Microbial Electrochemical Technologies for Biofuels and Bioenergy Production

Wastewater treatment and energy production are key points to grant the next generations health, economic, and environmental sustainability. The water–energy nexus represents a synergy between water, energy and the environment, leading to complex relationships between stakeholders, authorities, resources and environmental management. Research nowadays is focusing on developing efficient, green technologies based on water responsible use, sustainable energy management and environmental preservation; on the other hand, green energy production processes and resource recovery from waste streams are essential factors in environmental sustainability. Microbial electrochemistry is a branch of bioelectrochemistry based on the study and application of the interactions between living microbial cells and a solid-state electrode, serving well the purpose of the water-energy nexus. In the last two decades many biologist and microbiologists, chemists, biotechnologists, engineers have focused their interest on the different applications and interaction mechanisms of this new research field. Microbial Electrochemical Technologies (METs) present attractive applications, such as: (i) wastewater treatment, (ii) groundwater pollutants removal, (iii) water desalination and (iv) synthesis of added value carbon chemicals. In this context, two applications are thereby studied and operated in the present thesis, to investigate potential energy recovery options from waste streams: Microbial Fuel Cells (MFCs) and Microbial Electrosynthesis (MES). MFCs rely on direct conversion of the chemical energy of a substrate into electrical energy, while MES technology focus on electron (energy) utilization for chemical commodities production (for example, biofuels) using a liquid or gaseous waste stream as feedstock. However, the implementation of METs in scaled-up applications depends upon the optimization of microbial, technological, and economic issues: (i) use of genetically engineered bacteria, (ii) biological or chemical catalysts, (iii) materials, reactors and electrode design. Other strategies rely on integration of METs with different technologies. The present thesis also explores the possibility of combining microalgae and METs, and the possible products that can be recovered from waste streams in the attempt to improve the water-energy nexus balance.