Sustainable scale-up of negative emissions technologies and practices: where to focus


 Most climate change mitigation scenarios restricting global warming to 1.5 oC rely heavily on Negative Emissions Technologies and Practices (NETPs). Here we updated previous literature reviews and conducted an analysis to identify the most appealing NETPs. We evaluated 36 NETPs configurations considering their technical maturity, economic feasibility, greenhouse gas removal potential, resource use, and environmental impacts. We found multiple trade-offs among these indicators, which suggests that a regionalised portfolio of NETPs exploiting their complementary strengths is the way forward. Although no single NETP is superior to the others in terms of all the indicators simultaneously, we identified 16 Pareto-efficient NETPs. Among them, six are deemed particularly promising: forestation, Soil Carbon Sequestration (SCS), enhanced weathering with olivine and three modalities of Direct Air Carbon Capture and Storage (DACCS). While the co-benefits, lower costs and higher maturity levels of forestation and SCS can propel their rapid deployment, these NETPs require continuous monitoring to reduce unintended side-effects – most notably the release of the stored carbon. Enhanced weathering also shows an overall good performance and substantial co-benefits, but its risks – especially those concerning human health – should be further investigated prior to deployment. DACCS presents significantly fewer side-effects, mainly its substantial energy demand; early investments in this NETP could reduce costs and accelerate its scale-up. Our insights can help guide future research and plan for the sustainable scale-up of NETPs, which we must set into motion within this decade.