Biological CO₂ Utilization; Current Status, Challenges, and Future Directions for Photosynthetic and Non-photosynthetic Route

The anthropogenic emission of greenhouse gases (GHGs), especially CO₂, is becoming an economic and societal challenge globally. CO₂ utilization in a closed loop is an essential approach for reducing its greenhouse effects and regulating environmental pollution in a cost- and energy-effective way. On this frontier, chemicals and fuels can be produced from CO₂ as a potential strategy for reducing its emissions. One of the promising and environmentally friendly carbon capture and utilization (CCU) approaches is a biologically mediated method. Numerous microorganisms, such as bacteria, algae, and fungi, have demonstrated the ability to convert CO₂ into a wide range of valuable compounds through various metabolic pathways. These biological processes have shown great potential in achieving high CO₂ conversion efficiencies and generating economically viable products such as bio-alcohols with conversion efficiencies ranging from 50 to 90%. In addition to their high CO₂ conversion efficiencies, biological CO₂ utilization methods also offer advantages in terms of cost-effectiveness. Compared to traditional methods of CCU, biological approaches are generally more economically feasible due to their ability to utilize CO₂ from the atmosphere or flue gas streams, eliminating the need for expensive capture and purification processes. Despite its many advantages, this approach faces a few challenges, such as low fixation rate, lower biomass density, and scale-up. This review details the photosynthetic and non-photosynthetic CO₂ fixation methods, followed by a brief comparison of these two methods and the thermocatalysis process of CO₂ conversion. Also, research progress has been discussed in improving the efficiency and economics of biological CCU processes, such as synthetic biology. Finally, recent developments, challenges, and prospects for future research regarding biological CO₂ conversions were discussed.