Conventional and Biological Direct Glycerol Fuel Cells: Review on Main Experimental and Model-Based Achievements

There is a growing body of research on the use of liquid fuels in fuel cells, including glycerol. The direct oxidation of glycerol in an abiotic (traditional, conventional) fuel cell can not only be used to produce electrical energy, but also to obtain high value-added products. Furthermore, recent experimental studies have employed glycerol in biological fuel cells, which could contribute to transforming the biodiesel industry. Bacterial cultures have been used to degrade glycerol to produce electricity, while enzymatic processes have also employed glycerol to produce electricity and products of interest. This way, the main aim of this review is to survey the principal factors influencing the use of conventional and biological (enzymatic and microbial) fuel cells. A summary of the reports found in the literature is provided concerning the selectivity towards adsorbed intermediates and products generated during the oxidation of glycerol in conventional fuel cells. Not only experimental but also model-based aspects are addressed. For biological fuel cells, an overview of the enzymes and microorganisms used is presented, in addition to addressing the specific electron transfer mechanisms and other relevant aspects (such as challenges and limiting parameters for function and performance).