This story was updated in December 2023 to reflect the subsequent commercialization of technologies described here.
Carbon dioxide (CO2) levels today are higher than at any point in the past 800,000 years or more.
During a year when terms like carbon neutrality and net zero have become more and more commonly used, it appears the world is waking up to the imperative underscored in every high-level climate assessment—humanity needs to make a drastic change to stem the most catastrophic climate change consequences.
Climate impacts are happening more quickly than many scientists had predicted. Greenhouse gases are making the planet hotter. That rise in temperature is disrupting the weather and climate system in profound and cascading ways.
In its 2020 report, The UN Environmental Programme (UNEP) concluded that despite a slight dip in atmospheric CO2 created by the pandemic lock down in 2019, “the world is still heading for a catastrophic temperature rise in excess of 3°C this century—far beyond the Paris Agreement goals of limiting global warming to well below 2°C and pursuing 1.5°C.” It goes on to say, to avoid the worst consequences of global warming, we need to remove 10 billion tons of CO2 from the air by 2050.
In other words, in addition to drastically cutting global fossil fuel emissions, society needs to develop and use technologies to remove the CO2 already in the atmosphere. This is a huge undertaking, but one that scientists at Lamont-Doherty Earth Observatory have been striving toward for more than a decade.
Decarbonization, the process of capturing CO2 from the air and from industrial processes, has been in various stages of development at Lamont-Doherty for several years. One of many strategies that researchers are developing involves harnessing a natural process by which the Earth itself takes back CO2 from the air.
Geologist Peter B. Kelemen is a research scientist at Lamont-Doherty Earth Observatory and the Arthur D. Storke Memorial Professor in the Department of Earth and Environmental Sciences. He has been a key architect of the Oman Drilling Project, an initiative involving more than 200 international scientists from disciplines such as geophysics, geochemistry, geology, biology, and physics who are working on research topics related to a unique geological feature in the Oman desert. In this region, the oceanic crust and its underlying mantle rocks have been thrust up onto the surface, creating the largest on-land exposure of ocean crust and upper mantle in the world.
Atmospheric CO2 spontaneously reacts with rocks from the Earth’s interior, the mantle, to form “carbonate” minerals, both removing CO2 from air, and permanently storing it in solid form. This is driven by the chemical energy due to disequilibrium between mantle rocks and the atmosphere.
Kelemen studies the chemical and physical processes of reaction between fluids and rocks. His primary focus now is on CO2 removal from air and permanent storage via engineered methods that emulate natural carbon mineralization. While his work in this area began in 2006, during fiscal year 2020, his discoveries have begun to fuel exciting industry investment and commercialization.
Kelemen and co-workers have developed several patents for processes that harness this naturally available chemical energy to yield low cost CO2 removal from air and geological storage.
“We wanted to figure out the cheapest way to take carbon dioxide out of the air and we came up with something very simple: Take limestone, cook it. Now you have CO2, to store or use, and calcium oxide. Put the CaO out in the weather. It will draw down CO2 from air, to make limestone again. Repeat. This is so simple, it is almost stupid. But we are finding that we can convert 75 percent of CaO to limestone in less than two weeks, just reacting with air in the lab. And, because the process is so simple, it currently has the lowest peer-reviewed cost estimate, of any proposed method for direct air capture.”
Two start-up companies are putting Kelemen’s innovation to work.
California-based Heirloom Carbon Technologies is committed to removing one billion tons of CO2 from the air by 2035 by “looping” CaO and CaCO3, as described above. Based on a process Kelemen and colleagues described in a 2020 paper, Heirloom opened its first plant in November 2023, the first commercial operation to remove carbon directly from the air. It can absorb up to 1,000 tons of carbon a year, a relatively small amount, but Heirloom hopes to expand quickly. To earn revenue, the company sells carbon removal credits to other companies looking to offset their own emissions; Microsoft has already signed a deal with Heirloom to remove 315,000 tons.
Meanwhile, 44.01, run by an entrepreneur in Oman, is focusing on storing CO2 removed from air by forming solid carbonate minerals in rocks below Oman’s surface, also based on techniques co-developed by Kelemen. The project got a big shot in the arm when then heir to the British throne Prince William (now King William) awarded it a $1.2 million Earthshot Prize. The prize is aimed at funding cutting-edge environmental research across the world. The company is now working to scale up a series of pilot projects into a commercial operation. Rocks similar to those in Oman are found in other parts of the world including Papua New Guinea and the U.S. West Coast.
“It’s very gratifying to finally see these things moving,” said Kelemen.