Considering durability in carbon dioxide removal strategies for climate change mitigation

This Perspective describes the various dimensions of Carbon Dioxide Removal (CDR) durability and interprets them in the context of current policy making. Durability - together with scalability and sustainability - is an essential condition of CDR. It depends on (i) the duration of CO2 storage and (ii) the risk of reversing such storage. The risk profile of durability varies widely across CDR methods. Because engineered, novel CDR methods involve more stable forms of CO2 storage than nature-based CDR, these methods are often promoted as a priority for CDR mitigation investments. However, shorter-term CDR plays an essential role in balancing sources and sinks of greenhouse gases in the second half of this century. Decision makers must also consider CDR policies in a larger context that takes into account readiness and feasibility, policy alignment and co-benefits of different CDR methods. They must also address durability in CDR policies and contracts, which tend to span much shorter timeframes than those contemplated by science when discussing durability. We argue that nature-based conventional CDR and novel engineered CDR that show complementary timing and risk profiles can be deployed in synergistic CDR portfoliosto balance the conditions of durability, feasibility and social and environmental sustainability.