Turning industry food waste into power, improved treatment

In recent years, there has been growing interest in harnessing microorganisms for simultaneous wastewater treatment and renewable bioelectricity production. Microbial fuel cell (MFC) technology can convert the chemical energy stored in organic matter in wastewater into electricity, using bacteria as a catalyst. Researchers in Iran have been investigating how modification of the electrodes can improve the performance of this technology.

In this study, published in the SCI Journal of Chemical Technology and Biotechnology, researchers have developed a novel and cost-effective anode catalyst (TiO2-HX@MWCNT-COOH-Al2O3) that is designed to improve and stabilise the power generation performance of MFCs treating vegetable oil industry wastewater.

The choice of anode material is key to dictating the efficiency and cost-effectiveness of MFCs, as it is the site at which bacteria grow and form a biofilm.

Speaking to SCI, Dr Hossein Jafari Mansoorian, Hamadan University of Medical Sciences, Iran, said: “In order to improve bacterial adhesion and efficient electron transfer between bacteria and the electrode surface, the electrode should be modified and its surface area increased to ensure efficient current collection and power yield through the decomposition of organic compounds in the wastewater … Based on the results of this study, TiO2-HX@MWCNT-COOH-Al2O3 structure of this composite is a suitable candidate for modifying the anode electrode and greatly enhances electroactivity.”

The team also investigated modification of the cathode to identify a cost-effective alternative to platinum. Carbon felt modified with powdered activated carbon (PAC) originating from Bambuseae (a family of bamboo plants) was found to be effective.

The large volumes of wastewater generated by the vegetable oil industry mean that the high energy requirements of conventional wastewater treatment are unsustainable. Mansoorian noted, “since traditional wastewater treatment has various limitations, sustainable implementations of MFCs might be a feasible option in wastewater treatment as well as green electricity production, bio-hydrogen synthesis, carbon sequestration and environmentally sustainable sewage treatment”.

Asked about the scalability of MFCs, Mansoorian explained that “although some basic knowledge has been gained in MFC research, there is still a lot to be learned in the scale-up of MFC technology for large-scale applications”.

“For MFCs to be a viable option for wastewater treatment, they need to be scaled up to accommodate large volumes of incoming wastewater, which has proven challenging for several reasons, including minimising the distance between the anode and cathode to reduce electrical losses and being cost-competitive with other treatment technologies. 

“The materials used are expensive, including membranes to separate the electrodes, which are prone to fouling, and a catalyst to produce enough power. At last, after obtaining superior anode electrodes, it is necessary to examine their long-term performance in real wastewater treatment to investigate their stability, durability, mechanical properties and secondary pollution effects.”

Nonetheless, Mansoorian noted that “MFCs undoubtedly have potential in terms of energy recovery during wastewater treatment, occupying a market niche in terms of a standalone power source and also in the direct treatment of wastewater”.

Image credit: iStock.com/Roman Starchenko