Most schemes to capture and reuse carbon actually increase emissions

Alex Wilkins

Most carbon capture and utilisation technologies emit more carbon than they capture. This finding suggests that CCU projects, which have attracted billions of dollars in investment, won't do much to achieve the Paris Agreement's emissions targets.

Carbon dioxide can be taken out of the atmosphere either directly from the air or from pollution sources, and can be put to use in processes such as making fuel, plastics and concrete. CCU doesn't store the CO2 for long periods. CCU technologies use energy to convert CO2 into fuels or CO2 itself to drive other industrial processes.

The life cycles of more than 40 CCU processes were assessed against three criteria: could they permanently store CO2, does the CO2 they collect come from atmospheric and natural sources, and does the process have zero emissions.

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The majority of the technologies failed to meet these criteria, with 32 emitting more carbon than they captured. Four of the methods appeared to be ready for use. CO2 can be used in oil and concrete production.

If you're stuck with a technology that doesn't have the potential to really reduce emissions, then that could be a situation that's undesirable.

Stuart Haszeldine at the University of Edinburgh in the UK says that engaging in some of these activities actually uses more carbon.

Many of the technologies don't seem ready for deployment on a large scale, so they may not be helpful in hitting the Paris Agreement's emission targets.

The analysis used assumptions about future electricity mix that could change, for example, electricity was assumed to be completely renewable by 2050, which could make CCU even more carbon intensive.

De Kleijn hopes the research will help policy-makers and investors decide which technologies are worth investing in.

The use of carbon capture technologies is promoted by the Global CCS Institute. There are some positive things to say about CCU, but the point that the researchers are making is that not all CCU technologies are the same.

It would be better to focus on trying to store carbon for thousands of years.

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