Practical and thermodynamic constraints on electromicrobially accelerated CO2 mineralization

By the end of the century, tens of gigatonnes of CO2 will need to be removed fromthe atmosphere every year tomaintain global temperatures. Naturalweathering of ultramafic rocks and subsequent mineralization reactions can convert CO2 into ultra-stable carbonates. Although this will draw down all excess CO2, itwill take thousands of years. CO2 mineralization could be accelerated byweathering ultramafic rocks with biodegradable lixiviants. We show that if these lixiviants come from cellulosic biomass, this demand could monopolize the world's biomass supply. We demonstrate that electromicrobial production technologies (EMP) that combine renewable electricity and microbial metabolism could produce lixiviants for as little as $200 to $400 per tonne at solar electricity prices achievable within the decade. We demonstrate that EMP could make enough lixiviants to sequester a tonne of CO2 for less than $100. This work highlights the potential of this approach and the need for extensive R&D.

Automated summary

By the end of the century, a large amount of CO2 needs to be removed annually to maintain global temperatures. Natural weathering of ultramafic rocks can convert CO2 into stable carbonates, but it takes thousands of years. Using biodegradable lixiviants from cellulosic biomass can accelerate CO2 mineralization, but it may deplete the world's biomass supply. Electromicrobial production technologies (EMP) that combine renewable electricity and microbial metabolism can produce affordable lixiviants and sequester CO2. This study highlights the potential and need for extensive R&D in this approach.