Two stage bioethanol refining with multi litre stacked microbial fuel cell and microbial electrolysis cell

•Ethanol was produced in a triple stack 10-L microbial fuel cell.•With lower loads currents and potentials oscillated in a self-synchronized manner.•Electrolysis conditions increased glucose conversion and ethanol productivity.•Fermentation waste was methanized in a 33-L microbial electrolysis cell stack.

Ethanol, electricity, hydrogen and methane were produced in a two stage bioethanol refinery setup based on a 10 L microbial fuel cell (MFC) and a 33 L microbial electrolysis cell (MEC). The MFC was a triple stack for ethanol and electricity co-generation. The stack configuration produced more ethanol with faster glucose consumption the higher the stack potential. Under electrolytic conditions ethanol productivity outperformed standard conditions and reached 96.3% of the theoretically best case. At lower external loads currents and working potentials oscillated in a self-synchronized manner over all three MFC units in the stack. In the second refining stage, fermentation waste was converted into methane, using the scale up MEC stack. The bioelectric methanisation reached 91% efficiency at room temperature with an applied voltage of 1.5 V using nickel cathodes. The two stage bioethanol refining process employing bioelectrochemical reactors produces more energy vectors than is possible with today's ethanol distilleries.

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