Anode process: microbial oxidation of substrate

Thursday, 26 March 2009

To date, many organic substrates have been investigated as possible energy sources to generate electricity using MFCs. Below, an overview is given of the substrates which have been used to fuel MFCs.

The substrates used in MFCs range from carbohydrates (glucose, sucrose, cellulose, starch), volatile fatty acids (formate, acetate, butyrate), alcohols (ethanol, methanol), amino acids, proteins and even inorganic components such as sulfides or acid mine drainages (Cheng et al., 2007, Clauwaert et al., 2008c, He et al., 2005, Heilmann and Logan, 2006, Ishii et al., 2008, Liu et al., 2005b, Logan et al., 2005, Min and Logan, 2004, Rabaey et al., 2003, Rabaey et al., 2006). In order to benchmark new MFC components, reactor designs or operational conditions, acetate is commonly used as a substrate because of its inertness towards alternative microbial conversions (fermentations and methanogensis) at room temperature. This results in high coulombic efficiencies of up to 98% (Rabaey et al., 2005b) and high power outputs of up to 115 W.m³(Cheng and Logan, 2007) for mixed anodophylic cultures.

Although the use of a pure or single substrate allows to study the metabolic processes and conversion products during the microbial conversion, it is not feasible to power full scale MFCs with pure substrates from an economical point of view. In that perspective, the use of second generation bio-fuels or organic waste streams is highly promising because it allows to combine the actual treatment of the waste stream with the generation of energy. A range of more complex organics, containing a large variety of different readily and non-readily degradable molecules such as domestic wastewater (Liu et al., 2004), brewery wastewater (Feng et al., 2008), paper recycling wastewater (Huang and Logan, 2008) or the effluent of anaerobic digesters (Aelterman et al., 2006a) have been demonstrated to generate electrical power in MFCs. Nevertheless, the power outputs using wastewater are about a factor 10 lower compared to pure substrates (Aelterman et al., 2006a, Clauwaert et al., 2008a). Moreover, the composition of the wastewater is strongly affecting the power output of MFCs. Rabaey et al., (2005b) found that spiking the wastewater with acetate resulted in an increase of the power output, indicating that the higher the rapidly biodegradable fraction within the wastewater is, the higher the power output will be.

The type of substrate fed to a MFC potentially has an impact on the structure and composition of the microbial community. The more reduced the substrate is, the more energy there is available to divide across the community. This may lead to an increase of the possible interactions and niches. Up till now, no clear image of the effect of the type of substrate on the microbial community is available.

Redrafte after:

Aelterman, P. (2009) Microbial fuel cells for the treatment of waste streams with energy recovery. PhD Thesis, Gent University, Belgium

References cited:

Aelterman, P., Rabaey, K., Clauwaert, P. & Verstraete, W. (2006). Microbial fuel cells for wastewater treatment. Water Sci Technol 54, 9-15.

Cheng, S., Dempsey, B. A. & Logan, B. E. (2007). Electricity generation from synthetic acid-mine drainage (AMD) water using fuel cell technologies. Environ Sci Technol 41, 8149-8153.

Cheng, S. & Logan, B. E. (2007). Ammonia treatment of carbon cloth anodes to enhance power generation of microbial fuel cells. Electrochem Commun 9, 492-296.

Clauwaert, P., Aelterman, P., Pham, H. T., De Schamphelaire, L., Carballa, M., Rabaey, K. & Verstraete, W. (2008a). Minimizing losses in bio-electrochemical systems: the road to applications. Appl Microbiol Biotechnol 79, 901.

Clauwaert, P., Van der Ha, D. & Verstraete, W. (2008b). Energy recovery from energy rich vegetable products with microbial fuel cells. Biotechnol Lett DOI 10.1007/s10529-008-9778-2.

Feng, Y., Wang, X., Logan, B. E. & Lee, H. (2008). Brewery wastewater treatment using air-cathode microbial fuel cells. Appl Microbiol Biotechnol 78, 873-880.

He, Z., Minteer, S. D. & Angenent, L. T. (2005). Electricity generation from artificial wastewater using an upflow microbial fuel cell. Environ Sci Technol 39, 5262-5267.

Heilmann, J. & Logan, B. E. (2006). Production of electricity from proteins using a microbial fuel cell. Water Environ Res 78, 531-537.

Huang, L. P. & Logan, B. E. (2008). Electricity generation and treatment of paper recycling wastewater using a microbial fuel cell. Appl Microbiol Biotechnol 80, 349-355.

Ishii, S., Shimoyama, T., Hotta, Y. & Watanabe, K. (2008). Characterization of a filamentous biofilm community established in a cellulose-fed microbial fuel cell. BMC Microbiol 8.

Liu, H., Ramnarayanan, R. & Logan, B. E. (2004). Production of electricity during wastewater treatment using a single chamber microbial fuel cell. Environ Sci Technol 38, 2281-2285.

Liu, H., Cheng, S. A. & Logan, B. E. (2005). Production of electricity from acetate or butyrate using a single-chamber microbial fuel cell. Environ Sci Technol 39, 658-662.

Logan, B. E., Murano, C., Scott, K., Gray, N. D. & Head, I. M. (2005). Electricity generation from cysteine in a microbial fuel cell. Water Res 39, 942-952.

Min, B. & Logan, B. E. (2004). Continuous electricity generation from domestic wastewater and organic substrates in a flat plate microbial fuel cell. Environ Sci Technol 38, 5809-5814.

Rabaey, K., Lissens, G., Siciliano, S. D. & Verstraete, W. (2003). A microbial fuel cell capable of converting glucose to electricity at high rate and efficiency. Biotechnol Lett 25, 1531-1535.

Rabaey, K., Clauwaert, P., Aelterman, P. & Verstraete, W. (2005). Tubular microbial fuel cells for effcient electricity generation. Environ Sci Technol 39, 8077-8082.

Rabaey, K., Van de Sompel, K., Maignien, L. & other authors (2006). Microbial fuel cells for sulfide removal. Environ Sci Technol 40, 5218-5224.