Development of Microbial Fuel Cells (MFCs) using Efficient Acclimation and Various Substrates

Open Access
Author:
Kim, JungRae
Graduate Program:
Environmental Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
August 29, 2006
Committee Members:
  • Bruce Ernest Logan, Committee Chair
  • John Michael Regan, Committee Member
  • Rachel Alice Brennan, Committee Member
  • Ming Tien, Committee Member
  • Peggy Ann Johnson, Committee Member
Keywords:
  • Microbial Fuel Cell
  • MFC
  • enrichment
  • alcohol
  • membrane
  • animal swine wastewater
Abstract:
Microbial fuel cells (MFCs) are an emerging technology which convert organic matter to electricity using a fixed biofilm on the electrode as the biocatalyst. It has recently been shown that a new wastewater treatment method based on microbial fuel cells (MFCs) can be used to treat domestic or industrial organic wastewater and simultaneously produce electricity. Sewage sludge has been known to be a good inoculum for MFCs because it can be readily obtained and contains various electrochemically active microbes. Various techniques to enrich electrochemically active bacteria on an electrode using anaerobic sludge as an inoculum were studied using anaerobic sludge and a two-chamber fuel cell. A ferric oxide coated electrode increased power density and coulombic efficiency to 30 mW/m2 and 80%, as compared with carbon electrode (8 mW/m2 and 40%). The methanogen inhibitor (2-bromoethanesulfonate; BES) also increased the CE to 70%. A paste of bacteria from an electrode already producing electricity for a new electrode increased the power density to 40 mW/m2. These results indicate that sewage sludge can be used as an inoculum with the proper acclimation techniques to increase the effectiveness of electricity generation using domestic or industrial wastewater. Alcohols are believed to be transient liquid fuels for hydrogen fuels cell due to easy storage and transportation. Microbial fuel cells (MFCs) using microorganisms as a biocatalyst have not been reported. The maximum power density and CE using ethanol in a 2-chamber MFC system were 40 mW/m2 at 0.3 mA and 42% to 61%, respectively. The result of the byproduct analysis indicated that ethanol was oxidized to CO2 via acetate. Single chamber MFCs with air cathodes using ethanol produced the maximum power density of 488 ¡¾ 12 mW/m2 and approximately 10% of CE. The community analysis result from 16S rDNA-based techniques indicate Proteobacterium Core-1 (33.3% of clone library sequences), Azoarcus sp. (17.4%), and Desulfuromonas sp. M76 (15.9%) were significant members of the anode chamber community. The polymer electrolyte membranes (PEMs) for Microbial Fuel Cells (MFCs) are critical to increase fuel efficiency and power density but they have not been studied extensively. The physical properties (oxygen and acetate diffusion coefficients) of commonly used MFC membranes, such as Nafion¢ç 117, CMI-7000, AMI-7001, Hydro-Ion and three UF membranes (molecular cut-off, 0.5K, 1K and 3K), were tested. Internal resistances of the membranes were monitored with the impedence analysis using a potentiostat. The coulombic loss by the diffusion and the biomass production in MFC was estimated by the mass balance of acetate. The maximum power densities and Coulombic efficiency were obtained from the MFCs employed with AMI-7001 (609.8 mW/m2) and CMI-7000 (76.9%), respectively.