Electricity generation and microbial community changes in microbial fuel cells packed with different anodic materials Yanmei Sun, Jincheng Wei, Peng Liang, Xia Huang ⇑ State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, PR China article info Article history: Received 10 July 2011 Received in revised form 9 September 2011 Accepted 10 September 2011 Available online xxxx Keywords: Microbial fuel cell Anodic material Electricity generation Microbial community abstract Four materials, carbon felt cube (CFC), granular graphite (GG), granular activated carbon (GAC) and gran- ular semicoke (GS) were tested as packed anodic materials to seek a potentially practical material for microbial fuel cells (MFCs). The microbial community and its correlation with the electricity generation performance of MFCs were explored. The maximum power density was found in GAC, followed by CFC, GG and GS. In GAC and CFC packed MFCs, Geobacter was the dominating genus, while Azospira was the most populous group in GG. Results further indicated that GAC was the most favorable for Geobacter adherence and growth, and the maximum power densities had positive correlation with the total bio- mass and the relative abundance of Geobacter, but without apparent correlation with the microbial diver- sity. Due to the low content of Geobacter in GS, power generated in this system may be attributed to other microorganisms such as Synergistes, Bacteroidetes and Castellaniella. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction In recent years, a general trend towards sustainability and increased efficiency capturing the energy present in wastewater streams drove scientists and researchers to explore more econom- ically and environmentally friendly technologies. Microbial fuel cells (MFCs), which utilize microorganisms as the catalyst to promote the biodegradation of organic materials and generate power simultaneously, have drawn great attention (Bond et al., 2002) on this front. MFCs have the potential to purify wastewater (Luo et al., 2010; Patil et al., 2009), desalinate sea water (Cao et al., 2009a; Chen et al., 2011), produce hydrogen (Wagner et al., 2009) and hydrogen peroxide (Fu et al., 2010), serve as biosensors (Cao et al., 2009b), etc. Although MFCs have been thoroughly investi- gated, their technology is still under extensive laboratory research. Main challenges for their practical application are their high costs and low power generation capability once they are scaled up. Anodic materials play a major role in the performance and cap- ital cost of MFCs. Commonly used materials include: carbon paper, carbon felt, graphite (in the form of rods, particles, fiber, brush etc.), with usually prohibitive prices. Studies show that the cost of anode materials accounts for about 10% of the total cost of MFCs (Rozendal et al., 2008). Different anode materials differ in conduc- tivity, surface area and porosity. These differences tend to affect the adhesion and growth of electrochemically active bacteria. Therefore identifying highly effective and biocompatible anode materials is urgently needed to accelerate the practical application of MFCs. Generally, the power generation capacity is in fact believed to be closely related to the biofilm formed on the anodes as microbes adhere to its surface (Rabaey and Rozendal, 2010). Therefore a bet- ter understanding of the ecological behavior of microbial commu- nities in different conditions will be helpful for the improvement of MFCs design and operation. Reports show that the microbial com- munity changes with factors including the substrate type (Kan et al., 2011; Zhang et al., 2011), external resistance (Jung and Regan, 2010; Rismani-Yazdi et al., 2011), open/closed circuit condi- tions (de Carcer et al., 2010; Larrosa-Guerrero et al., 2010), and type of MFCs (Kiely et al., 2011). It was found that the variation of operating conditions had potential impacts on the diversity and composition of microbial communities, two factors which are believed to further influence the MFCs performance. The phys- ico-chemical characteristics of different electrode materials have an important impact on microbial colonization. However, few re- ports have been found to address the composition of microbial communities involved in anodic electrode materials of packed bed microbial fuel cell. Larrosa-Guerrero et al. (2010) analyzed the microbial diversity variance among different carbon electrode materials using the denaturing gradient gel electrophoresis (DGGE). However, microbes dominating in different carbon elec- trode materials were not specified. The present study aims to seek low-cost, highly effective and biocompatible anodic materials as well as better understand the microbial community involved in electricity generation. Two types of inexpensive materials, granular activated carbon (GAC) and 0960-8524/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.biortech.2011.09.038 ⇑ Corresponding author. Tel.: +86 10 62772324; fax: +86 10 62771472. E-mail address: xhuang@tsinghua.edu.cn (X. Huang). Bioresource Technology xxx (2011) xxx–xxx Contents lists available at SciVerse ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech Please cite this article in press as: Sun, Y., et al. Electricity generation and microbial community changes in microbial fuel cells packed with different anodic materials. Bioresour. Technol. (2011), doi:10.1016/j.biortech.2011.09.038