Carbon capture technology may be essential in helping the world in the fight against climate change. By fitting fossil fuel power stations and industrial emitters with carbon capture technology, it is possible to reduce their carbon dioxide emissions by over 90%. Until renewable energy is capable of providing the bulk of the world’s power needs, carbon capture may have to play a major role if the world is to meet the 2°C warming target outlined by the Paris Agreement. “Carbon Capture, Utilization, and Storage 2021-2040”, a new report by IDTechEx, explores the technical and industrial factors that will play a role in deciding whether carbon capture technology can live up to its potential as a key technology in the fight against climate change.

However, capturing CO₂ from point sources such as power stations and steel manufacturing plants may not be enough to avoid the worst impacts of climate change. Most scenarios outlined by the Intergovernmental Panel on Climate Change (IPCC) for keeping the world below 2°C of warming require the active removal of CO₂ from the atmosphere. Outside of bioenergy with carbon capture and storage (BECCS), which remains highly unproven, this is not possible with point source carbon capture.

A potential solution is direct air capture (DAC) technology, which uses carbon capture techniques to strip CO₂ from atmospheric air. The technology has generated much excitement around the world, with many hoping it could help to directly reverse the impacts of climate change. However, despite the enthusiasm, the technology is still at a very early stage, is unproven at scale, and is currently far more expensive than point-source carbon capture. So, does DAC justify the excitement or is it doomed to fail? And why not just plant trees instead?

The DAC process is similar to an artificial tree; ambient air enters the DAC device and a range of chemical and physical processes extract the CO₂ before the rest of the air is released back into the atmosphere. However, the process is much more efficient than planting trees, requiring less land and fewer resources. For example, Swiss DAC company Climeworks claims that its plant in Hinwil, Switzerland, can remove 900 tonnes of CO₂ per year, the equivalent of 36,000 trees.

Commercial DAC methods work via a similar mechanism to point-source carbon capture. First, large fans push ambient air through a filter containing a substance that physically or chemically binds the CO­₂, with the CO₂-free air being released back into the environment. For example, sodium hydroxide solution will react with CO₂ to form a stable sodium carbonate precipitate. This carbonate can then be heated to produce a high purity gaseous CO₂ stream, which also enables the regeneration of the sodium hydroxide.