In the Carbon Engineering system, a remodeled industrial cooling tower containing a liquid hydroxide solution captures CO₂ and converts it into carbonate. The carbonate is then converted into pellets in equipment originally created to extract minerals in water-treatment plants. Finally, the carbon pellets are heated in a kiln originally designed for roasting gold, and transformed into pure carbon dioxide gas, which can be turned into synthetic fuel.

Keith’s team worked directly with commercial suppliers of each piece of repurposed equipment to design tests, engineer alterations, and develop cost estimates to adapt the hardware for a commercial direct-air-capture plant.

“In a post-Paris Accords world, everyone has been talking about carbon removal but most of the analysis is secondary literature or policy perspectives,” said Keith. “This is the first paper to estimate the cost of direct air capture based on a detailed engineering design and cost analysis. While uncertainties, of course, remain, the fact that it can be built using established processes and suppliers gives us confidence to develop industrial-scale plants.”

With that cost breakdown, direct air capture — especially direct air capture that can be used to make synthetic fuel — may look less exotic and more attractive to investors and policymakers.

In addition, the technology is location-independent, which should add to its allure, said Joe Lassiter, retired Senior Fellow and Senator John Heinz Professor of Management Practice in Environmental Management at the Harvard Business School.

“A commercial carbon capture facility could be located anywhere in the world where renewable or nuclear is inexpensive,” said Lassiter. “This is an example of how engineering and human cleverness can find economically feasible and sustainable solutions to the problems that society faces.”

To date, Keith and the Carbon Engineering team have raised about $30 million. The next step is to raise funds for a plant that can deliver fuels to market, which depends on finding a renewable power supplier who wants to supply high-capacity power at a low price and incentives for low-carbon fuels.

“I hope this paper will launch 1,000 master’s students to figure out how to create an even better future using this technology,” said Friedmann.