wood, a professor of chemical engineering at Pennsylvania State University’s College of Engineering, said in an interview that such a bioreactor could capture methane at energy production points, including hydraulic fracturing sites.
Some fracking sites currently trap methane before it enters the atmosphere and transport it to refineries, where it is converted to methanol, a liquid alcohol that can be used to make a variety of industrial chemicals. But that solution has drawn criticism from environmental groups, as huge volumes of methane can be released during transport.
A bacterial bioreactor would cut out the risk and expense of transporting captured methane from fracking or other emissions sites, because it would turn the greenhouse gas into useful chemicals on the spot, Wood said.
Wood’s research team has previously demonstrated that its engineered bacteria can convert methane into acetate, an industrial chemical, and polylactate, which can be used to manufacture biodegradable polymers.
The outlook for oil and gas
The oil and gas industry is one of the largest sources of methane emissions, making it a potential customer for successful methane capture.
But methane oxidation technologies will need to achieve industry scale before they can be deployed effectively, said Samantha Ruelas, a materials scientist at Lawrence Livermore National Laboratory. Ruelas works on a research team that is building bacterial bioreactors for methane oxidation.
“We would need to really be sure that our technology can match what their production needs are,” Ruelas said in an interview, referring to oil and gas companies. “So if they’re producing too much methane and our cells can’t keep up with them, that could potentially be an issue.”
Better methane-sensing technologies would also help make methane-destroying bioreactors effective solutions for oil and gas companies, Ruelas said.
The technology works best when it is fed a stream of gas with a relatively high methane concentration. Ideally, facilities would be able to pinpoint a specific emissions source — like a pipeline leak — and “attach” a reactor at that site, she said.
That method of deployment would also make sense economically, said Sam Abernethy, an author of the Stanford study who is an applied physics doctorate candidate at the university and research assistant at its Doerr School of Sustainability.
The cost to oxidize methane is driven in large part by the concentration of methane in the air, he said. Oil and gas production sites have higher concentrations of methane that may be particularly suited to oxidation technologies.
Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2023. E&E News provides essential news for energy and environment professionals.
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