What’s the best way to lock up carbon emissions—and make money doing it?

Fuels, cement, and plastics are just a few products that can be made with carbon dioxide. But not all these products are made equal when it comes to climate benefits. A study published in Nature scrutinizes various pathways to use carbon dioxide to assess which ones give valuable products while helping mitigate climate change by locking away the greenhouse gas.

The international team of researchers behind the study weighed the costs, benefits and climate-fighting potential of ten different pathways or technologies to capture and utilize carbon dioxide. The CO₂ could be captured from burning fossil fuels, directly from the atmosphere, or biologically sequestered.

The ten pathways include CO₂-based chemical products like polymers; CO₂-based fuels; microalgae fuels and products; concrete; CO₂-enhanced oil recovery; bioenergy with carbon capture and storage (BECCS); mineralization of atmospheric CO₂; reforestation or sustainable forestry; soil carbon sequestration techniques; and biochar.

Just because a pathway utilizes CO₂ that does not mean all that CO₂ is being stored or removed so it isn’t necessarily combating climate change, the researchers caution. Fuels and microalgae, for instance, have nearly no removal potential because when they are used, the greenhouse gas ends up back in the atmosphere. Concrete and wood, on the other hand, can sequester CO₂ for the long term. The five land-based biological pathways offer the biggest long-term opportunity to remove and store carbon dioxide.

On average, each pathway could store or remove around 0.5 gigatonnes of CO₂ per year, the authors found. And they suggest that a price on carbon emissions of less than $100 a tonne would incentivize over 1.5 gigatonnes of carbon capture.

There is no silver bullet, of course. Each pathway faces its own technological, policy and economic challenge. “Greenhouse gas removal is essential to achieve net zero carbon emissions and stabilize the climate,” said Cameron Hepburn, professor of environmental economics at the University of Oxford. “The promise of CO₂ utilization is that it could act as an incentive for CO₂ removal and could reduce emissions by displacing fossil fuels. Policymakers need to think like investors and fund a portfolio of options.”

Source: Cameron Hepburn et al. The technological and economic prospects for CO₂ utilization and removal. Nature, 2019.