Use of waste glycerol as fuel in microbial fuel cells (MFCs) would result in the production of valuable metabolites and electricity, to the benefit of biodiesel operations. In this research, the effect of salt and other compounds found in waste glycerol from biodiesel production on the metabolism and performance of three cultures (Escherichia coli W3110, Propionibacterium freudenreichii ssp. shermanii and mixed culture AR2), used as anodic catalysts in an MFC was studied. MFC experiments were performed in parallel with serum bottle fermentations to allow for comparison of glycerol consumption and metabolite yield. The effect of salt content on the performance of all three cultures was positive in most cases and negligible in others. Using waste glycerol with an increased concentration of other compounds (other than salt) only reduced the performance of AR2, however an inhibitory effect on the rate of glycerol consumption was observed with both AR2 and P. freudenreichii ssp. shermanii. For all strains, the rate of glycerol consumption was slower in MFCs than in fermentations as a result of the electrochemical environment; the yield of various metabolites also differed.

Use of waste glycerol as fuel in microbial fuel cells (MFCs) would result in the production of valuable metabolites and electricity, to the benefit of biodiesel operations. In this research, the effect of salt and other compounds found in waste glycerol from biodiesel production on the metabolism and performance of three cultures (Escherichia coli W3110, Propionibacterium freudenreichii ssp. shermanii and mixed culture AR2), used as anodic catalysts in an MFC was studied. MFC experiments were performed in parallel with serum bottle fermentations to allow for comparison of glycerol consumption and metabolite yield. The effect of salt content on the performance of all three cultures was positive in most cases and negligible in others. Using waste glycerol with an increased concentration of other compounds (other than salt) only reduced the performance of AR2, however an inhibitory effect on the rate of glycerol consumption was observed with both AR2 and P. freudenreichii ssp. shermanii. For all strains, the rate of glycerol consumption was slower in MFCs than in fermentations as a result of the electrochemical environment; the yield of various metabolites also differed.

Une pile à combustible microbiennes (PCM) est un dispositif capable de produire de l’énergie électrique à partir d’énergie chimique grâce à l’activité catalytique des bactéries en présence de combustibles organiques. Ces travaux de thèse ont eu pour objectif la synthèse des nouveaux matériaux d’anode et de cathode qui pourraient constituer des alternatives aux matériaux à base de platine. Coté anode, nous avons synthétisé des matériaux par précipitation chimique sur du graphite en poudre à partir de mélanges contenant des ions ferreux et sulfures. Les caractérisations physicochimiques ont montré la formation de composés soufrés (mackinawite, polysulfures et soufre élémentaire) qui se transforment en produits soufrés plus oxydés en présence d’air. La formation de vivianite a été confirmée dans le cas d’un excès d’ions ferreux par rapport aux ions sulfures. Les analyses électrochimiques montrent que ces matériaux ont un comportement réversible avec des densités de courant d’oxydation élevées à bas potentiel. Coté cathode, nous avons choisi la synthèse par voie électrochimique d’un film de MnOx sur substrat d’acier inoxydable. Les caractérisations physicochimiques ont démontré la formation de la birnessite. Les analyses électrochimiques montrent que la réduction de ce matériau conduit à des courants cathodiques significatifs mais avec une réversibilité limitée, même en présence d’air. La réalisation de prototypes de PCM dans lesquels l’anode à base de composés soufrés est immergée dans une solution de terreau et la cathode à base de MnOx est au contact de l’air, a permis d’obtenir des puissances instantanées maximales de l’ordre de 12 W.m-3 et 1,8 W.m-2, et des densités de courant de l’ordre de 25 A.m-3 et 3,8 A.m-2. Un travail d’optimisation du fonctionnement de PCM a été réalisé. Ainsi, l’augmentation de la conductivité de la solution anodique et la diminution de quantité de sédiment dans la solution de terreau a permis d’améliorer la réponse électrochimique du matériau anodique et d’obtenir des puissances instantanées maximales de l’ordre de 17,5 W.m-3 et 2,7 W.m-2, et des densités de courant de l’ordre de 60 A.m-3 et 9,2 A.m-2. Le facteur limitant reste toujours le comportement électrochimique du film de MnOx. / A microbial fuel cell (MFC) is a device allowing the production of electric power from chemical energy thanks to the catalytic activity of bacteria in presence of organic fuel. These works aimed the synthesis of new anode and cathode materials which could be an alternative to platinum materials. On the anode side, we synthesized the materials by chemical precipitation on powder graphite from mixtures containing ferrous and sulfide ions. Physicochemical characterizations showed the formation of sulfur compounds (mackinawite, polysulfide and elementary sulfur) which transform into sulfur products more oxidized in presence of air. Formation of vivianite was confirmed in the case of an excess of ferrous ions in relation to sulfide ions. Electrochemical analysis shows that these materials have a reversible behavior with high current densities at low voltage. On the cathode side, we chose electrochemical synthesis of an MnOx film on stainless steel substrate. Physicochemical characterizations showed birnessite formation. Electrochemical analysis show that the reduction of this material Leeds to significative cathodic currents but with a limited reversibility, even in presence of air. The realization of MFC prototypes in which the sulfur compounds-based anode is submerged in compost solution and the MnOx-based cathode is in contact with air, allowed the getting of maximum instantaneous powers on the order of 12 W.m-3 and 1,8 W.m-2, and current densities on the order of 25 A.m-3 et 3,8 A.m-2. An optimization work of the MFC functioning has been done. So, the conductivity increase of the anodic solution and the decrease of sediment quantity in the compost solution allowed the improvement of the electrochemical response of the anodic material and to obtain maximal instantaneous powers on the order of 17,5 W.m-3 and 2,7 W.m-2, and current densities on the order of 60 A.m-3 et 9,2 A.m-2. The limiting factor remains the electrochemical behavior of the MnOx film.

Using glycerol from biodiesel production as a fuel in a microbial fuel cell (MFC) will generate electricity and valuable by-products from what is currently considered waste. This research aims to screen E. coli (W3110, TG1, DH5, BL21), P. freudenreichii (subspecies freudenreichii and shermanii), and mixed cultures enriched from compost (AR1, AR2, AR3) as anodic biocatalysts in a glycerol-oxidizing MFC. Anaerobic fermentation experiments were performed to determine the oxidative capacity of each catalyst towards glycerol. Using an optimized medium for each strain, the highest anaerobic glycerol conversion from each group was achieved by E. coli W3110 (4.1 g/L), P. freudenreichii ssp. shermanii (10 g/L), and AR2 (20 g/L). These cultures were then tested in an MFC system. All three catalysts exhibited exoelectrogenicity. The highest power density was achieved using P. freudenreichii ssp. shermanii (14.9 mW m-2), followed by AR2 (11.7 mW m-2), and finally E. coli W3110 (9.8 mW m-2).

An air cathode, membrane-less microbial fuel cell (MFC) containing a co-culture of Geobacter sulfurreducens and Escherichia coli was constructed and compared to pure culture MFCs of both organisms. The E. coli containing MFCs were unsparged and relied on E. coli for oxygen removal. The pure G. sulfurreducens MFC had a power output of 128 mW/m2, compared to 63 mW/m2 for the co-culture at an early stage and 56 mW/m2 for the late stage co-culture. The limiting current density is 404 mA/m2 for the pure G. sulfurreducens culture, 184 mA/m2 for the early co-culture, and 282 mA/m2 for the late co-culture, despite an increase in internal resistance between the early and late co-culture cells. Analysis of metabolites has shown that succinate production is likely to have negatively affected current production by G. sulfurreducens, and the removal of succinate is responsible for the increased current density in the late co-culture cell.

An air cathode, membrane-less microbial fuel cell (MFC) containing a co-culture of Geobacter sulfurreducens and Escherichia coli was constructed and compared to pure culture MFCs of both organisms. The E. coli containing MFCs were unsparged and relied on E. coli for oxygen removal. The pure G. sulfurreducens MFC had a power output of 128 mW/m2, compared to 63 mW/m2 for the co-culture at an early stage and 56 mW/m2 for the late stage co-culture. The limiting current density is 404 mA/m2 for the pure G. sulfurreducens culture, 184 mA/m2 for the early co-culture, and 282 mA/m2 for the late co-culture, despite an increase in internal resistance between the early and late co-culture cells. Analysis of metabolites has shown that succinate production is likely to have negatively affected current production by G. sulfurreducens, and the removal of succinate is responsible for the increased current density in the late co-culture cell.

Microbial fuel cells (MFCs) are emerging energy production technology which converts the chemical energy stored in biologically degradable compounds to electricity at high efficiencies. Microbial fuel cells have some advantages such as use of an inexpensive catalyst, operate under mild reaction conditions (i.e. ambient temperature, normal pressure and neutral pH), and generate power from a wide range and cheap raw materials. These make microbial fuel cell as an attractive alternative over other electricity generating devices. However, so far the major problem posses by this technology is the low power outputs of the microbial fuel cells that hinder its commercialization. Restriction in the electron transfer from bacteria to the anode electrode of a MFC is thought to be one cause for the low power output. Most recent MFC research is focused on using contaminants present in industrial, agricultural, and municipal wastewater as the energy source, with very few studies utilising gaseous substrates. Mediators can be added to MFCs to enhance the electron transfer from the microbe to the anode, but have limited practical applicability in wastewater applications because of the difficulty in recovering the expensive and potentially toxic compound. This thesis describes an investigation of electricity generation in a microbial fuel cell by combining a gaseous substrate with a mediator in the anode compartment. The emphasis being placed on the selection of a mediator to improve the electron transfer process for electricity production in an MFC. Subsequently, methods to improve the performance of a mediator MFC in respect of power and current density were discussed. This type of MFC is purposely aimed to be applied for treating gaseous contaminants in an anaerobic biofilter while simultaneously produce electricity. In this study, ethanol was the first gaseous substrate tested for the possibility to generate electricity in the MFC. Various mediators were previously compared in their reversibility of redox reactions and in the current production, and three best mediators were then selected for the power production. The highest electrical current production i.e. 12 μA/cm2 was obtained and sustained for 24 hrs with N,N,N',N'-tetramethyl-1,4- phenylendiamine TMPD (N-TMPD) as the mediator using glassy carbon (GC) electrode. The maximum power density reached 0.16 mW/cm2 by using carbon cloth (CC) anode. The absorption of these mediators by the bacterial cells was shown to correlate with the obtained energy production, with no N-TMPD was absorbed by the bacterial cells. The 24 hr current production was shown to be accompanied by the decrease in the ethanol concentration (i.e. 1.82 g/L), however ethanol crossover through the proton exchange membrane and ethanol evaporation around the electrodes were most likely to be the major cause of the decrease in the ethanol concentration. A theoretical coulombic efficiency of 0.005% was calculated for this system. The electrokinetics of microbial reduced mediator in the ethanol-mediator MFCs was also examined. Two methods i.e. linear sweep voltammetry (LSV) and cyclic voltammetry (CV) were used to obtained the kinetic parameters. CV method gave a better estimation of the kinetic parameters than LSV method due to the low concentration of the mediators used, affecting the Tafel behaviors. All CVs showed quasi-reversible behaviors compared to the CVs in the absence of the bacteria, which is thought due to the bacteria decreased the amount of the reduced and the oxidised mediator available at the surface of GC electrode. The highest exchange current density (i o ) was obtained by using N-TMPD as the mediator with the same concentration of the mediator used i.e. 0.13±0.01 mA/cm 2. The power output achieved also the highest (0.008 mW/cm 2) with N-TMPD as the mediator. The power density was improved to 0.03 mW/cm2 by using CC electrode. Another main objective of this thesis is to prove anoxic methane oxidation which was believed to occur only in marine sediments, and applies this for power generation in microbial fuel cells. Ferricyanide looked promising when it was used as the electron acceptor (thus as the mediator for the MFC). It was shown that ferricyanide was fully reduced by methanotrophs bacteria with methane as the substrate (versus abiotic and nitrogen control). The highest reduction rate achieved was 3 x10-3 mM/min.g. This finding was supported by ferricyanide peak heights disappearance (spectrophotometry at 420 nm), CO 2 production (sensor readings), ferrocyanide formation (cyclic voltammetry), and no other alternate electron acceptor was present. The total CO 2 produced was equal to 0.015 mmoles of CO 2 from starting concentration ferricyanide of 0.2 mmoles (after substraction with an offset value). CV results show 2.4 mM of ferrocyanide was produced after a total addition of 3 mM ferricyanide into the anoxic methanotrophic suspension. The current and voltage generation in microbial fuel cell reactor from the reduced ferricyanide confirmed that ferricyanide received electrons from the bacterial metabolism. The maximum power density of 0.02 mW/cm2 and OCV of 0.6 V were obtained with 3 mM ferricyanide using LSV method.

Using glycerol from biodiesel production as a fuel in a microbial fuel cell (MFC) will generate electricity and valuable by-products from what is currently considered waste. This research aims to screen E. coli (W3110, TG1, DH5, BL21), P. freudenreichii (subspecies freudenreichii and shermanii), and mixed cultures enriched from compost (AR1, AR2, AR3) as anodic biocatalysts in a glycerol-oxidizing MFC. Anaerobic fermentation experiments were performed to determine the oxidative capacity of each catalyst towards glycerol. Using an optimized medium for each strain, the highest anaerobic glycerol conversion from each group was achieved by E. coli W3110 (4.1 g/L), P. freudenreichii ssp. shermanii (10 g/L), and AR2 (20 g/L). These cultures were then tested in an MFC system. All three catalysts exhibited exoelectrogenicity. The highest power density was achieved using P. freudenreichii ssp. shermanii (14.9 mW m-2), followed by AR2 (11.7 mW m-2), and finally E. coli W3110 (9.8 mW m-2).

Using glycerol from biodiesel production as a fuel in a microbial fuel cell (MFC) will generate electricity and valuable by-products from what is currently considered waste. This research aims to screen E. coli (W3110, TG1, DH5, BL21), P. freudenreichii (subspecies freudenreichii and shermanii), and mixed cultures enriched from compost (AR1, AR2, AR3) as anodic biocatalysts in a glycerol-oxidizing MFC. Anaerobic fermentation experiments were performed to determine the oxidative capacity of each catalyst towards glycerol. Using an optimized medium for each strain, the highest anaerobic glycerol conversion from each group was achieved by E. coli W3110 (4.1 g/L), P. freudenreichii ssp. shermanii (10 g/L), and AR2 (20 g/L). These cultures were then tested in an MFC system. All three catalysts exhibited exoelectrogenicity. The highest power density was achieved using P. freudenreichii ssp. shermanii (14.9 mW m-2), followed by AR2 (11.7 mW m-2), and finally E. coli W3110 (9.8 mW m-2).

3D printing has revolutionised traditional manufacturing methods, opening up and distributing design and production of low cost, custom objects to virtually anyone. Tailoring of print material and part geometry allows for the benefits of this technology to reach multiple engineering and scientific fields, given appropriate design. A multidisciplinary approach concerning development of new print materials and methods was undertaken with the aim of further expansion and application of 3D printing towards electrochemical applications. Specific requirements of materials used in this domain, such as conductivity and chemical stability, led to development of functional printable carbon composites, compatible with consumer grade 3D printers. This allows facile production of cheap, reusable, disposable, electrodes for analytical applications, demonstrating heavy metal detection in aqueous media and allowing further tailoring to specific applications to be easily implemented. A new method for printing of cellulose solutions was developed, with post processing of printed parts resulting in biocompatible, porous, conductive structures. When used as electrodes in microbial fuel cells, improved power and current output over traditionally used carbon cloth electrodes was achieved. Other developments resulting from this work applicable to other fields include a novel trajectory generation method based on exponential functions which can be applied to practically any robotic system, as well as improvements to the production process of metal alloy filaments for 3D printing of metallic components.