Biocement from the ocean: Hybrid microbial-electrochemical mineralization of CO.

Increasing concentrations of atmospheric CO are leading to rising global temperatures and extreme weather events. However, the most prominent method of removing CO via direct air capture remains cost-prohibitive. Oceans sequester carbon through several naturally occurring carbon dioxide removal (CDR) processes, one of which includes microorganisms that utilize dissolved inorganic carbon (DIC) in their metabolic processes. Atmospheric CO is in dynamic equilibrium with DIC at the ocean's surface. Thus, ocean-based CDR can function to capture carbon from the air indirectly. This work discusses a hybrid method that combines primary CO capture via the growth of autotrophic microorganisms (i.e., photosynthetic cyanobacteria) and microbially induced carbonate precipitation. Carbon fixation and carbonate precipitation can be co-optimized using bipolar membrane electrodialysis (BPMED) devices , which generate seawater with an adjustable pH. We examine the scale-up potential for naturally produced bio-carbonate composite material and compare its production with published ocean CDR strategies for reducing anthropogenic CO emissions.