The use of microbial fuel cells to generate electrical current is increasingly being seen as a viable source of renewable energy production In this Progress article, Bruce Logan highlights recent advances in our understanding of the mechanisms used by exoelectrogenic bacteria to generate electrical current and the important factors to consider in microbial fuel cell design There has been an increase in recent years in the number of reports of microorganisms that can generate electrical current in microbial fuel cells Although many new strains have been identified, few strains individually produce power densities as high as strains from mixed communities Enriched anodic biofilms have generated power densities as high as 69 W per m2 (projected anode area), and therefore are approaching theoretical limits To understand bacterial versatility in mechanisms used for current generation, this Progress article explores the underlying reasons for exocellular electron transfer, including cellular respiration and possible cell–cell communication

Exoelectrogenic bacteria that power microbial fuel cells

Waste biomass is a cheap and relatively abundant source of electrons for microbes capable of producing electrical current outside the cell. Rapidly developing microbial electrochemical technologies, such as microbial fuel cells, are part of a diverse platform of future sustainable energy and chemical production technologies. We review the key advances that will enable the use of exoelectrogenic microorganisms to generate biofuels, hydrogen gas, methane, and other valuable inorganic and organic chemicals. Moreover, we examine the key challenges for implementing these systems and compare them to similar renewable energy technologies. Although commercial development is already underway in several different applications, ranging from wastewater treatment to industrial chemical production, further research is needed regarding efficiency, scalability, system lifetimes, and reliability.

http://science.sciencemag.org/content/sci/337/6095/686.full.pdf

Conversion of wastes into bioelectricity and chemicals by using microbial electrochemical technologies.

Water has always been crucial to combustion and hydroelectric processes, but it could become the source of power in membrane-based systems that capture energy from natural and waste waters. Two processes are emerging as sustainable methods for capturing energy from sea water: pressure-retarded osmosis and reverse electrodialysis. These processes can also capture energy from waste heat by generating artificial salinity gradients using synthetic solutions, such as thermolytic salts. A further source of energy comes from organic matter in waste waters, which can be harnessed using microbial fuel-cell technology, allowing both wastewater treatment and power production.

Membrane-based processes for sustainable power generation using water

Microbial fuel cells: From fundamentals to applications. A review

https://www.cell.com/trends/biotechnology/pdf/S0167-7799(08)00159-5.pdf

Towards practical implementation of bioelectrochemical wastewater treatment.

Enhanced Coulombic efficiency and power density of air-cathode microbial fuel cells with an improved cell configuration

Hydrogen production using single-chamber membrane-free microbial electrolysis cells

Phosphate buffer solution has been commonly used in MFC studies to maintain a suitable pH for electricity-generating bacteria and/or to increase the solution conductivity. However, addition of a high concentration of phosphate buffer in MFCs could be expensive, especially for wastewater treatment. In this study, the performances of MFCs with cloth electrode assemblies (CEA) were evaluated using bicarbonate buffer solutions. A maximum power density of 1550 W/m3 (2770 mW/m2) was obtained at a current density of 0.99 mA/cm2 using a pH 9 bicarbonate buffer solution. Such a power density was 38.6% higher than that using a pH 7 phosphate buffer at the same concentration of 0.2 M. Based on the quantitative comparison of free proton transfer rates, diffusion rates of pH buffer species, and the current generated, a facilitated proton transfer mechanism was proposed for MFCs in the presence of the pH buffers. The excellent performance of MFCs using bicarbonate as pH buffer and proton carrier indicates that bicarbon...

Sustainable Power Generation in Microbial Fuel Cells Using Bicarbonate Buffer and Proton Transfer Mechanisms

Hydrogen production in single-chamber tubular microbial electrolysis cells using non-precious-metal catalysts

Hydrogen production by microbial electrolysis cells (MECs) provides a completely new avenue for the production of hydrogen from biomass. The key competitive advantage of this technology compared with previous techniques for biohydrogen generation is that the biomass can be utilized fully for H2 conversion. This review provides a brief overview of recent advances in research on electrochemically active bacteria, electrode materials, MEC design and performance and fuel sources of MECs. Enhancing the hydrogen-production rate and lowering the energy input are the main challenges of MEC technology. The review concludes that breakthroughs in the development of efficient cathode material, scalable MEC design and cost-efficient pretreatment processes are needed for future studies.

Hongqiang Hu

Papers

Enhanced Coulombic efficiency and power density of air-cathode microbial fuel cells with an improved cell configuration

Hydrogen production using single-chamber membrane-free microbial electrolysis cells

Sustainable Power Generation in Microbial Fuel Cells Using Bicarbonate Buffer and Proton Transfer Mechanisms

Hydrogen production in single-chamber tubular microbial electrolysis cells using non-precious-metal catalysts

Microbial electrolysis: novel technology for hydrogen production from biomass.