When I finally find the courage to tell my young daughter about the climate crisis I am half-expecting to hear this innocent rejoinder: "If we have spewed all that carbon pollution into the air, can we not just suck it back out again?"
It is not a silly question. "Direct air capture" (DAC) — an industrial process that removes carbon dioxide from ambient air so it can be locked away underground (or recycled into products like synthetic fuels) — sounds like science fiction. However, the technology to vacuum clean the skies already exists; it just has not been fully industrialised yet. It is a climate insurance policy we should not ignore.
I am not talking here about traditional carbon capture and storage, which is the process of removing CO2 from a power plant or factory smokestack. A DAC plant filters ambient air, and hence it can be built anywhere there is a surplus of low-carbon energy to run it.
Integrating direct air capture with nuclear power is one option. Another is using geothermal power, which is what the largest DAC facility yet constructed does. Built by a Swiss company called Climeworks AG, the Iceland plant has dozens of fans that suck air into a collector where the CO2 binds to a filter. After applying heat, the gas is then dissolved in water and pumped underground, where it gradually turns into stone.
While impressive, the Climeworks' facility will capture just 4,000 tons of CO2 a year, an amount that HSBC analysts note is equivalent to the pollution caused by just a few hundred cars. And the cost to remove a ton of carbon is around 10 times the equivalent cost of polluting in Europe's carbon market.
"If we have spewed all that carbon pollution into the air, can we not just suck it back out again?"
It is a challenging task: Though CO2 concentrations are far too high, the gas makes up just 0.04 percent of the air we breathe. Hence a DAC plant has to process around 2 million cubic meters of air just to extract one ton of CO2. Depending on the process used, it can require a 300 MW power system to remove 1 million metric tons of carbon.
Carbon Engineering Ltd., a Canadian rival, is developing a 1 million tons a year plant in the U.S. Permian basin in partnership with Occidental Petroleum Corp., and another in northeast Scotland in conjunction with British firm Storegga. Storegga has attracted investment from M&G Plc, Macquarie Group Ltd., GIC (Singapore's sovereign wealth fund) and Mitsui & Co. Ltd.
Even these are still several orders of magnitude too small to make a real dent in global emissions: We release about 39 billion tons of CO2 yearly. However, by starting small, the industry thinks it will learn how to construct much larger plants at a lower cost. There is no physical reason why "[we] will not be able to take a ton of CO2 out of the air for around $100 in the next ten to 20 years," Jan Wurzbacher, co-chief executive of Climeworks, told a DAC conference in September.
Subsidies and grants helped solar, wind power and electric vehicle manufacturers to innovate and scale up, and they can do the same for DAC. To attract more institutional investors, verifiable carbon removals need to be integrated into emissions trading systems, so more corporate and institutional investors are willing to pay for them.
There has been some progress on all these fronts. The bipartisan US infrastructure bill includes $3.5 billion for four DAC hubs, while the US budget reconciliation package includes higher tax credits for carbon capture. The UK has committed 100 million pounds ($138 million) for DAC research and it is considering how to include greenhouse gas removals in its emissions-trading system.
Microsoft Corp. founder Bill Gates and Tesla Inc.'s Elon Musk do not agree on much but both are writing large checks to support carbon removal. United Airlines Holdings Inc. Swiss Re AG, Stripe Inc. and Shopify Inc. are among companies paying to sequester carbon this way, as is the band Coldplay for its next world tour.
Some environmentalists fear carbon removal will distract from the important task of eradicating fossil fuel use; they note there are many other cheaper methods to lower emissions. They are wary that several oil companies are investing in the technology, and at least one wants to use captured CO2 to extract yet more oil.
DAC is not a silver bullet. Think of it as a "safety valve" or "backstop" that complements the other important actions we must take, Julio Friedmann, a senior research scholar at Columbia University's Center on Global Energy Policy says in this podcast.
Even if the energy transition is swift and successful, there will be some sectors, like airlines, where emissions will be difficult to fully eradicate, in part because they cannot be captured at the source. We will need to remove billions of tons of carbon yearly to reach climate neutrality and DAC can help reverse the damage we have done to the climate already. DAC is a more permanent and less land-intensive solution than simply planting a lot of trees, though of course, we should do that too.
So when my daughter asks if we can suck carbon out of the air, I will answer: Yes, we can. With the caveat there is still a lot of work to do, it will cost a lot and we do not have much time.
Chris Bryant is a Bloomberg Opinion columnist covering industrial companies. He previously worked for the Financial Times.
Disclaimer: This article first appeared on Bloomberg, and is published by special syndication arrangement.