Published in the journal One Earth, carbon scientists from Heriot-Watt University in Edinburgh, UK, and the University of Pennsylvania, Philadephia, US, have outlined a new way of projecting the cost of direct air capture (DAC) – and it could cost much more than the $100/t originally estimated.

Dr Mijndert Van der Spek, Heriot-Watt University, notes: ‘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 $100–600/t of CO₂ 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.’

He continues: ‘It’s a little unclear why the rate of $100/t 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.’

According to the research, the new price tag doesn’t make the technology unviable, as Van der Spek says: ‘There is no 1.5°C 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.’

Instead of estimating the cost of DAC using common costing methods for existing technologies, the research teams used a new approach specifically for technologies that are not commercial yet.

The 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, according to the research.  

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, according to the report.

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 DAC. ‘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 US has launched regional DAC hubs, applications for which are currently under review.’

Van Der Spek suggests that the UK could consider contracts for difference (CfD) to create a market and potentially lower the cost of financing DAC 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 US 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,’ he notes.

Heriot-Watt’s Research Centre for Carbon Solutions says it is now investigating the performance and costs of different materials for DAC, and feeding this into fully-fledged environmental and energy systems models. It is hoped this will lead to more granularity on the technology and a better understanding of how DAC can be integrated into the wider economy.

New US carbon capture pilot project
In other news, Calpine has unveiled a carbon capture demonstration project at Pittsburg’s Los Medanos Energy Center, California, US. The pilot project will use a chemical solvent developed by ION Clean Energy to bind with CO₂ in the plant’s flue gas.

The process is expected to capture as much as 95% of the carbon emitted at the 678 MW plant. It will capture about 10 t/d of CO₂ for approximately 13 to 18 months under the 1 MW test, the company says.

The $25mn project is being funded mainly by a Department of Energy-National Energy Technology Laboratory grant while ION and Calpine will share the remaining 20% of the costs.