Microbial fuel cells in electricity generation with waste treatment:Alternative electron acceptors

Microbial fuel cell (MFC) have attracted great interest in recent years as a technology thatuses microorganisms to oxidize organic and inorganic materials at the anode for the purposeof bioelectricity generation and bioremediation. In MFC systems, energy can be obtained byusing all kinds of organic matter as substrate, from simple molecules (acetate, carbohydrates,glucose etc.) to complex compounds (molasses, cellulose, wastewater, waste sludge, domesticagricultural and animal wastes etc.). In addition to wastewater treatment, MFC technologyhas additional benefits such as sulfate removal, heavy metal removal, denitrification and nitrification. However, the low power efficiencies and potential losses of these systems limit theirapplicability on a real scale. Although the anode chamber of MFC systems has been studiedin detail over many different parameters, the cathodic electron acceptors have been studiedrelatively less. In MFC systems, electron acceptors are one of the main parameters influencingpower generation as they contribute to overcoming potential losses at the cathode. Oxygen hasa relatively high redox potential and is the traditional electron acceptor used in MFC systemsas it is reduced to form a clean product like water. However, the need for alternative electronacceptors has increased due to the fact that feeding oxygen to the cathode chamber requiresadditional energy and the need for catalysts due to the slow O2 reduction rate. Electricity generation by reducing certain electron acceptors at the cathode chamber has promising potentialfor bioenergy production, and the use of pollutants such as nitrogen species, heavy metalsand perchlorate as electron acceptors reduces the cost for their specific treatment. This reviewaims to summarize the various electron acceptors used in MFC systems, compare their effectson MFC performance, and discuss possible future areas.