Performance of Metal Foams as MFC Electrodes and Characterization of Waste Streams from Pulp and Paper plants in Bioelectrochemical Systems

Conference poster, 2012

Optimization of electrode structure and materials is a subject taken into high consideration to improve the performance of microbial fuel cell (MFC) systems. In this work we show the use of novel electrodes made of metal alloys with a peculiar foam structure. The foam structure of the electrodes, realized according to a proprietary process, is intended to increase the electrode surface available to the microorganisms for the formation of the biofilm. Cast iron (GS800) and stainless steel (304) foams have been used as electrodes in MFC systems run with pure culture of Shewanella oneidensis. In general, foam electrodes showed better performance compared to the massive ones, in terms of current density at the anode. Metal foams with different porosities (i.e. 10, 20 and 30 pores per inch) were compared, showing that the pore density is a critical feature, clearly influencing the overall MFC output and the kinetics of the voltage generation throughout the run. These differences were potentially related to differences in the mass transfer and in the dynamics of the anode colonization by S. oneidensis, which were both affected by the varying porosities. Furthermore, MFC with stainless steel electrodes performed better than the ones using cast iron electrodes, most probably due to changes occurring on the cast iron surface affected by oxidation and corrosion phenomena. Concomitantly to MFC experiments aiming to test metal foam electrodes, we performed a study on the possible use of waste streams from a Swedish pulp and paper plant, exploiting the endogenous microbial populations present in the stream. Analysis of the chemical composition of the waste stream and of the microbial populations thriving in this environment was performed and followed by the analysis of dynamic changes occurring within a bioelectrochemical system. This exploratory study on the use of waste streams from pulp and paper plants aimed to set the basis for a future integration of bioelectrochemical systems into a wider biorefinery concept.