Microbial fuel cells (MFCs) are novel green technologies that convert chemical energy stored in biomass into electricity through microbial metabolisms. Both fossil fuel depletion and environmental concern have fostered significant interest in MFCs for both wastewater treatment and electricity generation. However, MFCs have not yet been used for practical applications due to their low power outputs and challenges associated with scale-up. High throughput screening devices for parallel studies are highly necessary to significantly improve and optimize MFC working conditions for future practical applications. Here in this research, microfabricated platforms of microbial fuel cell array as high throughput screening devices for MFC parallel studies have been developed. Their utilities were described with environmental sample screening to uncover electricigens with higher electrochemical activities. The first version of the MFC arrays is a batch-mode miniaturized 24-well MFC array using ferricyanide as catholyte. Several environmental species that showed higher electricity generation capabilities than Shewanella oneidensis MR-1 (SO) were uncovered using the developed MFC array, with one environmental electricigen, Shewanella sp. Hac353 (dq307734.1)(7Ca), showing 2.3-fold higher power output than SO. The second MFC array platform developed is an air-cathode MFC array using oxygen in air as electron acceptor, which is sustainable compared to ferricyanide that depletes over time. Environmental electricigen screenings were also conducted, showing parallel comparison capabilities of the developed array. The third MFC array platform is a microfluidic-cathode MFC array that enables long-term operations of miniature MFC arrays with improved power generation abilities. The capability of the microfluidic-cathode MFC array to support long-term parallel analysis was demonstrated by characterizing power generation of SO and 7Ca, proving extended operation time and improved power outputs compared to batch-mode MFC array. The fourth MFC array platform enables both catholyte and anolyte replenishments for long-term characterization of various carbon substrate performances. Finally, the 24-well microfluidic MFC array was further scaled up to 96 wells, which greatly increased the throughput of MFC parallel studies. The developed MFC arrays as high throughput screening platforms are expected to greatly impact how current MFC studies are conducted and ultimately lead to significant improvement in MFC power output.

Thesis (M.S.)--Missouri University of Science and Technology, 2009. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed August 10, 2009) Includes bibliographical references (p. 58-64).

Σε μια μικροβιακή κυψελίδα καυσίμου (ΜΚΚ), τα βακτήρια που οξειδώνουν την οργανική ύλη συγκρατούνται ξεχωριστά από τον δέκτη ηλεκτρονίων μέσω μιας μεμβράνης ανταλλαγής πρωτονίων (ΜΑΠ). Τα ηλεκτρόνια περνούν από τα βακτήρια στο ηλεκτρόδιο (άνοδος) που βρίσκεται στον ίδιο θάλαμο με αυτά και στη συνέχεια διοχετεύονται μέσω κυκλώματος στην κάθοδο όπου συνδυάζονται με πρωτόνια και οξυγόνο για να σχηματίσουν νερό. Η διαφορά στο δυναμικό εξαιτίας της ροής των ηλεκτρονίων παράγει το ηλεκτρικό ρεύμα σε αυτή την κυψελίδα καυσίμου. Σε πρώτη φάση, λοιπόν, η ΜΚΚ περιλαμβάνει συνθετικό μέσο βασισμένο στη γλυκόζη ως καύσιμο και οξυγόνο ως δέκτη ηλεκτρονίων με τεχνητό φορέα ηλεκτρο-νίων και στη συνέχεια γίνεται εμπλουτισμός με ηλεκτροχημικά βακτήρια. Προσδιορίζονται οι βασικοί παράγοντες που επιδρούν περιοριστικά στην παραγωγή ηλεκτρικού ρεύματος. Οι συνήθεις περιοριστικοί παράγοντες είναι η χαμηλής απόδοσης μεταφορά ηλεκτρονίων από τα κύτταρα στα ηλεκτρόδια, η διέλευση του οξυγόνου μέσω της μεμβράνης επιτρέποντας την αερόβια ανάπτυξη των μικροοργανισμών, το φράξιμο της μεμβράνης και η μικρή επιφάνεια της ανόδου που περιορίζει την απελευθέρωση των ηλεκτρονίων από την άνοδο (Liu et al., 2004; Kim et al., 2004). / -

Microbial fuel cell (MFC) systems capable of both treating wastewaters and recovering energy have the potential for successful scale-up as a low carbon technology. These systems utilize microorganisms residing in biofilms as biocatalytic agents in the conversion of reduced substrates to electrical energy. As such, it is important to understand how MFC anodic biofilms develop over time and also how environmental parameters such as substrate type, temperature, carbon support material, anode architecture and optimized applied potentials also affect electrogenic performance. The type of substrate was found to have a large impact on the acclimation and performance of electrogenic biofilms. Acetate produced the highest power density of 7.2 W m 3 and butyrate the lowest at 0.29 W m"3, but it was also found that biofilm acclimation to these different trophic conditions also determined the MFC response to different substrate types i.e. both acetate and butyrate substrates produced power densities of 1.07 and 1.0 W m"3 respectively in a sucrose enriched reactor. The use of MFCs for wastewater treatment in temperate regions requires the development of reactor systems that are robust to seasonal fluctuations and are energy efficient. As such, system performance was examined at three different operating temperatures (10°C, 20°C and 35°C). At each temperature a maximum steady-state voltage of 0.49 V ± 0.02V was achieved after an operational period of 47 weeks, with the time to reach steady-state voltage being dependent on acclimation temperature. The highest COD removal rates of 2.98g COD L^d * were produced in the 35°C reactor but coulombic efficiencies (CE) were found to be significantly higher at pyschrophilic temperatures. Acclimation at different operating temperatures was found to a have a significant effect on the dynamic selection of psychrophilic, psychrotolerant and mesophilic anode respiring bacteria (ARB) and also influence the development of biofilm biomass, methanogenesis and electrogenic activity. Although start-up times were inversely influenced by temperature the amount of biomass accumulation increased with higher operational temperatures and this had a direct impact on biocatalytic performance. The three dimensional structure and porosity of different carbon anode materials affected anodic performance by determining the levels of surface area available for biofilm growth and the capacity for mass transfer to occur. Novel helical electrode configurations were used to look at the effect of altering turbulent flows to increase mass transfer rates and carbon surface areas available for electrogenic growth. The spiral with the highest amount of carbon veil and the smallest gap produced the highest power production of 11.63 W m"3 . Comparative studies of a logic controlled and un-controlled external load impedance showed that control affected the biocatalyst development and hence MFC performance. The controlled MFC better optimized the electrogenic anodic biofilm for power production, indicating that improved power and substrate conversion can be achieved by ensuring sustainable current demand, applied microbial selection pressures and near-optimal impedance for power transference.

A key engineering challenge is a transition to cleaner sustainable energy supply that is derived from renewable resources. Furthermore, affordable access to this modern sustainable energy services for communities in particular poor rural and urban communities is crucial. Microbial fuel cell (MFCs) is an emerging renewable alternative technology with potential to be self-sustaining that could alleviate the energy crisis and reduce environmental pollution. The use of the MFC as a dual system for electricity generation and wastewater treatment is been well reported in literature. Manganese dioxide (MnO2) is an effective electro-catalyst that have been used for alkaline fuel cells and battery application. MnO2 have a high conductivity and high structural porosity for ion and gas transport. In addition, MnO2 have a favourable crystal morphology, which makes it particularly useful for improving oxygen reduction reaction in the fuel cell. Graphene (GO) will be loaded on MnO2 surface as an effective support material. GO is a material good for electrical conductivity and their mechanical strength is applicable in electro-catalytic activities and is cost effective. In this work, a constructed dual chamber MFC configuration with graphite rod electrodes, MnO2-GO electrocatalyst and proton exchange membrane (PEM) using municipal sewage wastewater to generate electricity. The MnO2 as an alternative electro catalyst used for oxygen reduction reaction (ORR) in the MFC while using reduced graphene (rGO) as a support to enhance electrode surface area. Also addressing the effect of graphene material loading on MnOx catalyst for electrochemistry. The characterization of the MnO2-GO electrocatalyst have been analysed using X-Ray diffraction (XRD), Brunau-Emmett-Teller (BET) surface area and Fourier transform infrared spectroscopy (FTIR) for structural properties. Electrochemical techniques such as cyclic voltammetry (CV) for MnO2-GO electrocatalyst. Thermal gravimetric analysis (TGA) for the thermal properties, and the morphological properties probed by Scanning Electron Microscopy (SEM). The dual chamber MFC design functioned successfully and tested for energy generation from municipality sewage wastewater. The maximum voltage of 586 mV reached during MFC operation with various sewage municipal wastewater COD of 100-300mg/L. The maximum power density of 248 mW/m2 with resistance of 16.98 Ω and highest current density of 1.72mA/m2 was observed at the first cycle as compare to other cycle. The lowest value of 0.002159 mA/m2 obtained at the end of 10 days. The content of municipality sewage wastewater is capable of generating electricity. The physico-chemical properties of α-MnO2 exhibits excellent cycling stability on the electrochemical. This excellent cycling stability of α-MnO2 as a super capacitor electrode material. In addition, the graphene material loading on α-MnO2 has improved the electro catalytic activity, which influences the kinetics of the reduction reaction. The α-MnO2 synthesized BET analysis specific surface area of 134.61m2 g-1 reported. MFC technology has the potential to finds its own niche in the energy industry as it is becoming more and more sustainable due to the lower cost of electro catalyst materials. Power densities of 248 mW/m2 using wastewater with COD of 291mg/l were much higher than those previously obtained using low strength wastewater. These results have opened doors for further investigation of improving electro catalysis, utilized high concentration wastewater with high COD and improved MFC design including electrode materials. / Civil and Chemical Engineering / M. Tech. (Chemical Engineering)

Live green microalgae Chlorella pyrenoidosa was introduced in the anode of microbial fuel cell (MFC) to act as an electron donor. The electrogenic capability of algae Chlorella pyrenoidosa was investigated in two models of algal microbial fuel cells (MFCs) constructed with carbon electrodes and no mediator. The mechanism was studied by results of ATP inhibitor (Resveratrol) and protonophore (2, 4-dinitrophenol), which supporting the important role of mitochondria in electricity generation. The results of different light intensity and algae concentration indicate that low concentration of 106 (OD680nm) and low light intensity (2500 Lux) generated higher electricity. In the oxygen controlled study, it was found that oxygen generated by algae in anode was a limiting factor for electricity generation. Electricity generation was observed in two chamber algae MFC lasting at least for 24 hours. Results might provide a platform for the development of self-sustainable algal culturing microbial fuel cell (MFC). Electricity was found to increase in response to 4-nitrophenol (4NP) and 4-nitroanaline (4NA) for both measurements of current and open circle voltage (OCV). The positive response of algae to 4NP in increasing the 4NP production and electricity generation in MFC proposed the possible application in the detection of E.coli, as 4NP is involved in the intermediate step of the detection process. Results indicate Algae MFC was suitable for the detection of E. coli. of concentration higher than 106 using OCV measurement. Keywords: Electricity generation, Chlorella pyrenoidosa, Microbial fuel cell.

Two billion people world-wide use kerosene-burning lamps for household lighting. These lamps produce large quantities of soot. In Chapter 2, I describe our field study examining 230 people in rural Uganda. I show that kerosene lamps are a major source of smoke exposure in the developing world, and that replacing such lamps with solar-powered lights reduces indoor soot levels 17-fold, leading to significant improvements in health within months. This finding is particularly notable because respiratory disease is the #1 cause of death in children under 5 worldwide. Because solar cells are a challenge to manufacture in the developing world, I next examined the potential of harvesting electrons from soil-based microbes as a source of clean energy. Such devices are known as microbial fuel cells (MFCs); because soil is available everywhere, MFCs can, in principle, be locally constructed all over the world. In Chapter 3, I describe our exploration of the biology of MFCs, using high-throughput DNA sequencing to demonstrate a role for genus Pseudomonas in energy production. I also examine numerous agricultural products available throughout the developing world to determine whether any could serve as a suitable ‘feed’ for MFC soil. I find that dried animal blood increases MFC energy production 10-fold. In Chapter 4, I describe our design of a modular, stackable MFC, demonstrate that it can be easily constructed in rural Africa, and use it to power lights and to charge a cell phone battery.

Microbial fuel cells (MFCs) are a promising form of alternative energy capable of harnessing the potential energy stores in organic waste. The oxygen reduction reaction (ORR) forms an integral role in the generation of electricity in MFCs however it is also a potential obstacle in enhancing the performance of MFCs. Platinum, a commonly used catalyst for the ORR, is expensive and rare. Significant research has been conducted into developing alternative catalysts. Metallophthalocyanines (MPc) have garnered attention for use as catalysts. Iron phthalocyanine (FePc) has been shown to have catalytic activity towards the reduction of oxygen. Coupling of the catalyst to nanostructured carbon materials, such as multi-walled carbon nanotubes, has been observed to have several advantages as nanostructures have a high surface-to-volume ratio. In this study, we have attempted to assess the suitability of FePc, both its bulk and nanostructured form, as an oxygen reduction catalyst and acid functionalized multi-walled carbon nanotubes for use as a catalyst support using electrochemical techniques such as cyclic voltammetry and electrochemical impedance spectroscopy. We showed, for the first time, the catalytic nature of nanostructured FePc towards the ORR. Applying the data obtained from the electrochemical analyses, electrodes were modified using FePc and MWCNTs and applied to an Enterobacter cloacae-based MFC. Several operational parameters of the MFC, such as temperature and ionic strength, were optimized during the course of the study. We showed that optimized FePc:MWCNT-modified electrodes compared favourably to platinum-based electrodes in terms of power densities obtained in a microbial fuel cell.

Global increases in water demand and decreases in both the quantity and quality of fresh water resources have served as the major driving forces to develop sustainable use of water resources. One viable alternative is to explore non-traditional (impaired quality) water sources such as wastewater and seawater. The current paradigm for wastewater treatment is based on technologies that are energy intensive and fail to recover the potential resources (water and energy) in wastewater. Also, conventional desalination technologies like reverse osmosis (RO) are energy intensive. Therefore, there is a need for the development of sustainable wastewater treatment and desalination technologies for practical applications. Processes based on microbial electrochemical technologies (METs) such as microbial fuel cells (MFCs), microbial electrolysis cells (MECs) and microbial desalination cells (MDCs) hold promise for the treatment of wastewater with recovery of the inherent energy, and MDCs could be used for both desalination of seawater and energy recovery. METs use anaerobic bacteria, referred to as exoelectrogens, that are capable of transferring electrons exogenously to convert soluble organic matter present in the wastewater directly into an electrical current to produce electrical power (MFC and MDC) or biogas (MEC). In my dissertation, I investigated the three types of METs mentioned above to: 1) have a better insight on the effect of 4 oxygen intrusion on the microbial community structure and performance of air-cathode MFCs; 2) improve the desalination efficiency of air-cathode MDCs using ion exchange resins (IXRs); and 3) enrich for extremophilic exoelectrogens from the Red Sea brine pool using MECs. The findings from these studies can shape further research aimed at developing more efficient air-cathode MFCs for practical applications, a more efficient integrated IXRMDC configuration that can be used as a pre-treatment to RO, and exploring extreme environments as a source of extremophilic exoelectrogens for niche-specific applications of METs.

Hydrogen is re-emerging as a serious alternative to fossil fuels. It is a clean gas with high energy density and its combustion only generates water vapour. Nevertheless, the hydrogen industry has a significant carbon footprint since this gas is mostly derived from fossil fuels reforming processes. This project focusses on the development of sustainable alternatives to conventional hydrogen production, in which approaches based on dark fermentation (DF) using an inexpensive residue from the brewery industry as primary feedstock are presented. Firstly, a fungal pre-treatment (FT) was proposed to degrade a high-strength brewery waste slurry (BWS) to obtain an effluent with a lower concentration of chemical oxygen demand (COD) but rich in readily fermentable sugars for the ensuing DF, thus improving hydrogen yields (HY). Secondly, microbial electrolysis and fuel cells (MECs and MFCs) were proposed to assist DF, generating electricity in MFCs while improving HY by MECs. Coupling both microbial electrochemical technologies sequentially after DF did not show any advantage. However, promising results were obtained for electricity and hydrogen production when taking a single-staged approach. Treating BWS directly by MFCs produced 2.0 watts/g COD consumed, while the DF process assisted simultaneously by MECs (DF/MEC) produced 1.6 times more hydrogen than DF alone. An average HY of 2.32 ± 0.06 mol H₂/mol glucose was attained between both DF/MEC and DF after FT, hence approaching the theoretical value of 2.4 mol H₂/mol glucose, representing roughly a 50% improvement compared to DF alone. With an overall COD reduction above 76%, the DF after FT exhibited the highest energy conversion rate per substrate consumed (6.3 kJ/g COD). As valuable by-products obtained, up to 31 g/L of fungal biomass, which is appreciated in many state-of-the-art biomaterials applications, was produced by using BWS. While in the DF/MEC process, 18 g/L of butyric acid were generated, which is three times more than with DF alone. Butyric acid being the precursor to butanol and building block of biodegradable thermoplastics, this result is not without significance. The proposed approaches not only valorize BWS but also validate their economic and environmental attractiveness as promising alternative hydrogen production methods.