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 object of this work was to study some of the biochemical effects of various oxygen-transfer conditions in submerged cultures of a facultative anaerobe, \(Klebsiella\) \(aerogenes\) N.C.I.B. 418. A well-mixed laboratory fermenter with extensive instrumentation was used to reproduce and monitor some possible effects of 'cyclic aeration', a phenomenon experienced by microorganisms in most industrial fermentations. Batch and continuous cultures were carried out both aerobically and anaerobically, using a synthetic glycerol-salts medium. 'Cyclic aeration' was simulated by 'intermittent aeration', air and nitrogen being supplied alternately to the fermenter over a five-minute cycle. The aerobic enzymes (glycerol kinase and glycerol-3-phosphate dehydrogenase) and anaerobic enzymes (glycerol dehydrogenase and dihydroxyacetone kinase) involved in the conversion of glycerol to dihydroxyacetone phosphate were assayed in each culture sample. An aerobic→anaerobic transition, indicated most noticeably by a marked reduction of cell density, was found to take place rather sharply as the aeration time per cycle was progressively reduced. The transition point and the sharpness of the transition were dependent on oxygen-transfer efficiency during the aeration period, as well as on the aeration time per cycle, and resulted in reductions in the levels of the aerobic enzymes and increases in the levels of the anaerobic enzymes. Specific carbon dioxide production increased as 'aeration condition' was reduced to the point of fully anaerobic growth; its measurement was used, together with that of culture dissolved oxygen tension, to follow the progress of the transition. It is suggested that the determination of the complement of these enzymes could be used to assess the effectiveness of oxygen distribution in industrial fermenters.

Probiotics are live microorganisms including yeast and bacteria used as food supplements to offer health benefits. Currently available forms of yeast probiotic products include powder and gelatine capsules. A new yeast probiotic product in tablet dosage form has been developed in order to prolong product shelf life and improve product stability. The aim of the present work was to study the physiological states of yeast cells in various formulation and conditions, and to develop a rigid tablet which contains the adequate number of active yeast cells. Yeast cells became injured and had lower culturability when they were exposed to a high shear force of homogenization and compaction pressure. Tablets containing freeze dried yeast resulted in low tensile strength and could not withstand handling. Encapsulation of yeast cells with pectin demonstrated better survival and showed desirable water activity. Furthermore, the material properties of calcium pectinate beads have been investigated. A compaction of CaP beads into tablets at 90 MPa created rigid tablets with the adequate number of viable cells. Overall, encapsulated cells in CaP beads were protected more from damage during compaction and show more resistance to stress during storage. The use of flow cytometry together with fluorescent dyes for the monitoring of cell physiological states has also been demonstrated.

There is an increasing demand from the pharmaceutical and food industries for new probiotic products. Some yeast strains offer probiotic benefits, but it has not been possible to formulate them successfully into a tablet dosage form. Direct compression is regarded as the best technique for producing tablets containing dried yeast, however, the main challenge of tabletting a powder mixture containing yeast granules is the mechanical sensitivity of the cells. The objective of this work was to develop a rigid yeast tablet containing adequate numbers of viable yeast cells by optimizing the formulation to allow a relatively low compaction force to be used. In addition the mechanical properties of primary particles and granules were determined as an attempt to predict the compaction behaviour during tabletting. A tablet formulation was developed which exhibited tablets of an acceptable tensile strength. These tablets were further tested for friability, dissolution and storage stability to ensure it is fit for consumer use.

This work presents a novel method of Sn-infiltration on SOFC anodes for SOFC operation in biogas dry reforming. Using commercially available NiYSZ-based anode supported half cells with hand-painted LSM/YSZ cathode layers, Sn-infiltrated NiYSZ SOFCs containing different amounts of Sn were manufactured. These SOFCs were tested for their electrochemical performance and quantity of deposited carbon during operation on simulated biogas of 1:2 volume ratio of CO2:CH4 without humidification but with 25% Helium added to the feed stream to enable measurements of the fuel cell outlet gas composition using a quadrupole mass spectrometer. Most of the SOFCs were tested in biogas for 1 day (22 hours), but several cells were tested for 6 days (150 hours) to evaluate performance degradation. The electrochemical performance tests at 750 oC showed that with H2 as fuel the non-infiltrated NiYSZ SOFCs were able to reliably generate a moderate level of current of 350 mA cm-2 at 0.7 V; however when simulated biogas was introduced, current dropped significantly to 90-200 mA cm-2. Contrary to non-infiltrated cells, a series of Sn-infiltrated cells under the same operating conditions performed equally well both on H2 and biogas producing 310 to 420 mA cm-2 at 0.7 V. Several cells showed stable electrochemical performance over 150 hours of operation both on H2 and biogas. Using Temperature Programmed Oxidation (TPO), both Sn-infiltrated and non-infiltrated SOFCs showed low quantities of carbon formed during 22 hours operation on biogas. Visual observation and SEM images of the anode surface after 150 hours operation on biogas showed no sign of deposited carbon. The conclusion is that Sn-infiltrated NiYSZ-based SOFC can be operated on simulated biogas with significantly higher electrochemical performance and low carbon deposition, given the anode is adequately modified.

Surface engineered systems for industrial applications must be able to withstand the harsh inservice environments that they will be operated under. Localised testing on the nanoscale is a method commonly used to probe such systems at very high temperatures, varying humidity and even under liquid environments. However little or no research has been directed towards investigating their behaviour under low temperature conditions. In this study a novel sub-ambient temperature nanomechanical testing instrument has been designed and developed. It allows testing of materials under the temperature range from 20 oC to minus 30 oC. The instrument employs peltier coolers to provide vibration free measurements and a custom purging chamber has been designed to prevent condensation of water vapour on the sample surface during the sub-ambient testing. The study demonstrated the need for dual cooling of both the sample and indenter to ensure drift free measurements are obtained under sub-ambient regimes. A section of the research is dedicated to the testing of polymeric materials. A range of tests were performed from nanoindentation through to probing of time and environmental dependence parameters. In particular creep was studied at ambient temperatures on a range of engineering polymers and also on Nylon’s which were submerged in a fluid cell. The prototype was constructed and validation tests carried out to ensure its performance on standard samples. Next the mechanical properties and creep behaviour of an atacticpolypropylene through its glass transition temperature was examined. Further experiments were carried out focusing on tribological testing of surface engineered systems with the new prototype providing interesting results on DLC’s when tested under below ambient temperatures. Based on the outcomes of this research, a few papers have been published in peer-reviewed technical journals and it is envisaged that the novel sub-ambient instrumentation will be used for the design, charaterisation and optimization of novel engineered surfaces for various environmental applications.

This thesis took a unique multidisciplinary approach, combining understanding of food engineering, sensory science, nutrition and psychology, to investigate how emulsion-based food products can be made more satiating whilst maintaining or improving the products sensory and hedonic qualities. To achieve this, model oil-in-water emulsion systems were designed. Oil droplet size (0.1 µm – 50µm) was the main microstructural variable investigated. The influence of oil droplet size upon viscosity, friction, sensory perception, hedonics and expected and actual food intake behaviour was investigated. The main finding of the work highlighted oil droplet size significantly affects hedonics, expected and actual food intake behaviour and the perception of numerous sensory attributes. It was shown Creaminess was a strong hedonic indicator, but interestingly it also showed to significantly induce greater expectations of satiety and satiation. Structurally, Creaminess significantly increased with decreasing oil droplet size. Through a preload study, expectations were shown to be reflected in actual food intake behaviour, with smaller droplets resulting in a significant 12% reduction of food intake. Sensory results, indicated that the mechanism in which oil droplet size modified Creaminess was through altered texture and mouthfeel. Instrumental characterisation of the emulsions highlighted that this was a result of a combined influence of viscosity and droplet behaviour during oral processing, the sensory interpretation of these two physical variables being Thickness and Smoothness, reflecting Kokini’s Creaminess predication equation. Throughout this thesis the potential of emulsion structure on synergistically increasing both the satiety and hedonics of emulsion based foods was realised.

Efficacy of subcritical water in the recovery of the polyphenolic compounds from the apple pomace using a batch reactor system at 100-bar over a temperature range of 100-200oC for a residence time of 10–30 minutes was investigated. Organic solvent extractions using acetone and ethanol were carried out to serve as a baseline for comparison with the subcritical water extraction. Subcritical water was efficient in solubilising the apple pomace, and extracting polyphenolics with high antioxidant activity. Maximum solubilisation of the apple pomace was achieved at 145oC for 30 minutes and total phenolic content and antioxidant activity at 200oC. Solubilisation, ORAC activity and total phenolic content of subcritical water extract were 28.20g/100g DW, 99285μmol TE/g DW and 49.86mg/g GAE DW of apple pomace respectively, compared to 19.20g/100g DW, 6260.27 μmol TE/g DW and 21.70mg/g GAE DW of acetone extracts of apple pomace respectively. Protocatechuic aldehyde was identified for the first time only in the subcritical water extract and to date has not been identified in solvent extracts of cider apple pomace. Encapsulation of polyphenolic s of subcritical water extract using spray drying was explored. Particles/powders formed were derived from the naturally occurring carbohydrate polymers co-extracted with polyphenols. Addition of HPβ-Cyclodextrins (SWE+ HPβ-CD) to the directly encapsulated powder (SWE) significantly reduced hygroscopicity and improved antioxidant activity.

This research shows, for the first time, the freeze dried low acyl (LA) gellan gum, high acyl (HA) and HA:LA mixture gel structures and their properties upon rehydration. The water interaction with the gel structure is affected by the presence of acyl groups along the HA gellan gum polymer chain. The rehydration rate was shown to be lower for HA gellan gum and was not dependent on the polymer concentration. In the second instance, the effect of the gel pH on the freeze- and oven-dried structure is studied as well as the water re-absorption extent and rate. In this part, two drying methods, freeze- and oven-drying, were performed. Finally, a comparison of the three drying processes (freeze-, oven- and supercritical-fluid drying) is reported, proposing the effect on the molecular structure by investigation of the disordered chain domains of the gel network. As supercritical-fluid drying requires a pre-treatment in alcohol, its effect on the gellan gum network was investigated. It is shown how alcohols change the gellan gum configuration, leading to a considerable variation in gel texture. A novel supercritical-fluid batch rig is also proposed, characterised by high process flexibility and reduced set-up and energetic costs, particularly suitable for small/laboratory-scale use.

Many biological and non-biological materials in the form of microscopic particles (or microparticles) are used to produce functional products for a wide range of industrial sectors including pharmaceutical and medical, chemical, agrochemical, food and feed, personal and household care. Understanding their mechanical properties is essential for predicting their behaviour in manufacturing and processing, and for maximising their performance in end-use applications. However, it had not been possible to determine the mechanical properties of single microparticles until the author, as the main contributor, developed a novel micromanipulation technique at the University of Birmingham. The technique is capable of determining the mechanical properties of both biological and non-biological particles as small as 400 nm in diameter, and can be used for obtaining force-displacement data of single microparticles at large deformations, including those corresponding to rupture. The technique was enhanced by mathematical modelling and finite element analysis in order to allow intrinsic material properties to be determined, for example, the particle (or particle wall) elastic modulus, viscoelastic and plastic properties, and stress/strain at rupture. For biological materials, applications of this technique include understanding mechanical damage to animal cells in suspension cultures, yeast and bacterial disruption in downstream processing equipment, biomechanics of chondrocytes and chondrons for tissue engineering, and adhesion and cohesion of biofilms and food fouling deposits. For non-biological materials, applications include understanding and controlling particle breakage in processing equipment, and the formulation of microcapsules with optimum mechanical strength to achieve controlled release and targeted delivery of functional active ingredients. The research on micromanipulation has been sponsored by BBSRC, EPSRC, DEFRA, DTI, EU, the Royal Society K C Wong Fellowships and 19 national and international companies, and has resulted in more than one hundred academic publications. The knowledge generated has also assisted these companies to commercialise particulate functional products.