In principle carbon capture using regenerative agriculture, ocean seeding/phytoplankton growth, biochar and algae production, coupled with societal relocalisation could become carbon negative to the tune of – 3 Gt of carbon per year, and yield a similar amount of useful biomass.

However, if phytoplankton could be caused to bloom, 1 Gt (billion tonnes) of carbon could be captured annually. It is claimed that regenerative agriculture might sequester around 3 Gt of carbon each year , and that by 2050, biochar production could account for another 1 Gt of carbon annually. In principle the carbon in the soil can stay there and improve its quality, but if the other kinds of captured carbon could be harvested, it might provide a useful potential source of biomass/fuel. Growing algae on a local pond could provide energy to replace fossil fuels for local communities, without impacting on arable land.

Since we emit 7 Gt/year of carbon from fossil fuels, the sum comes out something like (in Gt): 7 – 3 – 1 -1 = 2 Gt left to worry about. A cut in fossil fuel use by 50% through biomass curbs that to 1 Gt. Photosynthesis already absorbs around 3 Gt of carbon/year into oceanic phytoplankton and land-based plants, and if localised algal production cuts emissions from oil by another 1 Gt (assuming that we need 1 Gt less since we have that from algal biomass), the combined scheme is carbon negative by -3 Gt/year.

Hence in 40 years this would have cut 120 Gt of carbon from the atmosphere, which would reduce the concentration of CO2 by around 50 – 60 ppm.