Microbial fuel cells could be used to treat wastewater

Energies Journal recently published a paper in which researchers assessed global industrial wastewater production and investigated the use of microbial fuel cells (MFCs) for the treatment of wastewater as an independent technology enabling substantial global-scale energy savings.

Roughly 84% of all energy generated in the world is still derived from fossil fuels. Wastewater comprises significant quantities of thermal and chemical energies, which are currently undervalued in traditional wastewater treatment methods, such as anaerobic digestion (AD). However, its treatment requires energy-intensive methods. The chemical energy within wastewater is referred to as the chemical oxygen demand or COD, which represents the amount of oxygen required for the oxidation of the wastewater organic matter.  

“MFC technology allows direct energy generation in the form of an electric current from wastewater. This process can be a more environmentally sound substitute for AD. Unlike AD, which requires temperatures over 30 °C, MFCs function across wide COD loading and temperature ranges. Furthermore, stable power output can be achieved by AD in months, whereas MFCs require only a few days. However, MFC technology has laboratory-scale limitations due to its inability to provide adequate power density, which becomes a commercialization obstacle”.

As reported by the United Nations Educational, Scientific, and Cultural Organization (2017), the total annual water extraction was expected to be 3,928 km3, of which 24% came from industrial and municipal wastewater production. 

Since the power generated is low, on a scale of a few W/m3, MFCs are presently seen as a treatment method rather than a power generation system. Recent research, however, has indicated that power generation efficiency in MFCs has improved significantly over the years, approaching 1 kW/m3 in liter-scale reactors. Several studies on real and synthetic wastewater indicated that, unlike the AD process, MFC technology could be self-sufficient since the energy produced during the treatment fulfills the complete energy requirements for the system’s operation.

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The researchers found that MFC technology exhibited the potential for energy recovery from several wastewater types. Other key advantages of MFC-based wastewater treatments were also highlighted. 

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