Harvesting electricity from the organic fraction of municipal solid waste using microbial fuel cells - by Joline Raymond El Chakhtoura.

Abstract

Global trends linking population and economic growth to ecological security highlight the urgency of developing renewable, carbon-neutral energy technologies. A microbial fuel cell (MFC) is such an environmental biotechnology that exploits microorganisms (pure or mixed seed) in the catalytic conversion of organic matter (simple or complex substrate) to electrical energy. In developing countries, where solid waste management is a major challenge, the organic fraction of municipal solid waste (OFMSW) is an abundant, potentially attractive source of biomass energy. The objective of this thesis was to test the potential of direct power generation from OFMSW-fed MFCs by exploring a variety of inocula; wastewater sludge, cattle manure and rumen microorganisms. To achieve this objective, nine cube-shaped, single-chambered, air-cathode MFCs were constructed using carbon cloth electrodes. The OFMSW (domestic food waste) was collected and processed to obtain a feed with particles of size 0.3-0.85 mm. The MFCs were initially fed glucose and inoculated with wastewater sludge (10% v/v), operating in fed-batch mode until a stable voltage was reached. Then, the glucose solution was replaced with a diluted solution of OFMSW and six of the MFCs were inoculated with either cattle manure or rumen microorganisms (10% v/v). The performance of the nine MFCs (triplicate MFCs for each type of seed) was evaluated at different chemical oxygen demand (COD) concentrations (1178, 3555 and 6605 mg/L) in terms of power density, Coulombic efficiency (CE) and organic removal. At low COD, the wastewater and manure-seeded MFCs performed better than the rumen-seeded MFCs. Power density reached 122 mW/m2 and CE reached 24%, values comparable to other MFC studies utilizing complex substrates. COD removal reached 88%, higher than what has been reported with complex substrates. Upon increasing the organic loading, the performance of all the MFCs declined, possibly due to catalyst exhaustion, biofilm growth and/or a drop in pH. This thesis corroborates the potential of power generation from OFMSW-fed MFCs, but extensive research is needed involving the long-term stability and upscale of such systems.