Phototrophic microbial fuel cells for sustainable power generation and wastewater treatment

Microbial fuel cells (MFCs) rely on the capacity of electrode-adhered electroactive bacteria to oxidize organic matter and generate electrons. Typical MFCs are highly engineered systems that can be applied as green tools to alleviate the burden of waste streams. Phototrophic MFCs (PhMFCs) are a promising variant that can be implemented indoors or outdoors and use the power of the sun to boost efforts in on-site environmental remediation, biomass generation, and power generation. PhMFC variations include plant-based and algal-based MFCs. Algal-based MFCs can incorporate special photosynthetic action at either the anode or cathode, enhancing or replacing the role of other bacteria in regular bacterial MFCs. Plant-based MFCs can be more complex due to the role of the root system near an electrode and its interaction with electrode-adhered bacteria, and they are nearly universally operated outdoors in either natural or engineered conditions. This review considers PhMFCs such as algal-based MFCs, algal carbon capture cells (ACCCs) and anode algal microbial fuel cells (AAMFCs), and also plant-based MFCs which include natural plant MFCs (NPMFCs), constructed wetland MFCs (CWMFCs), and marine-rooted plant MFCs (MPMFCs). After summaries of the fabrication and function of different PhMFCs, we elaborate with a literature review and discussion on each variant, followed by suggestions for future directions that will enhance the impact and accelerate the uptake of these promising multi-functional biosystems.