Constraints on the Efficiency of Engineered Electromicrobial Production

• Published in: Joule Vol. 4; no. 10; pp. 2101 - 2130
• Main Authors: Salimijazi, Farshid, Kim, Jaehwan, Schmitz, Alexa M., Grenville, Richard, Bocarsly, Andrew, Barstow, Buz
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 14.10.2020; Elsevier
• Subjects: biofuels; carbon dioxide fixation; electricity storage; electromicrobial production; microbial electrosynthesis; synthetic biology; systems biology; systems biology; synthetic biology; microbial electrosynthesis; electricity storage; electromicrobial production; biofuels; carbon dioxide fixation
• ISSN: 2542-4351; 2542-4351
• DOI: 10.1016/j.joule.2020.08.010

Electromicrobial production aims to combine electricity and microbial metabolism for solar and electrical energy storage. We have constructed molecule to reactor models of highly engineered electromicrobial production systems that use H2 oxidation and direct electron transfer (DET). We predict electrical-to-biofuel conversion efficiency could rise to 52% with engineered in vivo CO2 fixation. H2 diffusion at ambient pressure requires areas 20 to 2,000 times the solar photovoltaic (PV) area supplying the system. Agitation can reduce this below the PV area, and the power needed is negligible when storing ≥1.1 megawatts. DET systems can be built with areas ≤ 15 times the PV area and have low energy losses even with natural conductive biofilms and can be even smaller if the conductivity could be raised to match conductive artificial polymers. Schemes that use electrochemical CO2 reduction could achieve efficiencies of almost 50% with no complications of O2 sensitivity. [Display omitted] •Predicts EMP electricity to biofuel conversion efficiency•Re-engineering in vivo CO2 fixation can increase efficiency to ≈52%•EMP powered by H2 oxidation is most efficient in ≥ 1 megawatt systems•EMP efficiency using electrochemically fixed CO2 could exceed 50% with no O2 sensitivity The penetration of renewable electricity is increasing significantly making low-cost, large-scale energy storage essential. At the same time, the need for CO2 sequestration and hydrocarbon fuels are likely to grow for decades to come. Photosynthesis gives a template for solar energy and CO2 storage at enormous scale, but its inefficiency sets the stage for land competition. We have developed a theory that lets us calculate the efficiency of microbes that absorb electricity and store CO2 as biofuels with greater efficiency than photosynthesis. We outline 10 development scenarios including re-engineering direct electron uptake microbes with high-efficiency CO2 fixation; scaling up H2-oxidizing microbe systems to store megawatts of electricity; engineering direct electron uptake microbes to make highly conductive artificial biofilms to enable high power density electricity storage; and engineering microbes that assimilate electrochemically reduced CO2 with electron uptake. We have developed a theory that lets us calculate the efficiency of microbes that absorb electricity and store CO2 as biofuels with greater efficiency than photosynthesis. We outline 10 development scenarios including re-engineering direct electron uptake microbes with high-efficiency CO2 fixation; scaling up H2-oxidizing microbe systems to store megawatts of electricity; engineering direct electron uptake microbes to make highly conductive artificial biofilms to enable high power density electricity storage; and engineering microbes that assimilate electrochemically reduced CO2 with electron uptake.