This thesis investigates both experimentally and numerically the oxidation, sintering, melting and solidification processes of different nanoparticles under various thermodynamic scenarios, with a background for energy applications. Two sets of main techniques are adopted in this work, which are isoconvensional kinetic analysis and molecular dynamics simulation. Based on the techniques of simultaneous Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC), for first time the isoconvensional kinetic analysis is applied to study the oxidation of nickel and tin nanoparticles. This method is demonstrated capable of modelling one-step nanoscale oxidation and revealing underling kinetic mechanisms. Moreover, some distinct features of nanoparticle oxidation compared with their bulk counterparts are found such as melting depression, oxidation kinetic change in the vicinity of Curie point of nickel and pressure-related two-step oxidation of tin nanoparticles. The detailed study from Molecular Dynamics (MD) simulation establishes a three-stage sintering process of two nickel nanoparticles, which is unable to be described by bulk continuum-level models. MD is applied to study the interaction between nickel and aluminium and its consequent thermo-mechanical and structural property evolution in a nickel-coating aluminium particle in a heating and cooling cycle. The simulation successfully predicts the atomic diffusion during melting and the formation of glass and crystal phases, and allows for the estimation of interior core-shell pressure. Reactive MD is then applied to simulate the oxidation of silicon nanoparticles. It predicts well the exothermal reaction process and experimentally reveals the oxygen exchange process.

Energy is an important requirement for population growth, technological progress and urbanisation. Worldwide energy demand has been projected to increase by 5-fold by 2100. Fulfilment of these energy requirements cannot be solely from fossil fuels, such as oil, coal and natural gas, on account of their adverse environmental impacts and concomitant depletion of natural resources. As a result multiple approaches for generating alternative energy are being explored globally. In this study, processed municipal solid waste (MSW) fibre was assessed as a substrate for the production of various bio-energy related products. The MSW was characterised and the results showed that there was, as expected, a wide compositional variation between samples. There was a significant amount of lignocellulosic material found in some samples and the potential to exploit this to generate fermentable sugars was explored. Direct enzyme hydrolysis using 30 FPU (Filter Paper Units)/g Cellic® CTec2 gave a 30 % release of available glucose. Pre-treatments- using hot water, dilute acid and dilute alkali are all applied to enhance sugar release but were all found to be ineffective. The possibility of using MSW as a substrate for cellulase enzyme production via solid state fermentation (SSF) by Trichoderma reesei (T. reesei) and Aspergillus niger (A. niger) was explored. Both fungi grew well on the substrate and following optimization a cellulase activity of 26.10±3.09 FPU/g could be produced using T. reesei at 30 °C with a moisture content of 60 % with inoculation of 0.5 million spores/g and incubation for 168 hr. Addition of extra nitrogen and/or carbon did not improve cellulase accumulation. Acid or alkali pre-treatment of MSW led to reduced cellulase production. Crude enzymes produced from MSW by T. reesei were evaluated for their ability to release glucose from MSW. A cellulose hydrolysis yield of cellulase was 24.7 % achieved, which was close to that obtained using a commercial enzyme. Results demonstrated that MSW could be used as an inexpensive lignocellulosic material for the production of cellulase enzymes. High concentrations of toxic heavy metals were found in all MSW samples tested and this precludes the use of this material as a soil enhancer. Thus studies were undertaken to explore the potential for bioleaching as a means to generate compost that meets environmental standards for safe use. A. niger and Saccharomyces cerevisiae NCYC2592 were used and the impact of growth medium and pH tested. Both organisms were effective at solubilising the heavy metals and this may be related to their ability to synthesise organic acids into the fermentation medium that act as chelators.

Functional food ingredients such as prebiotics are emerging as effective tools for managing the risks associated with gastrointestinal diseases and gut related dysfunctions. This work explores the production of prebiotic rich extracts from two sources of lignocellulosic biomass – energy crop \(Miscanthus\) \(χ\) \(giganteus\), and oat (\(Avena\) \(sativa\)) husks, an agricultural by-product. Whilst most of the research to date has been focusing on the utility of cellulose, the hemicellulose and lignin fractions have been underutilised. This work expands the value of the hemicellulose fraction by extracting the prebiotic xylo-oligosaccharides (XOS) and other hemicellulose derived products using environmentally benign sub-critical water in a 0.5 L stirred batch reactor at temperatures between 120-220°C with residence times 0-77 min, and 0.5-13% (w/v) biomass loading. The extracts were analysed with HPAEC-PAD, HPLC and colorimetric assays. Almost complete hemicellulose solubilisation was achieved, and highest yields of prebiotic (DP 2-5) XOS were observed at 170°C and 35-77 min corresponding to 44-56% with little amounts of carbohydrate degradation products and low total phenolic contents. Although higher yields were achieved with oat husks, the XOS extractability was comparable between the biomass sources. Higher extraction severities resulted in further XOS depolymerisation into monosaccharides and eventual formation of furfural and 5-HMF.

The interaction between MgH2 and LiBH4 was studied to determine the resultant effects on hydrogen desorption and absorption kinetics for potential use as a hydrogen storage material. It is found that the addition of LiBH4 in small molar ratios results in improved kinetics of the same order as those observed for mechanically milled magnesium. The mixture of MgH2 + LiBH4 in ratios at and below 4:1, once reacted, is a highly reversible material at 300°C and it is observed that the kinetics improve upon the process of hydrogen cycling. This improvement is partially attributed to a refinement in microstructure that results in highly porous particle agglomerates and it is this feature that is likely to have a large effect on the kinetics of hydrogenation due to the rate limiting step of the reaction being hydrogen diffusion into the particles of Mg which can be coated in MgH2 phase, through which H2 does not diffuse easily. Additionally it is observed via Raman spectroscopy that a new bonding structure exists in the H2 cycled mixture after desorption which might improve the rehydrogenation of the sample and reduce the enthalpy of decomposition through an intermediate reaction pathway.

Algae have been studied as a potential biodiesel feedstock by identifying on a global scale suitable cultivation locations for three specific cases (EU, US and Brazil) based on the area requirements. A direct conversion of oil harvested from wet algae to biodiesel was undertaken using ethanol at supercritical conditions, eliminating the use of catalyst, feedstock drying and the oil extraction steps. Chlorella vulgaris with 7.3% wt. lipid content was characterised (by elemental, chemical and thermal analyses) and used to assess the supercritical ethanol approach. A biodiesel yield of 47.5% wt. was achieved in a flow reactor at 260°C, 75 bar, aqueous algae concentration of 6 mg·mL-1 and 2 mL·min-1 flowrate. This result demonstrates the advantages of the flow reactor over a batch process where the maximum biodiesel yield was 26% wt. after 6 hours. A life cycle analysis of the proposed route showed that biodiesel yield must exceed 60% wt. to make the process competitive when compared to the traditional route of oil extraction and catalyst transesterification adopted to algae biodiesel production. In comparison to the soybean biodiesel, the use of algae as feedstock would not be justified unless improvements to reduce energy consumption are made.

Solid state hydrogen storage materials have become a key area of research over the past 20 years. In this work, the potential of zeolites to occlude hydrogen storage materials as guests to make composite materials was explored. Lithium borohydride was successfully loaded in zeolites NaA, NaX and NaY; showing a two phased system. Desorption of hydrogen from the occluded lithium borohydride was 5\(^\circ\)C lower than that of bulk lithium borohydride, but with slower kinetics, implying diffusion effects of occlusion into the host. Adsorption showed reduced uptakes of hydrogen at 77 K compared with the host zeolite, which was consistent with the degree of loading. Limited hydrogenation was achieved with milder conditions at 350\(^\circ\)C at 15 bar hydrogen of the desorbed lithium borohydride. Heats of adsorption were estimated for the samples both before and after high temperature desorption of hydrogen. Lithium borohydride was also loaded into zeolitic carbons and lithium, copper (II) and ammonium ion-exchanged zeolites. Copper exchanged zeolite catalysed desorption of hydrogen from lithium borohydride was most promising and occurred at room temperature. Lithium and ammonium exchanged zeolite showed a 10\(^\circ\)C reduction in desorption temperature, the ammonium system showing the best diffusion kinetics, with a sharp desorption similar to the bulk lithium borohydride. NaA and NaX were occluded with ammonia borane and lithium borohydride amide [Li\(_4\)BH\(_4\)(NH\(_2\))\(_3\)]. NaY containing occluded sodium was found to hydrogenate at room temperature at pressures up to 15 bar. This was accompanied with trapping of hydrogen and an increased adsorption of hydrogen at low temperature, exceeding the gravimetric absorption value for zeolite NaY.

Fuel cells could substantially decarbonise domestic energy production, but at what cost? It is known that these micro-CHP systems are expensive but actual price data has been elusive. Economic realities constrain individuals’ decisions to purchase and national policies on climate change, so this lack of understanding has delayed commercialisation and government support. Models were therefore developed to simulate the economic and environmental benefits from operating fuel cell micro-CHP systems in UK homes, and to project current purchase prices into the near future. These models were supplied with economic and performance data from an extensive meta-review of academic and commercial demonstrations; showing for example that fuel cell efficiencies are a third lower when operated in people’s homes rather than in the laboratory. These data inputs were combined with energy consumption data from 259 houses to give a broad definition of operating conditions in the UK. The techno-economic fuel cell simulation model was validated against results from literature and Japanese field trials, and then used to estimate the changes in home energy consumption from operating the four leading fuel cell technologies in the UK. Fuel cells are shown to offer negligible financial benefits in the UK at present. Energy bills would increase in 30-60% of homes, due in part to the low value of exported electricity. Savings are higher in houses with larger energy bills, but significant variation between similar properties confirms that simple trends cannot be used to identify ideal houses for fuel cell micro-CHP. The feed-in tariff proposed by the UK government would radically improve economic outcomes; as 10p paid per kWh of electricity generation would reward fuel cell owners with £600-750 annually. It is estimated that today’s fuel cells produce 360-450g of CO\(_2\) per kWh of electricity generated due to reforming natural gas into hydrogen on-site. Their carbon intensity is therefore 30-45% lower than the UK grid, enabling average annual emissions reductions of 1-2.2 tonnes per home. These reductions depend strongly on the displaced electricity generation method, and could therefore range from around zero when displacing high efficiency gas turbines up to 5.5 tonnes if displacing coal. From learning-by-doing, the price of Japanese 1kW PEMFC systems is shown to have fallen by 19.1-21.4% for each doubling of production volume. Prices are therefore projected to fall from £15,000 today to £6,000 within 10±5 years, determined primarily by the speed and scale of deployment world-wide. A commercially viable price of around £3,000 is however expected to be two decades away, and widely held targets of under £1,000 per kW are argued to be unobtainable with current technologies due to the requirement for extensive balance of plant and auxiliary systems. Combining all these findings, the payback period of PEMFC systems would be 25-45 years with the proposed 10p/kWh feed-in tariff. This could fall to within current system lifetimes after 5-10 years of cost reductions; however, without this level of government support the savings from operation will be unable to give payback without major improvements in technology performance or more favourable energy prices. The carbon cost of current PEMFC systems is estimated at £750-950 per tonne of CO\(_2\) mitigated. This figure is highly sensitive to the carbon intensity of displaced generation, and would reduce to £175/T if generation from coal plants is avoided. Fuel cells are therefore not among the ‘low hanging fruit’ of carbon abatement technologies, although the carbon costs will halve over the next ten years in line with system price reductions. Investment in this technology must therefore be considered a long term strategy for low-carbon energy production.

The first examples of a new class of mixed anion complex hydride have been synthesised and characterised. The structures of three amide-borohydride complex hydrides of lithium and sodium, Li\(_4\)BH\(_4\)(NH\(_2\))\(_3\), Li\(_2\)BH\(_4\)NH\(_2\) and Na\(_2\)BH\(_4\)NH\(_2\), have been solved by powder diffraction methods and characterised by infrared and Raman spectroscopy. The thermal decomposition of these hydrogen rich materials was investigated and hydrogen was observed as the major gaseous product in all cases. Ammonia was observed as a minor product with the amount of ammonia release dependent on the sample composition and experimental set-up. Powder diffraction was used to identify the solid decomposition products and decomposition pathways are proposed. Two competing decomposition pathways, one forming metal hydride and boron nitride, the other forming metal nitridoborate, were identified for the lithium system and suggested for the sodium system. \(In\)-\(situ\) and \(ex\)-\(situ\) powder diffraction, differential scanning calorimetry and temperature programmed desorption were used to investigate the lithium amide-borohydride system in detail and a phase diagram was proposed. The reactions of metal hydrides with Li\(_4\)BH\(_4\)(NH\(_2\))\(_3\) were tested and were found to reduce the amount of ammonia released. A reversible hydrogen storage reaction was observed upon reaction with magnesium hydride, which was investigated with gravimetric methods and \(ex\)-\(situ\) powder diffraction to elucidate the reaction pathway.

This study focuses on the utilization of solid carbonaceous wastes, the mitigation of CO2 and the development of CO2-based chemical production process which is divided into three main parts. The first part consists of the investigation of solid carbonaceous samples behaviours under pyrolysis and combustion processes. The second part covers experimental study of CO2 gasification aiming at the identification of interactions during co-gasification. Here, the presence of interactions will be further discussed, particularly in terms of increasing the gasification rate of low reactive carbonaceous sample and the effect of pyrolysis heating methods on gasification reactivity. The last part considers the thermodynamic assessment of conventional and CO2-enhanced biomass gasification. The objective is to identify the influence of CO2 as a gasifying agent in biomass gasification. Moreover, the comparisons study of bio-DME production based on conventional and CO2-enhanced gasification was also carried out in this thesis. (i) Pyrolysis of NMPCBS and combustion of solid carbonaceous materials This part consists of investigation of solid carbonaceous samples behaviours under pyrolysis and combustion processes. The objective is to explore the feasibility of the utilization of non-metallic part of waste printed circuit boards (NMPCB), including the thermal behaviours of NMPCB and its blends with two types of coals by using a thermogravimetric analyser (TGA). For individual sample, the results showed that the NMPCB had the fastest rate of pyrolysis and the highest maximum weight loss rate compared with coals, thus, the highest reactivity. These were attributed to the thermal degradation properties of the constituent elements in NMPCB. Meanwhile, based on kinetic study, it is evident that the lower heating rates favoured the pyrolysis process. For blends, it was revealed that there was 6%-7% deviation in terms of the yield of solid residue between experimental and calculated values, indicating a significant gap between the overall activation energy (Ea) of the blends and its average (Eave). Thus, it confirmed the existence of interactions in co-pyrolysis. Moreover, the combustion characteristics of an Australian coal, a suite of solid carbonaceous materials, and their blends were also investigated. A drop in both ignition temperature and burnout temperature was observed when carbonaceous wastes were blended with coal at different proportions (10 wt% and 30 wt%) which justified that there were strong interactions during the co-processing of coal with carbonaceous materials. The ignition index values of coal/polystyrene and coal/oat straw blends increased by 78% and 52%, respectively, when the blending ratio increased from 10 wt% to 30 wt%. Similarly, 2.6 times increase in combustion index was also observed in coal/oat straw blend. The presence of interactions in blends was further measured by using the root mean square interaction index (RMSII) which showed that coal/oat straw and coal/polystyrene blends had the highest RMSII values. This indicated the presence of strong interactions during co-combustion. (ii) CO2 gasification of solid carbonaceous materials The second part covers the feasibility evaluation of using CO2 as a gasifying agent, namely CO2 gasification, for various solid carbonaceous materials. The work includes the conversion of carbonaceous materials to syngas, gasification characteristics of coal, a set of waste carbonaceous materials, and their blends. The experiments were run by using a thermogravimetric analyser (TGA). The results showed that CO2 gasification of polystyrene completed at 470 °C, which was lower than those of other carbonaceous materials. This behaviour was attributed to the high volatile content coupled with its unique thermal degradation properties. Further results demonstrated that CO2 co-gasification process was enhanced as a direct consequence of interactions between coal and carbonaceous materials in the blends. The intensity and temperature of occurrence of these interactions were influenced by the chemical properties and composition of the carbonaceous materials in the blends. The strongest interactions were observed in coal/polystyrene blend at the devolatilisation stage, as indicated by the highest value of RMSII, whereas at char gasification stage, the highest interactions were found in coal/oat straw blend. The catalytic effect of alkali metals and other minerals in oat straw, such as CaO, K2O, and Fe2O3, contributed to these strong interactions, thus, the addition of polystyrene and oat straw enhanced the overall CO2 gasification of coal. On the other hand, interactions between petroleum coke and solid carbonaceous materials were also analysed with the aim of enhancing the gasification reactivity of highly unreactive petroleum coke. To achieve this, an Australian coal and gum wood were chosen for co-processing with petroleum coke. The addition of gum wood was found as the significant contributor of the enhanced gasification reactivity of petroleum coke. This is due to the combined influence of a number of unique features of bio-char, such as high surface area, more active sites, low crystalline index and the catalytic effect of alkali and alkaline earth metals (AAEM) compounds. These results confirmed that proper selection of solid carbonaceous materials for gasification of petroleum coke is an effective means to improve the conversion efficiency of petroleum coke, i.e., higher reactivity, and therefore expand its large scale utilization. In addition to coal and petroleum coke, the isothermal and non-isothermal CO2 gasification of an algal biomass (Chlorella) char were also carried out by using TGA under two different heating systems, i.e. conventional and microwave-assisted pyrolysis. Based on reactivity index, maximum peak temperature and maximum mass loss rate parameters, it was shown that microwave char had higher gasification reactivity than that of conventional char. Likewise, the activation energy value of microwave char also confirmed its higher reactivity which was found to be about 9.6% lower than that of conventional char. In addition, the physical properties of these chars, such as Brunauer-Emmett-Teller surface area, carbon crystalline structure and number of active sites, were systematically tested. Based on these properties, microwave char was found to be more reactive as demonstrated by its large BET surface area, low crystalline index and high active sites. Meanwhile, co-gasification experiments under isothermal condition revealed the existence of greater synergistic effects in coal char/microwave algae char blend than that present in coal char/conventional algae char blend. (iii) Process modelling and simulation The last part considers the process simulation of thermodynamic assessment for CO2-enhanced biomass gasification. The primary objective is to identify the influence of CO2 as a gasifying agent in biomass gasification. In this part, steam and CO2-enhanced gasification of rice straw was simulated using Aspen Plus simulator and compared in terms of energy, exergy and environmental impacts. It was found that the addition of CO2 had less impact on syngas yield than gasification temperature; the cold gas efficiency (CGE) increased with CO2/Biomass ratio. At lower ratios (below 0.25), gasification system efficiency (GSE) was below 22.1%, which is lower than that of conventional gasification. However, when CO2/Biomass ratio was increased, the GSE continued to increase and reached a peak of 58.8% at ratio of 0.87. In terms of syngas exergy, the value generally increases with CO2 addition mainly due to the increase in physical exergy. In this work, chemical exergy was found to be 2.05 to 4.85 times higher than physical exergy. The maximum exergy efficiency occurred within the temperature range of 800 oC to 900 oC, related to the peak of syngas exergy. For CO2-enhanced gasification, exergy efficiency was found to be more sensitive to temperature than CO2/Biomass ratios. In addition, the preliminary environmental analysis showed that CO2-enhanced gasification resulted in significant environmental benefits compared with stream gasification. However improved assessment methodologies are needed to better evaluate the advantages of CO2 utilization.

This thesis addresses the need for environmentally and socially responsible sources of energy. Biofuels, made from organic matter, have recently become a viable alternative to petroleum-based fossil fuel. Sugar and starch make up the majority of feedstock used in biofuel production as it is easily digested. However, the use of these feedstocks is problematic as they consume resources with negative implications. By using a bacterium able to utilise five and six carbon sugars, such as the thermophile Geobacillus thermoglucosidans, organic lignocellulosic waste material can be used as a feedstock. The aim of this project was to investigate and utilise key genetic regulators of fermentation in G. thermoglucosidans and to construct genetic engineering tools that enable strain development for second generation biofuel production. We have focused on the redox-sensing transcriptional regulator Rex, widespread in Grampositive bacteria, which controls the major fermentation pathways in response to changes in cellular NAD+/NADH ratio. Following the identification of several members of the Rex regulon via bioinformatics analysis, ChIP-seq and qRT-PCR experiments were performed to locate genome-wide binding sites and controlled genes in G. thermoglucosidans. Initial electromobility shift assay experiments were performed to demonstrate the potential for use of Rex from Clostridium thermocellum as an orthogonal regulator. To further this research, novel in vivo synthetic regulatory switches were designed and tested with the aim of controlling gene expression in response to changes in cellular redox state. In addition, new tools for the efficient genetic engineering of G. thermoglucosidans were produced and optimised, including an E. coli-G. thermoglucosidans conjugation method for plasmid transfer and gene disruption.