Capturing carbon from the air could cost six times more than hoped, according to a new report from Heriot-Watt published in the journal One Earth.
Direct air capture technology removes carbon dioxide from the air and either stores or puts the carbon to use.
It’s a relatively new technology - globally there is just one commercial-scale plant in operation in Iceland. Two more are under construction - one in Iceland and one in Texas.
Dr Mijndert Van der Spek and colleagues from Heriot-Watt's Research Centre for Carbon Solutions compiled the new report with colleagues from the University of Pennsylvania, Philadelphia.
The carbon scientists have developed a new way of projecting the cost of direct air capture.
Van der Spek says the higher-than-expected cost can be mitigated, if governments invest now.
Van der Spek said: “The US government’s Carbon Negative Shot is working towards a cost of 100USD per tonne of carbon dioxide removed, as are other organisations like the market maker Frontier Climate Fund.
“Our model, based on scenarios of four different direct air capture technologies in seven different countries, shows that the future cost is likely to range from 100-600USD per tonne of carbon dioxide removed from the atmosphere.
“That’s if we reach deployment of a gigatonne of carbon removal every year - anything below that and the cost will be higher.
“It’s a little unclear why the rate of 100USD per tonne was adopted; it seems some earlier scientific studies, as well as some direct air capture entrepreneurs, have pushed this or even lower values into the public domain.
Van der Spek says the new price tag doesn’t make the technology unviable.
“There is no 1.5 degree scenario that doesn’t involve removing carbon from the atmosphere. We can cut our greenhouse gas emissions to zero and we’ll still need to deal with the carbon that’s already there.
“The best way to get direct air capture technologies down the cost curve and make a planet-wide impact is for governments to invest now in direct air capture technology to deploy it at scale more quickly.
“That’s the only way to bring down the cost. We can act now or pay even more later.”
Calculating the cost of direct air capture
Instead of estimating the cost of direct air capture using common costing methods for existing technologies, Van der Spek and his colleagues used a new approach specifically for technologies that are not commercial yet.
Their method accounts for the costs rising at first when scaling the technology from the lab to the first commercial plant, and then slowly going down due to large-scale production.
Other studies had overlooked or disregarded the rising costs incurred until the first commercial deployment, leading to low-cost estimates.
The Heriot-Watt team also included the performance and capital costs of using solid absorbents, which are used by the commercial-scale plant in Iceland, which previous projections haven’t.
It’s the same as what has been observed with wind turbines and solar panels. They also use ranges for each model input, and only present ranges as outputs, rather than point estimates.
Catered policy support for direct air capture
Van Der Spek points out that governments have historically invested in new technologies to advance them quickly and create a market.
He says the same is now required for direct air capture.
“This technology is of global importance; it really can’t be overstated.
“Wind energy and solar energy received governments’ subsidies to get them off the ground and look at how successful that has been in countries like the UK.
“The UK government launched the direct air capture and other greenhouse gas removal technologies competition, which is a good starting point, and the USA has launched regional DAC hubs, applications for which are currently under review.
“The UK could consider Contracts for Difference to create a market and potentially lower the cost of financing direct air capture projects, or provide grants or state loans. These have been used successfully for renewable technologies like onshore and offshore wind.
“Tesla benefitted greatly from cheap state loans in the USA in its early years.
“Different countries will have different mechanisms available to them, the policy is up for them to decide. But they must do it quickly.”
Van der Spek and the team at Heriot-Watt’s Research Centre for Carbon Solutions are now investigating the performance and costs of different materials for direct air capture, and feeding this into fully-fledged environmental and energy systems models. This will lead to more granularity on the technology and a better understanding of how direct air capture can be integrated into the wider economy.