Introduction: Significant changes in the global ecosystem, together with a potential shortfall in oil resources, have stimulated intense interest in the development of other sources of energy, and most particularly biofuels since these are basically considered to be less harmful to human health than petroleum-based fuels. However, information about the impact of biofuel-derived vehicle emissions on human health is limited and incomplete.   Aim of the study: To identify those biofuels that are less detrimental to human health on the basis of published results from toxicological and chemical studies of vehicle emission products.   Tasks of the study: To review systematically all conventional and alternative fuels used in internal combustion engines, to identify all known toxic emission products formed by such fuels, to review their toxic effects on human health, and to analyse the data collected in order to develop conclusions concerning the possible health benefits deriving from the use of alternative fuels.   Materials and methods: In order to fulfil the requirements of a complete, comprehensive and up-to-date review of the toxic effects of automotive exhaust, an extensive search of official scientific data sources has been performed. Relevant publications were retrieved from public domain databases with a toxicological focus such as Toxcenter and CAplus, as well as from the websites of the US Environmental Protection Agency and the US Agency for Toxic Substances and Disease Registry. Keywords employed in the literature search were: petrol, gasoline, diesel exhaust, emission, biofuel, biogas, biodiesel, bioethanol, bioalcohol, toxicity, methanol and ethanol. A total of 295 references were initially selected relating to the period 1962 to 2008, and 142 of these presented titles and abstracts that met the main inclusion criteria, i.e. describing toxicological and epidemiological studies in humans. In cases where eligible studies relating to the goals and tasks of the review were limited or not available, some in vitro or in vivo toxicological studies involving animal models were included.   Results: In comparison with petroleum diesel, the emissions derived from biodiesel contain less particulate matter, carbon monoxide, total hydrocarbons and other toxic compounds including vapour-phase C1-C12 hydrocarbons, aldehydes and ketones (up to C8), selected semi-volatile and particle-phase polycyclic aromatic hydrocarbons (PAHs). Whilst sulphur-containing compounds appear to be undetectable in biodiesel, nitrogen oxide and a soluble organic fraction comprising unregulated pollutants including the “aggregated toxics” (i.e., formaldehyde, acetaldehyde, acrolein, benzene, 1,3-butadiene, ethylbenzene, n-hexane, naphthalene, styrene, toluene and xylene) are present at elevated levels. Toxicological studies have shown that the mutagenicity of exhaust particles from biodiesel is normally lower than those obtained from petroleum diesel, however, rapeseed oil-derived biodiesel exhibits toxic effects that are 4-fold greater than petroleum diesel. Such enhanced toxicity is probably caused by the presence of carbonyl compounds and unburnt fuel. The toxicity of highly volatile components of biofuel exhaust has not yet been evaluated accurately. A substantial portion of these compounds was apparently lost in the process of preparing the test samples used for the assays (during the evaporation). The overall recoveries of these compounds have not been evaluated and the accuracy of the sample preparation method has not been validated. Hence, it could be that the cytotoxic effect of biodiesel exhaust is higher than that reported. Moreover, compared with fossil diesel, fuel derived from rapeseed oil emits particulate matter with increased mutagenic effects. Epidemiological investigations of the effects of biofuels on humans are very sparse but have revealed dose-dependent respiratory symptoms following exposure to rapeseed oil biodiesel, although the observed differences between this fuel and petroleum diesel are not significant. Such data, however, give rise to serious concerns about the future usage of this plant material as a replacement for established diesel fuels. Combustion of alcohol-based fuels leads to a reduced formation of photochemical smog in comparison with gasoline or diesel, however, the emission of aldehydes (officially classified as carcinogenic or potentially carcinogenic) is several times higher. The toxicity of the exhaust emissions of gasoline-fuelled engines is generally significantly greater than that of alcohol-burning engines. However, some harmful effects from ethanol blends might be expected, such as enhanced emissions of carcinogenic PAHs and increased ozone-related toxicity associated with the high level of aldehydes emitted. The use of ethanol–diesel fuel blends gives rise to increases in regulated exhaust emissions and, possibly, to greater emissions of aldehydes and unburnt hydrocarbons. The most promising fuels, in terms of reduced toxicity and genotoxicity of exhaust emissions, are methanol-containing blends. However, the emission from these fuels still contains formaldehyde, which is a carcinogen. The use of biogas can significantly reduce emissions of total PAHs and formaldehyde and, consequently, the risk of lung toxicity. On the other hand, the emissions of particulate matter by compressed natural gas, and the mutagenic potencies of the exhaust, are similar to those associated with gasoline and diesel fuels.   Conclusions: The use of biofuel is currently viewed very favourably and there are suggestions that the exhaust emissions from such fuel are less likely to present risks to human health in comparison with gasoline and diesel emissions. However, the expectation of a reduction in health effects based on the chemical composition of biodiesel exhaust is far from reality. Thus, although toxicological evidence relating to the effects of biofuels on humans is sparse, it is already apparent that emissions from the combustion of biofuel and blends thereof with petroleum-based fuels are toxic. In addition to the regulated toxic compounds, such as total hydrocarbons, carbon monoxide, nitrogen oxides, particulate matter and polycyclic aromatic hydrocarbons, biofuel emissions contain significant amounts of various other harmful substances that are not regulated, e.g. carbonyls (including formaldehyde, acetaldehyde, benzene, 3-butadiene, acrolein, etc.). Whilst biofuels may be potentially less damaging to human health than petroleum fuels, considerable harmful effects must still be expected. Substitution of conventional fuel by biofuel decreases the concentration of regulated toxic pollutants in vehicle exhaust, but increases the concentration of some unregulated toxic pollutants emitted from on-road engines. Generally, the toxicity of biofuels decreases in the order biodiesel>biogas>ethanol>=methanol. In this respect, methanol produced by the oxidation of biogas appears to represent an alternative fuel that exhibits the least potential for damage to human health, however, this alcohol represents a source of formaldehyde pollution and is carcinogenic. .

Det här arbetet bygger på en litteraturstudie från föregående arbeten som handlar om biobränslet HVO och dess funktion vid drift av flera olika typer av dieselmotorer. Författarna till arbetet har tittat på de för- och nackdelar som föreligger vid drift på HVO och gjort jämförelser med diesel och HFO vilka dominerar inom sjöfarten idag. Arbetet har gjorts med fokus på teknisk drift samt miljöaspekter vid användning och vi har bortsett från annat som tillgång, framställning och distribution. Vi har även tagit upp kommande utsläppskrav inom sjöfarten och diskuterat vad som kan behöva göras för att klara av dessa. Skillnader i utsläpp vad gäller koldioxid, kväveoxider, svaveloxider och partiklar behandlas tillsammans med driftsaspekter som prestanda, bränsleförbrukning och lagringsstabilitet. Sett till sin helhet har resultaten visat sig vara goda för HVO vid jämförelser mot diesel och HFO, särskilt ur ett miljöperspektiv. Det största dilemmat i dagsläget är huruvida man ska kunna tillgodose de enorma behoven som råder på bränsle, då råvarutillgången är begränsad och framställningsmetoderna kostsamma. / This work is based on a literature study from previous work regarding the biofuel HVO and its function in the operation of several different types of diesel engines. The authors of this work have looked at the pros and cons of operating at HVO and made comparisons with diesel and HFO which dominate in shipping today. The work has been done with a focus on technical operations and environmental aspects in use and we have not taken availability, production and distribution into consideration. We have also raised future emission requirements in shipping and discussed what may be needed to cope with these. Differences in carbon dioxide, nitrogen oxides, sulfur oxides and particulate emissions are treated together with operational aspects such as performance, fuel consumption and storage stability. In summary, the results have proven to be in favor for HVO in comparison to diesel and HFO, especially from an environmental perspective. The biggest dilemma at present is whether to meet the enormous needs of fuel, as raw materials are limited and the production methods costly.

This research investigated life cycle environmental impacts and benefits of an integrated microalgae system with wastewater treatment system using an integrated process modeling approach combined with experimentation. The overall goal of this research is to understand energy, carbon and nutrient balances in the integrated system and to evaluate the environmental impacts and benefits of the integrated system from a carbon, nutrient, and energy perspective. In this study, four major research tasks were designed to contribute to a comprehensive understanding of the environmental and economic sustainability of the integrated system, which included development of an integrated co-limitation kinetic model for microalgae growth (Chapter 2), kinetic parameter estimation models for anaerobic co-digestion (Chapter 3), development of an integrated process model (Chapter 4), and life cycle environmental and economic assessments of the integrated system (Chapter 5). The integrated co-limitation kinetic model was developed to understand microalgae growth in the centrate from dewatering of anaerobically digested sludge. This growth kinetic model considered four major growth factors, including Nitrogen (N), dissolved carbon dioxide (CO2) concentrations, light intensity, and temperature. The model framework was constructed by combining threshold and multiplicative structures to explain co-limitation among these factors. The model was calibrated and validated using batch studies with anaerobically digested municipal sludge centrate as wastewater source, and the model was shown to have a reasonable growth rate predictor for Chlorella sp. under different nutrient levels of the centrate. Anaerobic co-digestion was used for energy conversion process in the integrated system. To estimate methane production of anaerobic co-digestion, kinetic models commonly applied. To apply the kinetic model, determining kinetic parameters for anaerobic co-digestion of microalgae and waste activated sludge (WAS) is essential, and this research introduced two potential regression-based parameter estimation models to estimate the kinetic parameters. Using the estimation models presented, the kinetic parameters for co-digestion was able to be determined for different ratios of co-substrates with limited experiments. In this research, the integrated process model was developed to simulate the dynamic behavior of the integrated system. The model included the microalgae cultivation, harvesting, and anaerobic co-digestion processes in the integrated system to provide a comprehensive understanding of the integrated system. For cultivation, the integrated co-limitation kinetic model was applied to estimate microalgae productivity, while the regression-based parameter estimation model was used to determine the first order kinetic parameter to estimate methane production rates for anaerobic co-digestion. The simulated microalgae productivity results were comparable to typical microalgae productivity in open pond systems. For the integrated system, removal of NH4-N by microalgae was not efficient. In particular, the NH4-N removal was minimal during the winter season due to low microalgae growth. As the microalgae productivity increased, the CH4 and biosolids production increased as a result of the increased amount of the substrates from the harvested microalgae biomass. The increase of CH4 and biosolids productions, however, was minor because of the small amount of microalgae biomass for the co-digestion. Based on simulated data for integrated process modeling, the life cycle environmental and economic impacts of the integrated system (with different CO2 supply areas) were evaluated and compared to the conventional wastewater treatment system. The integrated systems had a lower carbon footprint, cumulative energy demand, and life cycle cost than the conventional system. The integrated system with 10% CO2 sparging area was able to achieve the lowest carbon footprint. Without CO2 addition during microalgae cultivation, the integrated system had the lowest energy balance and life cycle cost. However, there is no significant difference between the integrated and conventional systems for eutrophication potential because these systems had the same effluent quality. In terms of an energy saving with the integrated systems, the benefit of energy reduction for the wastewater treatment was greater than the energy production from the anaerobic co-digestion, compared to the conventional system. Overall, the integrated system can improve the carbon balance by reducing the life cycle energy required in the conventional system.

Microorganisms are capable of producing advanced biofuels that can be used as ‘drop-in’ alternatives to conventional liquid fuels. However, vital physiological processes and membrane properties are often disrupted by the presence of biofuel and limit the production yields. In order to make microbial biofuels a competitive fuel source, finding mechanisms for improving resistance to the toxic effects of biofuel production is vital. This investigation aims to identify resistance mechanisms from microorganisms that have evolved to withstand hydrocarbon-rich environments, such as those that thrive near natural oil seeps and in oil-polluted waters. First, using genomic DNA from Marinobacter aquaeolei, we constructed a transgenic library that we expressed in Escherichia coli. We exposed cells to inhibitory levels of pinene, a monoterpene that can serve as a jet fuel precursor with chemical properties similar to existing tactical fuels. Using a sequential strategy of a fosmid library followed by a plasmid library, we were able to isolate a region of DNA from the M. aquaeolei genome that conferred pinene tolerance when expressed in E. coli. We determined that a single gene, yceI, was responsible for the tolerance improvements. Overexpression of this gene placed no additional burden on the host. We also tested tolerance to other monoterpenes and showed that yceI selectively improves tolerance. Additionally, we used genomic DNA from Pseudomonas putida KT2440, which has innate solvent-tolerance properties, to create transgenic libraries in an E. coli host. We exposed cells containing the library to pinene, selecting for genes that improved tolerance. Importantly, we found that expressing the sigma factor RpoD from P. putida greatly expanded the diversity of tolerance genes recovered. With low expression of rpoDP. putida, we isolated a single pinene tolerance gene; with increased expression of the sigma factor our selection experiments returned multiple distinct tolerance mechanisms, including some that have been previously documented and also new mechanisms. Interestingly, high levels of rpoDP. putida induction resulted in decreased diversity. We found that the tolerance levels provided by some genes are highly sensitive to the level of induction of rpoDP. putida, while others provide tolerance across a wide range of rpoDP. putida levels. This method for unlocking diversity in tolerance screening using heterologous sigma factor expression was applicable to both plasmid and fosmid-based transgenic libraries. These results suggest that by controlling the expression of appropriate heterologous sigma factors, we can greatly increase the searchable genomic space within transgenic libraries. This dissertation describes a method of effectively screening genomic DNA from multiple organisms for genes to mitigate biofuel stress and shows how tolerance genes can improve bacterial growth in the presence of toxic biofuel compounds. These identified genes can be targeted in future studies as candidates for use in biofuel production strains to increase biofuel yields.

Biofuels have been identified as one of several GHG emission strategies to reduce the use of fossil fuels in the transport sector. Fast pyrolysis of biomass is one approach to producing second generation biofuels. The bio-oil product of fast pyrolysis can be upgraded into essential gasoline and diesel range products with conventional refinery technologies. Thus, it is important to assess their techno- economic and environmental performance at an early stage prior to commercialisation. This research was conducted with the goal of evaluating and comparing the techno-economic and environmental viability of the production of biofuels from fast pyrolysis of biomass and upgrading of bio-oil via two refinery technologies, viz. hydroprocessing and zeolite cracking. In order to achieve this aim, process models of fast pyrolysis of biomass and bio-oil upgrading via hydroprocessing and zeolite cracking were developed. The fast pyrolysis model was based on multi-step kinetic models. In addition, lumped kinetic models of the hydrodeoxygenation reactions of bio-oil were implemented. The models were verified against experimental measurements with good prediction and formed the foundation for the development of a 72 t/day fast pyrolysis plant model in Aspen Plus®. Several strategies were proposed for the two pathways to enhance energy efficiency and profitability. All in all, the results revealed that the hydroprocessing route is 16% more efficient than the zeolite cracking pathway. Moreover, the hydroprocessing route resulted in a minimum fuel selling price of 15% lower than that from the zeolite cracking pathway. Sensitivity analysis revealed that the techno-economic and environmental performance of the both pathways depends on several process, economic and environmental parameters. In particular, biofuel yield, operating cost and income tax were identified as the most sensitive techno-economic parameters, while changes in nitrogen feed gas to the pyrolysis reactor and fuel yield had the most environmental impact. It was concluded that hydroprocessing is a more suitable upgrading pathway than zeolite cracking in terms of economic viability, energy efficiency, and GHG emissions per energy content of fuel produced.

Philosophiae Doctor - PhD / The production of biodiesel (methyl esters) from vegetable oils represents analternative means of producing liquid fuels from biomass, and one which is growing rapidly in commercial importance and relevance due to increase in petroleum prices and the environmental advantages the process offers. Commercially, biodiesel is produced from vegetable oils, as well as from waste cooking oils and animal fats. These oils are typically composed of C14-C20 fatty acid triglycerides. In order to produce a fuel that is suitable for use in diesel engines, these triglycerides are usually converted into the respective mono alkyl esters by base-catalyzed transesterification with short chain alcohol, usually methanol. In the first part of this study, the transesterification reactions of three different vegetable oils; sunflower (SFO), soybean (SBO) and waste cooking oil (WCO) with methanol was studied using potassium hydroxide as catalyst in a conventional batch process. The production of biodiesel from waste cooking oil was also studied via continuous operation systems (employing the use of low frequency ultrasonic technology and the jet loop reactor). The characterisation of the feedstock used and the methyl ester products were determined by different analytical techniques such as gas chromatography (GC), high performance liquid chromatography (HPLC) and thin layer chromatography (TLC). The effects of different reaction parameters (catalyst amount, methanol to oil ratio, reaction temperature, reaction time) on methyl ester/FAME yield were studied and the optimum reaction conditions of the different process systems were determined. The optimum reaction conditions for production of methyl esters via the batch process with the fresh oil samples (SFO and SBO) were established as follows: a reaction time of 60 min at 60 ºC with a methanol: oil ratio of 6:1 and 1.0 KOH % wt/wt of oil; while the optimum reaction conditions for the used oil (WCO) was observed at a reaction time of 90 min at 60 ºC, methanol: oil ratio of 6:1 and 1.5% KOH wt/wt of oil. The optimum reaction conditions for the transesterification of the WCO via ultrasound technology applied in a continuous system in this study were: a reaction time of 30 min, 30 ºC, 6:1 methanol/oil ratio and a 0.75 wt% (KOH) catalyst concentration. The ultrasound assisted transesterification reactions performed at optimum conditions on the different oil samples led to higher yields of methyl esters (96.8, 98.32 and 97.65 % for WCO, SFO and SBO respectively) compared to methyl esters yields (90, 95 and 96 % for WCO, SFO and SBO respectively) obtained when using conventional batch procedures. A considerable increase in yields of the methyl esters in the ultrasound assisted reaction process were obtained at room temperature, in a remarkably short time span (completed in 30 min) and with a lower amount of catalyst (0.75 wt % KOH) while the results from the continuous jet loop process system showed even better results, at an optimum reaction condition of 25 min of reaction, a methanol: oil ratio of 4:1 and a catalyst amount of 0.5 wt%. This new jet loop process allowed an added advantage of intense agitation for an efficient separation and adequate purification of the methyl esters phase at a reduced time of 30 min. The use of homogeneous catalysts in conventional processes poses many disadvantages; heterogeneous catalysts on the other hand are attractive on the basis that their use could enable the biodiesel production to be more readily performed as a continuous process resulting in low production costs. Consequently, a solid base catalyst (KNO3/FA) prepared from fly ash (obtained from Arnot coal power station, South Africa) and a new zeolite, FA/Na-X synthesized from the same fly ash were used as solid base catalysts in the transesterification reactions in the conversion of a variety of oil feedstock with methanol to methyl esters. Since fly ash is a waste product generated from the combustion of coal for power generation, its utilization in this manner would allow for its beneficiation (as a catalytic support material and raw material for zeolite synthesis) in an environmentally friendly way aimed at making the transesterification process reasonably viable. Arnot fly ash (AFA) was loaded with potassium (using potassium nitrate as precursor) via a wet impregnation method while the synthesized zeolite FA/Na-X was ion exchanged with potassium (using potassium acetate as precursor) to obtain the KNO3/FA and FA/K-X catalysts respectively. Several analytical techniques were applied for characterization purposes. The results of the XRD and XRF showed that the AFA predominantly contained some mineral phases such as quartz, mullite, calcite and lime. The high concentration of CaO in AFA was apparent to be beneficial for the use of fresh fly ash as a support material in the heterogeneous catalysed transesterification reactions. XRD characterisation of KNO3/FA results indicated that the structure of KNO3/FA gradually changed with the increase in KNO3 loading. The catalyst function was retained until the loading of KNO3 was over 10 %. IR spectra showed that the KNO3 was decomposed to K2O on the fly ash support during preparation at a calcination temperature of 500 ºC. The CO2-TPD of the KNO3/FA catalysts showed that two basic catalytic sites were generated which were responsible for high catalytic abilities observed in the transesterification reactions of sunflower oil to methyl esters. On the other hand, XRD results for the as- received zeolite synthesized from AFA showed typical diffraction peaks of zeolite NaX. SEM images of the FA /NaX showed nano platelets unique morphology different from well known pyramidal octahedral shaped crystal formation of faujasite zeolites and the morphology of the FA /KX zeolite did not show any significant difference after ion exchange. The fly ash derived zeolite NaX (FA /NaX) exhibited a high surface area of 320 m2/g. The application of the KNO3/FA catalysts in the conversion reactions to produce methyl esters (biodiesel) via transesterification reactions revealed methyl ester yield of 87.5 % with 10 wt% KNO3 at optimum reaction conditions of methanol: oil ratio of 15:1, 5 h reaction time, catalyst amount of 15 g and reaction temperature 160 °C, while with the use of the zeolite FA/K-X catalyst, a FAME yield of 83.53 % was obtained for 8 h using the ion exchanged Arnot fly ash zeolite NaX catalyst (FA/KX) at reaction conditions of methanol: oil ratio of 6:1, catalyst amount of 3 % wt/wt of oil and reaction temperature of 65 ºC. Several studies have been carried out on the production of biodiesel using different heterogeneous catalysts but this study has been able to uniquely demonstrate the utilization of South African Class F AFA both as a catalyst support and as a raw material for zeolite synthesis; these catalyst materials subsequently applied sucessfully as solid base catalysts in the production of biodiesel. / South Africa

Les biopiles microbiennes (PACB) sont un type de pile à combustible utilisant des bactéries comme catalyseurs. Par la métabolisation de matières organiques, les bactéries produisent et transfèrent des électrons à une matrice conductrice. Les matériaux carbonés, comme les feutres de carbone (fibres de 10 µm de diamètre) sont adaptés comme matériau anodique. L’objectif de cette thèse est d’évaluer l’effet des paramètres expérimentaux et structuraux sur la formation du biofilm et sur le comportement électrochimique d’une bactérie électro-active à la surface d’une électrode. Suite à l’optimisation de la croissance de Shewanella oneidensis en condition de semi-aérobie, l’effet de la présence d’oxygène, de l’état de croissance de la bactérie et de la nature de l’électrolyte sur le transfert électronique, ont été évalué. La polarisation de l’anode a des potentiels compris entre -0.3 et 0.5 V conduit à deux conclusions : (i) Les bactéries sont plus sensibles a des potentiels positifs élevés en réacteur mono-compartiment. (ii) En PACB à deux compartiments, les potentiels négatifs et positifs conduisent à deux structures de biofilm différentes. Un biofilm artificiel a été conçu en encapsulant des bactéries dans une gel de silice incorporé dans un feutre de carbone. Il apparait que le transfert électronique des bactéries encapsulées varie en fonction de la rigidité du réseau de silice. Finalement, par l’electrospinning d’une solution de PAN et le traitement thermique de la membrane obtenue, une électrode formée de fibres micrométriques a été conçue. Son utilisation en PACB conduit à une augmentation des performances de la biopile. Le courant anodique augmente d’un facteur 10 à 100. / Microbial fuel cells (MFC) are a type of fuel cells based on bacteria as biologic catalysts. By the metabolism of organic compounds, these micro-organisms produce and transfer electrons to a conductive matrix. The objective of this study is to evaluate the impact of working conditions and structural parameters on the biofilm formation and the electrochemical behaviour of electroactive bacteria. By optimising the bacterial growth of Shewanella oneidensis strain in semi-aerobic condition, various working condition was evaluated to better understand the interaction between a carbon felt (CF) electrode and the bacteria. It appears that the bacterial state of growth influences the electron transfer of the cells, as well as the electrolyte nature. The effect of the anodic polarization was evaluated by applying various poised potential between -0.3 V and 0.5 V in both single and dual-chamber MFC. This study leads to the conclusion that bacteria are more sensible to highly positive potential in membrane-less MFC. On the contrary, in dual-chamber reactors, both positive and negative potential leads to the formation of different biofilm architectures. Then, an artificial biofilm was created by incorporating bacteria encapsulated into a silica gel into a CF. The electrochemical behaviour of bacteria seems sensible to the tightness of the silica network. Finally, by the electrospinning of polyacrylonitrile solution and then the annealing of the fiber mat, an electrode with micro-scaled carbon fibers was produced. The use of this electrode as an anode in a MFC leads to an increase of the MFC performance and more specially of the anodic current density by a factor 10 to 100.

Miniaturized, self-sufficient bioelectronics powered by unconventional micropower may lead to a new generation of implantable, wireless, minimally invasive medical devices, such as pacemakers, defibrillators, drug-delivering pumps, sensor transmitters, and neurostimulators. Studies have shown that micro-enzymatic biofuel cells (EBFCs) are among the most intuitive candidates for in vivo micropower. In the fisrt part of this thesis, the prototype design of an EBFC chip, having 3D intedigitated microelectrode arrays was proposed to obtain an optimum design of 3D microelectrode arrays for carbon microelectromechanical systems (C-MEMS) based EBFCs. A detailed modeling solving partial differential equations (PDEs) by finite element techniques has been developed on the effect of 1) dimensions of microelectrodes, 2) spatial arrangement of 3D microelectrode arrays, 3) geometry of microelectrode on the EBFC performance based on COMSOL Multiphysics. In the second part of this thesis, in order to investigate the performance of an EBFC, behavior of an EBFC chip performance inside an artery has been studied. COMSOL Multiphysics software has also been applied to analyze mass transport for different orientations of an EBFC chip inside a blood artery. Two orientations: horizontal position (HP) and vertical position (VP) have been analyzed. The third part of this thesis has been focused on experimental work towards high performance EBFC. This work has integrated graphene/enzyme onto three-dimensional (3D) micropillar arrays in order to obtain efficient enzyme immobilization, enhanced enzyme loading and facilitate direct electron transfer. The developed 3D graphene/enzyme network based EBFC generated a maximum power density of 136.3 μWcm-2 at 0.59 V, which is almost 7 times of the maximum power density of the bare 3D carbon micropillar arrays based EBFC. To further improve the EBFC performance, reduced graphene oxide (rGO)/carbon nanotubes (CNTs) has been integrated onto 3D mciropillar arrays to further increase EBFC performance in the fourth part of this thesisThe developed rGO/CNTs based EBFC generated twice the maximum power density of rGO based EBFC. Through a comparison of experimental and theoretical results, the cell performance efficiency is noted to be 67%.

The aim of this study is to identify characteristics that can be used to assess early-stage research results by research users and research producers of the advanced biofuel sector. Mainly, it qualitatively explores the perceptions of both research users and research producers regarding their experiences with research results. The study builds on the models of Diffusion of Innovation (DoI), Technology Acceptance Model (TAM) and Perceived Characteristics of Innovation (PCI). The findings of this study suggest that the investigated dimensions of DoI, PCI and TAM are applicable to the context of assessing research results with the extra dimension of risk reduction. In particular, some of the criteria used to assess the usefulness of research results are through its originality, scalability and relevance. The findings also suggest that documentation and publication are important to research users: Research users assess ease of use based on the presentation of the research results in their documentation; and they assess the quality of research results based on publications and the reputation of researchers. The findings of this study can be used to tailor research results to research users’ needs, which in turn can be expected to improve the uptake and further development of research results. This will not only permit the push of scientific research results to research users only put also permit research users to inform research needs.

Due to environmental challenges, depleting oil resources, rising cost of oil and instability in oil-producing countries, biofuel production has attracted a lot of attention in recent decades. Biobutanol is one of the biofuels showing the most potential as an alternative for partly replacing petroleum-based fuels. Both researchers and industrialists are currently working at developing an energy-effective process to produce biobutanol at a large scale. Acetone-butanol-ethanol (ABE) fermentation is the biological process of biobutanol production and Clostridia are the most common bacteria used to produce biobutanol. However, there are several challenges in the butanol bioproduction process that should be addressed to make this process economically viable. The main challenge in the biobutanol production process is the low concentration of butanol in the ABE fermentation broth. It is therefore important to develop an efficient separation method. Several separation methods such as distillation, liquid-liquid extraction (LLE), pervaporation, gas stripping and adsorption have been considered to recover butanol from dilute solutions and ABE fermentation broths. Adsorption is considered as one of the most promising methods due to its high performance and energy efficiency for butanol separation. In this study, the focus was on developing an efficient separation method for butanol recovery from dilute model solution and fermentation broth using adsorption. A comprehensive adsorbent screening was first carried out to identify the best commercially available adsorbent among a series of potentially promising adsorbents. Activated carbon (AC) F-400 was selected for further experimentation since it showed high adsorption capacity and adsorption rate in addition to high selectivity toward butanol. AC F-400 was then tested extensively in packed adsorption column experiments for binary and ABE model solutions and fermentation broths to investigate the competitive adsorption between butanol and other components present in ABE broths. The results showed that the butanol adsorption capacity was not affected by the presence of ethanol, glucose and xylose while the presence of acetone led to a slight decrease in adsorption capacity at low butanol concentrations. On the other hand, the presence of acids (acetic acid and butyric acid) in the ABE broth showed a significant effect on the butanol adsorption capacity over a wide ii range of butanol concentration and this effect was more pronounced for butyric acid. At the end, different competitive adsorption isotherm models were also studied to appropriately represent the behaviour of the competitive adsorption. Desorption of butanol was subsequently investigated to evaluate both the desorption capacity of butanol and the capability of the adsorbent particles to be used for multiple adsorption-desorption cycles. The results of this set of experiments showed that AC F-400 can retain its initial adsorption capacity after 6 adsorption/desorption cycles. The recovery of butanol from butanol-water (1.5 wt%) binary and ABE model solutions was 84 and 80% with butanol adsorption capacity of 302 and 171 mg/g, respectively. The combination of adsorption and gas stripping techniques was also studied to investigate the performance of CO2 gas stripping of solvents from the model solutions and fermentation broths followed by adsorption. The results showed that the butanol adsorption capacity of the overall system for binary solutions (260 mg/g for a binary butanol-water solution of 15 g/L with vapour phase concentration of 5.8 mg/L), ABE model solutions (192 mg/g for a corresponding vapour concentration of 5.2 mg/L) and ABE fermentation broths (247 mg/g for a corresponding vapour phase concentration of 2.5 mg/L) was higher than what has been published in the literature. Finally, a model was developed and adequately validated the experimental data to predict the behaviour of the ABE compounds in a packed bed adsorption column for butanol separation from dilute solutions.