Microbially catalyzed bioelectrochemical power devices come of age

Microbial extracellular electron transfer-based processes are rapidly progressing toward real-world wastewater treatment applications, but their technological progress as an electric power source remains elusive. It is mainly due to low and unstable density high internal resistance of the bioelectrochemical systems. In a recent Energy & Environmental Science article, Bombelli coworkers report bio-photovoltaic energy harvester system using photosynthetic microorganisms at Al anode that can widely used microprocessor Arm Cortex M0+ for 6 months without supporting devices. The idea microbially driven devices production has long been under investigation with varying degrees success. After concept was postulated in 1911 by M.C. Potter1Potter Electrical effects accompanying decomposition organic compounds.Proc. R. Soc. Ser. B. 1912; 84: 260-276Google Scholar later investigated briefly 1960s National Aeronautics Space Administration explore use such manned spacecrafts waste treatment, accompanied generation,2Scott, W. R., G. H. Rohrback M. Del Duca, 1962 Biochemical Fuel Cell Potentialities Flight, American Rocket Society Power Systems Conference, September 25-28, 1962.Google research picked up pace from year 2000. first 15 years, focus still on understanding concept,3Kim H.J. Park H.S. Hyun M.S. Chang I.S. Kim B.H. A mediator-less microbial fuel cell metal reducing bacterium, Shewanella putrefaciens.Enzym. Microb. Technol. 2002; 30: 145-152https://doi.org/10.1016/s0141-0229(01)00478-1Crossref Scopus (0) Google conducting proof-of-concept studies,4Kim J.R. Min Logan B.E. Evaluation procedures acclimate electricity production.Appl. Microbiol. Biotechnol. 2005; 68: 23-30https://doi.org/10.1007/s00253-004-1845-6Crossref PubMed (424) setting standard methodology5Logan Hamelers Rozendal Schröder U. Keller J. Freguia S. et al.Microbial cells: methodology technology.Environ. Sci. 2006; 40: 5181-5192https://doi.org/10.1021/es0605016Crossref (4897) basic transfer mechanisms, exploring variety wastes wastewaters substrates cells (MFCs).6Pandey P. Shinde V.N. Deopurkar R.L. Kale S.P. Patil S.A. Pant D. Recent advances different simultaneous recovery.Appl. Energy. 2016; 168: 706-723https://doi.org/10.1016/j.apenergy.2016.01.056Crossref (558) However, most these initial studies were short-duration ones executed small reactors. Even when long-term performance assessed, it materials perspective identify durability stability reactor components electrodes membranes or separators. Only years efforts have made upscaling systems, reactors reaching sizes 800 L7Jadhav D.A. Das I. Ghangrekar M.M. Moving towards practical applications sanitation resource recovery.J. Water Proc. Eng. 2020; 38: 101566https://doi.org/10.1016/j.jwpe.2020.101566Crossref (82) 1,500 L8Rossi Hur A.Y. Page M.A. Thomas A.O. Butkiewicz J.J. Jones D.W. Baek Saikaly P.E. Cropek D.M. Pilot scale air cathodes producing while treating wastewater.Water Res. 2022; 215: 118208https://doi.org/10.1016/j.watres.2022.118208Crossref (37) being reported. other approach upscale MFCs miniaturization stacking.9Ledezma Stinchcombe A. Greenman Ieropoulos self-sustainable stack.Phys. Chem. Phys. 2013; 15: 2278https://doi.org/10.1039/c2cp44548dCrossref (72) readily usable version systems al.10Bombelli Savanth Scarampi Rowden S.J.L. Green D.H. Erbe Årstøl E. Jevremovic Hohmann-Marriott M.F. Trasatti al.Powering photosynthesis.Energy Environ. 2529-2536https://doi.org/10.1039/d2ee00233gCrossref (23) time (BPV) aluminum M0+, microprocessor. About size AA battery, this device reported work over months. BPV be considered hybrid technology integrates photovoltaics MFC technologies. compartment contains alga named Synechocystis generates electrons harvesting sunlight. These (or current) interact transferred open-air cathode through external circuit. Aluminum one abundant metals Earth’s crust, available large quantities classified non-toxic. Hence, authors justified its inexpensive electrode system. testing lab environment dark-light conditions confirming current photo-active component, i.e., microorganisms, compact unit (Figure 1A) tested powering Cortex-M0+ domestic within temperature range 13.8°C 30.7°C. processor drew average 1.4 ± 0.4 μA voltage 0.72 0.14 V 1B). accomplished 1.23 × 1011 cycles 45 min computation followed 15-min standby period. investigators also larger prototype 2 years. Al-BPV attributed electrochemical oxidation activity 1C). Though mixed, dynamic scenario proposed involved, continuous output photo-response time, even covered passivating oxidized components, suggested dominance mode electrical mature Since operated non-sterile environment, anodic inhabited complex microbiome consisting both photoautotrophic heterotrophic groups end experiments. original pure culture turned into mixed key heterotrophs include Halomonas Pseudomonas genera, known harbor electroactive bacteria. microbes processes—through direct contact indirectly via redox mediators—to link (fixed photoautotrophs) reduction insoluble acceptor, electrode, achieve respiration. Such syntrophic community may offer enhanced less susceptibility contamination get affected changes occur extended periods operation. This brings envisioned application step closer implementation, especially microprocessors electronic appliances requiring (in few μW mW). As claim, trillions predicted Internet Things (IoT) Li-ion batteries would indeed impractical considering limited Li reservoirs. Additionally, charge discharge cycles. attractive alternative commonly expanding IoT applications. remarkable seems robust adjustable. outstanding challenges remain addressed achieving higher efficiencies finding low-cost scalable besides behavior performance-determining anode, air-cathode, functions. Further demonstrations actual field sites, particularly remote locations where conventional sources unavailable, need conducted assess commercial applicability. So far, bioelectric biosensors. Nevertheless, reporting ambient light sole input any additional battery fuel, study paves way developing implementing photosynthetically powered broader scale. For happen, policymakers industry should take seriously invest resources develop applicable technology. declare no competing interests.