A compact, membrane-less, easy-to-use soil microbial fuel cell: Generating electricity from household rice washing wastewater

The soil microbial fuel cell (SMFC) is a potential technology for bioelectricity generation. An SMFC can convert chemical energy from organic compounds to electrical energy by utilizing exoelectrogenic bacteria existing in the soil. However, the conventional SMFC configuration is hard to set up and inconvenient to use. In addition, rice is one of the main staple foods worldwide, especially in Asia. Rice washing wastewater (RWW) contains various organic compounds with starch, minerals, and vitamins. In this study, a new design of a compact, portable, membrane-less SMFC is proposed. The SMFC is low-cost, easy-to-use, and can generate bioelectricity from abundant household RWW. The SMFC with double carbon-based anode and cathode electrodes was evaluated in muddy soil (total carbon (TC): 85,200 mg/kg, pH: 4.5, and electrical conductivity (EC): 1.36 dS/m) and sandy soil (TC: 1970 mg/kg, pH: 6.6, and EC: 0.01 dS/m) in an incubator at 30 +/- 2 celcius. Household RWW was used as a carbon source to feed bacteria in the soil to power the SMFC. For comparison, a control experiment was also conducted, where only water was added to maintain the soil humidity. 15 mL of RWW or water was added to the SMFCs every 48 h. The result showed that when muddy soil was used, the maximum power density of the SMFC with RWW supplied was 485.2 mW/m2, which was 2.4 times higher than the controlled SMFC (202.9 mW/m2). When sandy soil was used, the SMFC with RWW supplied generated the maximum power density of 112 mW/m2, while that of the controlled SMFC was almost zero. These results imply that the proposed SMFC can operate in different types of soil and effectively generate bioelectricity from RWW.

Automated summary

This study proposes a new design of a compact, portable, membrane-less soil microbial fuel cell (SMFC) that can generate bioelectricity from household rice washing wastewater (RWW). The experimental results show that the SMFC can operate in different types of soil and effectively generate bioelectricity from RWW.