Biomass composting with gaseous carbon dioxide capture

Abstract

Biomass carbon removal and storage (BiCRS) technologies must scale rapidly to mitigate climate change via the removal of carbon dioxide (CO2) from the atmosphere. BiCRS technologies passively concentrate atmospheric CO2 and thus greatly reduce energy demands for atmospheric carbon removal, relative to direct air capture (DAC) technologies. Composting with gaseous CO2 capture is an overlooked BiCRS technology with significant potential for atmospheric carbon removal. For the first time, we demonstrate the capture of high purity gaseous CO2 from biomass composting. Biomass is composted in simple, closed reactors with automated cycling of air or oxy-fuel to generate gaseous streams with CO2 concentrations varying between 18 and 95%, which are significantly higher than the CO2 concentration of air (∼0.04%); the minimum thermodynamic energy needed for CO2 capture from composting is 72–98% lower than that for the capture of CO2 directly from the air. Genomic data indicate microbial diversity decreases with the use of oxy-fuel relative to air. Globally, the composting of food waste could capture 0.3–1.0 billion tonnes of biogenic CO2 per year, and the inclusion of other biomass feedstocks could increase the total capture rate to more than 3.5 billion tonnes per year.