Capturing carbon from biomass energy production or using huge banks of industrial fans to suck it out of the air—two technologies still in the research phase—may become part of the future of reducing climate pollution.
The two approaches have been identified to scrub the atmosphere of carbon dioxide and stabilize the climate.
Research from the World Resources Institute joins a growing chorus of scientists, climate action groups, and companies such as the Canadian firm Carbon Engineering that are calling for a worldwide effort to not only reduce carbon emissions but also remove fossil fuel pollution from the air to prevent climate change from spiraling out of control and meet Paris climate accord targets.
“We need emissions reductions and we need carbon removal,” research lead author James Mulligan, a WRI associate, told Bloomberg Environment. “We have to figure out how to do both.”
Direct Air Capture
Sucking carbon dioxide from the ambient air using groupings of industrial-sized fans that capture it on absorbent material before storing it underground is also likely to help achieve global climate goals. Much more research is needed, though, to determine how to cut costs and scale it up enough to make a dent in global warming, according to WRI.
Carbon Engineering, which is demonstrating a direct air capture plant in British Columbia, estimated in June that it could pull carbon from the air for between $94 and $232 per ton, down from previous estimates of $1,000 per ton. The company didn’t respond to requests for comment Sept. 12.
Direct air capture technology “must be cost-competitive with other carbon removal or emissions reductions measures in order to be deployed at a large scale,” the report said, adding that previous research shows that only the most stringent climate policies and carbon pricing will make direct air capture profitable, and only late this century.
It’s unclear how the cost questions surrounding direct air capture technology will be resolved because capturing carbon from the atmosphere and storing it underground on a widespread scale is difficult to make profitable, Mulligan said.
“The service it’s providing is a public good—just burying it underground,” he said. “Eventually, we need to be able to store this stuff at immense scale. It’s contingent upon whether society is willing to pay for that service.”
Trees and other plants such as switchgrass naturally remove carbon dioxide from the air and store it. Some researchers think that burning that kind of biomass for energy, then capturing and storing the carbon emissions, will reduce the carbon dioxide that has accumulated above the Earth.
Mulligan’s team concluded that bioenergy generation with carbon capture and storage could help scrub the atmosphere of carbon dioxide if questions about its costs and effectiveness can be answered.
The questions include what kind of trees and crops need to be grown, how and where captured carbon would be transported and stored, and what growing crops for carbon sequestration might mean for food production, the study says.
Cost estimates vary widely from $15 to $400 per ton of removed carbon dioxide, and more research needs to be done to keep those costs low.
Mulligan and his team are calling on the federal government to support carbon-removal technology research and development and create a market for carbon captured directly from the air to overcome each method’s costs and other limitations.
The technology to remove carbon hasn’t been proven to work at a large enough scale to stabilize the climate, and the costs are far from certain.
But momentum to answer those questions has picked up pace this year as major universities and nonprofit groups have announced new programs to develop negative emissions technology.
Those include the University of Michigan’s Global CO2 Initative and the Energy Futures Initiative, led by former Energy Secretary Ernest Moniz, which announced a carbon dioxide air-capture project in September aiming to help the federal government develop negative emissions technologies.
Carbon removal is also expected to become part of discussions about how countries can meet their Paris Agreement commitments when nations gather at international climate negotiations in December in Poland.
Decarbonizing Not Enough
Many scientists have long recognized that cutting fossil fuel emissions down to zero and fully decarbonizing the global economy won’t be enough to prevent climate change from becoming catastrophic.
The math behind the Paris Agreement doesn’t add up unless countries create “negative emissions"—drawing carbon dioxide emissions from burning fossil fuels down to zero and then removing about two decades’ worth of climate pollution from the atmosphere by the end of the century.
The agreement calls for capping global warming at 1.5 degrees Celsius above pre-industrial levels and preventing it from exceeding 2 degrees Celsius.
“1.5 degrees is completely unattainable unless you take CO2 out of the atmosphere,” Peter Wadhams, an ocean physicist at Cambridge University who studies sea ice and is unaffiliated with the WRI research, told Bloomberg Environment. “We need a massive international effort, massive government effort. We could do it. All it’s a matter of doing is finding the technology to bring the cost down.”
Carbon removal has been called a “moral hazard” by some scientists because they see it as distracting from the Paris agreement’s main goal of cutting carbon emission.
The WRI research takes the “emotional edge” off of carbon-removal discussions by showing that removing carbon is necessary to gain control of the climate, Klaus Lackner, director of the Center for Negative Carbon Emissions at Arizona State University, who is unaffiliated with the research, told Bloomberg Environment.
“The WRI report makes such ideas [carbon removal] more tractable because it takes away the notion that removing carbon is somehow not the right thing to do,” Lackner said. “In the end, CO2 is a waste management issue and we need to stop dumping it into the atmosphere.”
WRI will host a forum featuring Mulligan and Lackner Sept. 18 in Washington, on how carbon removal can be used as a solution to climate change.