for utilization by using HCO3 -pumps and maintaining an alkaline cytosolic pH. With these strategies, cyanobacteria accumulate high levels of intracellular HCO3 -, which can be converted to CO2 by CA to replenish substrate depletion in the carboxysome. Together, the nanoconfinement of RuBisCO, enzymatic acceleration of CO2 hydration kinetics, and accumulation of high HCO3 -levels enable cyanobacteria to efficiently concentrate and utilize atmospheric CO2 within carboxysomes. Similar to its role in cyanobacterial carbon fixation, HCO3 -offers an energy efficient method for CO2 concentration, which has been exploited for carbon capture in KOH solutions and has led to the development of bicarbonate and carbonate driven electrolyzers. These HCO3 -based carbon capture technologies avoid the energy penalties of CO2 desorption and separation by directly producing products from HCO3 -. CO2 capture as HCO3 -is a conceptually simpler approach than CO2 capture in amine solutions as carbamates where the CO2 can be released or reduced directly to form products , although this suffers from significant drawbacks in terms of energy efficiency and selectivity.