Strategies to reduce emissions of carbon dioxide (CO2) from fossil fuels, and hence mitigate climate change, include energy savings, development of renewable biofuels, and carbon capture and storage (CCS). For CCS, several scenarios are being considered. One approach is capture of point-source CO2 from power plants or other industrial sources and subsequent injection of the concentrated CO2 underground or into the ocean. An alternative to this point-source CCS method is expansion of biological carbon sequestration of atmospheric CO2 by measures such as reforestation, changes in land use practices, increased carbon allocation to underground biomass, production of biochar, and enhanced biomineralization. In addition to geological or oceanic CO2 injection, novel models for point-source CCS based on accelerated weathering and biomineralization are emerging, utilizing either abiotic or biotic processes. Biomineralization of CO2 by calcium carbonate (CaCO3) precipitation is a common phenomenon in marine, freshwater, and terrestrial ecosystems and is a fundamental process in the global carbon cycle.
Employment of cyanobacteria in biomineralization of carbon dioxide by calcium carbonate precipitation offers novel and self-sustaining strategies for point-source carbon capture and sequestration. Although details of this process remain to be elucidated, a carbon-concentrating mechanism, and chemical reactions in exopolysaccharide or proteinaceous surface layers are assumed to be of crucial importance. Cyanobacteria can utilize solar energy through photosynthesis to convert carbon dioxide to recalcitrant calcium carbonate. Calcium can be derived from sources such as gypsum or industrial brine. A better understanding of the biochemical and genetic mechanisms that carry out and regulate cynaobacterial biomineralization should put us in a position where we can further optimize these steps by exploiting the powerful techniques of genetic engineering, directed evolution, and biomimetics.