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The longer we wait to take serious action on climate change, the more necessary it becomes to remove some of the CO₂ we’ve already put in the air. In fact, the scenarios in the most recent Intergovernmental Panel on Climate Change report in which warming was limited to 2°C relied heavily on CO₂ removal.

Adoption of the necessary technology still seems too far off, given the current lack of market incentives and supporting policies. The technique seen as most likely to scale up involves growing biofuel crops and burning them in power plants that capture the CO₂ so it can be injected into underground storage. Like any scheme, this has drawbacks—it could compete with food crops for farmland, for example.

A new study led by the University of California, Santa Cruz’s Greg Rau highlights another tool for our CO₂ removal toolbox: splitting seawater to produce hydrogen gas for fuel while capturing CO₂ with ocean chemistry.