Communications of the ACM
Capturing Carbon
Carbon capture is appealing because it could reverse the impact of atmospheric heating.
Credit: greenrecruitmentcompany.com
As violent storms, killer heat waves, and vicious wildfires have emerged as the new normal, mitigating climate change has become urgent. Of course, part of the solution is to reduce carbon dioxide (CO2) emissions and reach carbon-neutral status. Yet, this does nothing to decrease greenhouse gasses already trapped in the atmosphere.
"There is a considerable lag between carbon emissions and temperatures," says Phil De Luna, chief carbon scientist and head of engineering at Deep Sky, a Montreal, Canada company that focuses on building out carbon removal infrastructure at scale. "This is significant because unless we find a way to reduce output and lower existing atmospheric greenhouse gas levels, climate change will accelerate."
The answer may lie in pulling carbon dioxide out of the atmosphere.
Although the first carbon capture methods surfaced nearly a century ago, advances in the technology are rapidly reshaping the field. These include systems that pluck CO2 directly from air, and others that extract it from ocean water. At that point, it also is possible to change CO2 into mineralized rocks that can be sequestered underground.
"These technologies could have an enormous impact on minimizing the damage and destruction that would come with significantly higher global temperatures," says David Heldebrant, laboratory fellow for the Advanced Energy Systems Group at Pacific Northwest National Laboratory in Portland, OR.
Into Thin Air
The urgency of the situation cannot be ignored. Getting to carbon-neutral status will take decades, even as humans continue to pump 35 billion tons of carbon into the atmosphere every year. The result is a planet edging perilously close to heating beyond the 1.5 degrees Celsius (2.7 degrees Fahrenheit) threshold the Paris Agreement deems critical for avoiding catastrophic climate outcomes.
Carbon capture is appealing because it could reverse the impact of atmospheric heating. According to the International Energy Association (IEA), global carbon capture capacity is projected to increase nearly 700% from 2022 to 2030. IEA reports 338 projects with a total capacity of approximately 300 MtCO2/year are coming online in 2023. In the U.S., the Biden administration has announced a $1.2-billion investment in separate carbon-capture projects in Texas and Louisiana. Each hub aims to remove 250 times more carbon dioxide from the atmosphere than any existing facility.
Although collecting emissions at the machine or smokestack level is not new, researchers are pushing the technology far beyond conventional boundaries. For example, at the Pacific Northwest National Laboratory, Heldebrant and a team of scientists have developed a closet-sized prototype machine that would convert CO2 into single-use and recyclable materials at a projected 19% lower cost point than existing systems. The system grabs the output of a flue from power plants, uses a patented solvent to extract the CO2, and then converts the resulting material into substances like methanol.
Other carbon capture systems are blowing in a different direction. For instance, direct air capture technology sucks in huge volumes of ordinary air, extracts the CO2, then transforms it into a liquid. At that point, it can serve as a fuel or be mineralized and sequestered deep beneath the earth, where it cannot leak out. Not surprisingly, the efficiency and scalability of these systems is improving, while costs are dropping. Meanwhile, new ideas are appearing, including carbon capture via moving trains and other vehicles.
Carbon capture at sea is also making waves. For example, a joint project operated by public-private research organization AltaSea and carbon extraction firm Equatic is testing a 100-foot floating barge that pulls carbon dioxide directly from water. The electrochemical process—invented by researchers at the UCLA Institute for Carbon Management—stabilizes CO2 as dissolved bicarbonate ions that adopt the form of solid mineral carbonates. The technology also produces hydrogen, which can be used a green fuel.
Another startup, Captura, has developed a direct ocean capture system powered by renewable sea energy that works like a desalinization plant, removing carbon dioxide at a cost of about $100 per ton and sequestering it in underwater storage sites. The company uses a proprietary membrane system and electrodialysis to grab CO2.
Capturing carbon addresses only half of the problem, however; there's also a need to sequester it so it cannot leak back into the atmosphere. For instance, the company 44.01, named for the molecular mass of carbon dioxide, has developed a technology that turns CO2 into rock. 44.01 injects CO2 dissolved in water into peridotite formations deep underground, where temperatures and pressures accelerate naturally occurring mineralization. "In nature the process can take decades. We speed this up, so that it takes less than a year," says Karan Khimji, co-founder and chief commercial officer for 44.01.
Weathering Change
Despite enormous progress, carbon capture continues to face headwinds. For one thing, it is costly, and financial incentives are often lacking. For another, unless it plugs into renewable energy, net carbon reduction is minimal.
Scalability is also an issue. As Khimji puts it: "There are a lot of exciting carbon removal technologies that have demonstrated efficacy in pilots or small demonstrations but scaling them up is vital to removing gigatons of CO2 from the atmosphere every year—and avoiding the worst effects of climate change."
Indeed, questions remain about economics, the viability of emerging systems, and how and where CO2 deposits can be stored. Some carbon capture systems also require huge volumes of water and power to operate. A United Nations panel has gone so far as to describe many emerging methods as "unproven" and carrying "unknown" risks. Instead, it favors approaches revolving around greenhouse gas reduction.
Nevertheless, Deep Sky's De Luna believes the economics and practical foundation for carbon capture will fall into place—particularly as businesses strive to meet ambitious carbon reduction targets, including becoming net zero. He points out that technical knowledge is advancing rapidly, there's greater understanding of how to use different carbon reduction systems effectively than ever before, and Environmental, social, and corporate governance (ESG) and regulatory frameworks are falling into place. "It is becoming possible to connect all the dots," he says.
Carbon capture and sequestration tools may determine the fate of humanity. "We are at a crossroads," De Luna says. "We are going to have to find ways to pull carbon from the atmosphere—while continuing to reduce the amount of carbon humans generate. We need to conduct scientific research, but also find ways to commercialize and incentivize carbon capture."
Samuel Greengard is an author and journalist based in West Linn, OR, USA.
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