Scientists agree that to avoid the worst impacts of climate change caused by humans emitting greenhouse gases (GHG), we must dramatically reduce the amount of carbon in the atmosphere. Such efforts are currently focused on reducing future emissions through energy efficiency, shifting to low carbon fuels, and/or by carbon capture and storage from power plants and factory smokestacks.
But to really avoid dramatic climate impacts, we may also need to reduce the carbon already emitted as well as offset future emissions that can’t practically be avoided. Current efforts on this front include planting trees and preserving existing forests since trees absorb carbon from the atmosphere. An alternative approach is to utilize a machine that can suck carbon out of the air. This is called Direct Air Capture (DAC), an industrial process that removes carbon from the air and allows it to be stored in permanent underground storage or to be used in making synthetic fuels. Here’s how this works:
While details vary from project to project, the overall concept is the same. Atmospheric air is sucked into the DAC unit with large fans. The air is circulated through either liquid chemical solutions that absorb carbon or through solid sorbent filters that chemically bind with carbon. Then a process is applied to remove the carbon from the liquid or the filters and combine it with oxygen, resulting in CO2. The CO2 can then be collected and used for other industrial processes, or it more likely will be sequestered in permanent underground storage.
The International Energy Agency (IEA) reports there are currently 19 DAC projects (capturing more than 0.01 Mt CO2/year) in the world. But all are small, mostly research or demonstration projects. The first commercial project in operation is the Orca plant built by Climeworks in Iceland. Climeworks uses the liquid method. (See a video on how it works here). Much of the company’s investment comes from corporations who are using Climework’s services to help achieve corporate low-carbon goals including Microsoft, Audi, Shopify, and Stripe.
Another company, Carbon Engineering, is currently engineering two larger DAC projects, one in west Texas and one in Scotland (their technology uses solid filters; learn about how it works from this video). Their investors include BHP, Chevron, Oxy Low Carbon Ventures, and the Bill Gates Foundation.
While DAC has been proven technologically, the biggest question is whether it can be made cost-effective. Climework’s current costs are believed to be in the range of $600 to $800/ton. But the current value of carbon reduction in today’s largest carbon trading markets is around $80/ton in Europe and $28/ton in California. Forecasts for future cost reductions, as DAC projects scale up and the technology is refined, suggest costs may be reduced to $200 to $300/ton in the next decade and ultimately to as low as $100/ton. This may be within the range of cost-competitiveness.
Some environmentalists are lukewarm on DAC because the concept doesn’t discourage carbon emissions but rather leads to a “ clean it up later” mentality. Others believe it may be an important tool to combat climate change. The U.S. government has included $3.5 billion for four DAC hubs in the recently passed infrastructure bill; other governments around the world are also supporting development; and Elon Musk has offered a $100 million X-prize for carbon removal.