A new approach to carbon capture and storage that has been proposed by University of California Berkeley researchers requires two ingredients to cost-effectively sequester atmospheric carbon for durations of thousands of years: vegetation and salt.

The carbon-negative scheme is based on biomass crop cultivation to capture atmospheric carbon. Harvested vegetation is then buried in engineered dry bio-landfills along with salt to keep the material dry, suppress microbial activity and retard decomposition. Such agro-sequestration is proposed to enable stable storage of biomass carbon.

The researchers estimate that for every metric ton of dry biomass, about 2 tons of carbon dioxide can be sequestered. The approach promises cost-effectiveness in addition to long-term stability: the agriculture and biolandfill costs total $60/ton of captured and sequestered carbon dioxide, far lower than the $600/ton costs incurred by available direct air capture and carbon dioxide gas sequestration strategies.

Candidate crops for deployment with polyethylene water diffusion barrier geomembranes to prevent water ingress are identified in Proceedings of the National Academy of Sciences. This sequestration solution can scale without encroaching upon or competing with food-producing tracts, as many of the recommended biomass crops can be grown on marginal pasture and forest lands, or on fallow farmland.