Renewable green alternatives to fossil fuels need to be sought in order to address the challenges of environmental and energy crises. Up until now, ethanol has been the major biofuel. Geobacillus thermoglucosidans is a thermophilic bacterium that is capable of producing bioethanol in an industrial setting at high temperatures and is capable of metabolizing pentoses and hexoses commonly found in lignocellulosic biomass. Due to these attractive properties, the aim of this work has been to construct a toolbox of genetic components to develop G. thermoglucosidans as as the leading thermophile chassis for synthetic biology and metabolic engineering. The toolbox is composed of shuttle vectors that have higher transformation efficiencies than previous existing vectors and are modular, where the presence of restriction sites separating each of the components allows users to exchange parts easily and efficiently. Also included in the toolbox are the fluorescent reporters sfGFP, mCherry and BsFbFP that will permit the characterization of promoters. As a proof-of-principle application to demontrate the effectivity of the toolbox for the production of valuable compounds, this work explores the production of isobutanol by the thermophile bacteria Geobacillus thermoglucosidans. Isobutanol is a higher chain alcohol that is a significantly better fuel molecule than ethanol, both for energy content and infrastructure compatibility. The Geobacillus host was able to produce isobutanol in amounts of around 50 mg/L via the conversion of isobutyryl-CoA to isobutyraldehyde by an (ALDH) and from isobutyraldehyde to isobutanol by an alcohol dehydrogenase (ADH). It was observed that supplementing the growth medium with an intermediate of the valine biosynthesis pathway, 2-ketoisovalerate, resulted in the production of isobutanol and overexpressing ALDH increased the isobutanol titres.

This thesis describes the design and engineering of a pressurised biomass gasification test facility. A detailed examination of the major elements within the plant has been undertaken in relation to specification of equipment, evaluation of options and final construction. The retrospective project assessment was developed from consideration of relevant literature and theoretical principles. The literature review includes a discussion on legislation and applicable design codes. From this analysis, each of the necessary equipment units was reviewed and important design decisions and procedures highlighted and explored. Particular emphasis was placed on examination of the stringent demands of the ASME VIII design codes. The inter-relationship of functional units was investigated and areas of deficiency, such as biomass feeders and gas cleaning, have been commented upon. Finally, plant costing was summarized in relation to the plant design and proposed experimental programme. The main conclusion drawn from the study is that pressurised gasification of biomass is far more difficult and expensive to support than atmospheric gasification. A number of recommendations have been made regarding future work in this area.

The study of buoyancy effects in enclosed jet systems is a much neglected field of combustion aerodynamics, research. Although theoretical analyses exist,little experimental data has been collected and this experimental investigation sets out to study the influence of various input momentum parameters on the deflection experienced by an enclosed buoyant jet. Due to the difficulty of modelling the jet under buoyant forces of sufficient magnitude,a technique has been used which was originally developed for free jet buoyancy studies. A slurry of finely ground Magnetite was used as a primary jet source whilst water was the fluid used for the general stream. Density ratios (Primary to secondary) of up to 2.7 have been used in the study whilst the velocity ratio was varied between 5 and 50, giving a range of Curtet numbers between 0.3 and 1.4. The resulting turbulent jet was photographed with a high speed 16mm. cine camera. From the film, measurements of jet enclosed angle, length of potential core, axial velocity and jet deflection were made. At the lower densities the jet angle was found to be constant for each density ratio, thus supporting the common assumption of constant entrainment rate, in jet systems where the variation in density of the jet fluid is small. However as the density ratio increased then it was found that the constant entrainment assumption was conditional on higher velocity ratios. Generally the assump tion only held for Curtet Numbers less than 0. 35. The axial velocity was found to decay significantly faster in the enclosed buoyant jet than predicted by the free jet theory. That this decay was a result of mixing and not input momentum was shown in the fact that varying the velocity ratio had a much greater effect than varying the density ratio. Greater mixing levels exist in the enclosed jet as compared to the free jet, a fact further borne out by the similarity of the potential core velocity ratio relation ship to that found in jets in cross streams where increased mixing is also experienced, although possibly not for the same reasons. An expression has been derived which can be used to predict, with some caution, the path of a jet issuing horizontally into an enclosed space with an initial density difference, up to the point where buoyancy control ceases, and the jet is no longer deflected. This point was found by experiment to be at s = 2.3/k. where k is an empirical constant from the expression for the axial velocity ratio. An attempt was made to model a flame envelope near the mixing tube wall and using the assumption that the envelope was enclosed by the half jet angle it was found that for velocity ratios less than approximately 10, this half jet contour would strike the mixing tube wall whilst the jet was still under the influence of the buoyancy forces.

The purpose of this research programme was to investigate the mode of combustion of Low Pressure Air Atomised Burners since published information on this type of burner is almost non existent. For the necessary experimental work a combustion rig capable of burning 100 litres/hr. of oil was constructed. The rig is a small scale version of those which exist at the International Flame Research Foundation IJmuiden, Holland, except that the combustion space is cylindrical and not rectangular. The combustion chamber's dimensions are 0.61 m. in internal diameter and 3.1 m. in length, with 0.155 m. thick refractory walls. The extent of combustion unmixedness and flame length was determined by means of gas analysis probes. The temperature and emissivity of the flame at six points was measured by a twin-beam total radiation pyrometer. The degree of oil atomisation was estimated using a specially developed liquid nitrogen probe. Such fundamental measurements,plus the more conventional operating measurements, on different oil flames enabled the length of any particular flame and the radiation along it to be measured, for any set of fuel/air input conditions. Using a Stordy-Hauck Type 783 LPA burner, five fuels namely, gas oil, kerosine, 950-sec. fuel oil, 3500-sec. fuel oil and CTF-50 were burnt. For the gas oil experiments, five different diameter nozzles were employed. The minimum excess airs which could be achieved were 3% for every fuel except CTF-50, where it was 5%. In every case all the combustion air as well as the fuel were introduced through the same nozzle and therefore no 'secondary air' existed as such. It is worth pointing out, however, that the orifice design was very complex, resulting in part of the air issuing with the fuel from a central core whilst the remaining air issued through a concentric nozzle around this core. Both streams then mix and eject through an orifice, the diameter of which is assumed to be the 'nozzle diameter'. The present analysis consists of two approaches. Firstly, a straightforward empirical regression analysis based on the observation that the flame length varied linearly with jet momentum, excess air nozzle diameter and the carbon hydrogen ratio of the fuel. This results in the general correlation. The second approach to the problem is by using the theoretical analysis of Bragg which assumes that the flame length is governed, purely, by the reaction rate of the fuel and air. This results in the correlation. [mathematical equations].

Biomass utilisation for synthesis of renewable surfactants has many advantages. The development of alternatives to petrochemically derived products is key, as well as reduction in waste sent to landfill. This thesis focused on two surfactant types and took two approaches towards improving their green credentials. The first investigation aimed at reducing the environmental impact of the synthesis of existing surfactants, alkyl polyglucosides. Zeolites were used as green catalysts to improve product separation and enable catalyst reuse. The key properties of the zeolites were identified as pore size and Lewis acid site strength and density enabling further optimisation to be carried out. Levoglucosan, a glucose-based anhydrosugar, was used as an alternative starting material; the acetal ring improved reaction rate and stereoselectivity compared to the current synthesis from glucose. The second investigation created a range of novel surfactants with potential as drop-in replacements for current surfactants. A bio-derived platform molecule, was used in an environmentally friendly synthesis of surfactants; they were tested for surface activity and critical micelle concentration against the market standards. These compounds were shown to have higher surface activities than the equivalents, indicating they would make more efficient surfactants. In addition, they exhibited lower critical micelle concentration values meaning the replacements could be employed in smaller amounts in formulations, reducing economic along with environmental impact. The use of waste biomass, specifically waste paper, was also investigated to source levoglucosan, for alkyl polyglucoside synthesis. Microwave pyrolysis was tested on waste paper and shown to successfully produce levoglucosan in short reaction times; chemical production from this waste stream is a higher value alternative to recycling. The work detailed within highlighted how a whole process approach is key for future development and that petrochemical depletion does not have to be detrimental to the chemical industry.

A series of biomass wastes from Malaysia known as Malaysian wood pellets, and rubberwood were employed in the present work. Using these materials as the feedstock, two different heating techniques; external heating by means of conventional slow pyrolysis (SP) and volumetric heating by means of microwave pyrolysis (MP) were carried out. Two distinct temperatures; 500°C and 800°C were used. The main objective was to characterise both the microwave-pyrolysed products and slow pyrolysed products including the influence of temperature so as to compare and contrast in terms of yield, and composition of the char, oil and high-value fuel gas (H2) or syngas (H2+CO). Whilst there is an increasing interest in comparing microwave pyrolysis with conventional pyrolysis, much of the research work done in the past focussed on using domestic microwave ovens with power control features where indirect temperature measurements were carried out at different power and time settings. In the present research, the control feature for both heating techniques is similar, where the user can conveniently set the desired pyrolysis temperature and therefore, this would allow for a more direct and reliable comparison of products obtained from conventional pyrolysis and microwave pyrolysis. The research found that the use of the microwave oven system to conduct pyrolysis boosted the production of oil but reduced the total gas yield. The char proportion also reduced when microwave heating method was applied. This research also revealed that the configuration of the microwave oven with mode stirrer and bottom-fed waveguide that produces a cyclic controlled output power of 1000 W at any set temperature has yielded different results when compared to previous studies and so provides a new understanding for the microwave pyrolysis community. The results demonstrated that the microwave-pyrolysed chars were slightly more porous than slow-pyrolysed chars at 500°C. However, at a higher temperature of 800°C, lower surface area was obtained from microwave pyrolysis which can be attributed to significant damage to the char structure as the consequence of high power supplied into the cavity and high temperature used. SEM microphotographs revealed that microwave pyrolysis at 500°C led to the formation of char with clearly defined pore structure. In the case of gaseous product, both heating approaches were found to produce a comparable level of H2+CO content except those produced by MP at higher temperature (800°C). Regarding bio-oil quality, the microwave-pyrolysed oil was found to present compounds with higher aliphatic content and contain less polycyclic aromatic hydrocarbon (PAH) content, which is an added quality value as PAH is toxic to the environment. As demonstrated in the present work, employing a microwave oven to conduct pyrolysis process leads to a great time saving where the woody samples required only 8-10 minutes and 15-16 minutes to reach 500 and 800ºC respectively. On the other hand, the electric furnace used to conduct conventional pyrolysis process demonstrated a slower performance where the time required to reach 500 and 800ºC were about 49 and 72 minutes respectively. This again emphasizes that microwave oven is powerful to speed up the pyrolysis process due to the nature of rapid heating within the internal body of the sample. Additionally, from the viewpoint of energy consumption, microwave oven used approximately 62% less energy than the electric furnace to conduct pyrolysis process and therefore leads to greater energy saving. In the present work, COMSOL Multiphysics software has successfully demonstrated solutions of the numerical coupled electromagnetic and heat transfer equations. The results extracted from the simulation using specified cavity geometry, dielectric properties and thermal properties were seen to agree reasonably well with the experimental data in terms of the temperature profile and heating behaviour of the biomass. The location of hot spots and cold spots from the simulation also agreed with that observed from the experiment. The simulation work has proved that the inhomogeneity of temperature of the biomass is reflected by the local occurrence of hot spots and cold spots. These are influenced by the standing waves of different electric field concentration formed at different areas inside the cavity, and this phenomenon is very common for biomass treatment in a microwave environment. The effect of different positions of the waveguide is remarkable where the bottom-fed microwave energy oven was shown to have a poor electric field distribution. However, when simulation was done on combining the effect of having the microwave energy fed from the bottom and the presence of the mode stirrer, the electric field was greatly improved with the heating distribution of the biomass resembling that obtained from the side-fed microwaves energy oven (usually refers to a common home microwave oven). The effect of having a mode stirrer rotating inside the microwave oven is also pronounced where the mode stirrer acts to stir the electric field strength within the cavity so that a more uniform heating within the biomass can be achieved. The simulation work also demonstrated that the amount of microwave power absorbed in the biomass materials varies according to the changes in loading height of the biomass, and sample positioning inside a microwave oven also contributes to the electric field distortion and heating behaviour of the biomass. Interestingly from the simulation, for a specified microwave cavity, an optimum bed size of biomass was found at 50mm height where maximum microwaves energy absorption takes place. In this sense, more microwaves energy can be converted into heat thereby ultimately helping the biomass to reach the desired pyrolysis temperature in shorter time. The COMSOL modelling on microwave heating therefore has shown to be simple and practical for use as a framework in predicting temperature profile of the biomass and intensity of the electric field.

The scaling up and downstream processing costs of biodiesel from microalgae are major concerns. This study focuses on developing a new method by integrating ozone-rich microbubbles in both the production of microalgae and in downstream processes such as biomass harvesting and lipid extraction. A bacterial contaminant of a green algal (Dunaliella salina) culture was successfully screened, isolated and identified using 16S rRNA gene sequencing as a member of the Halomonas genus (gram-negative). Ozonation of mixed cultures of D. salina and Halomonas for 10 minutes at 8 mg/L reduced the bacterial contaminant without harming the microalgal cells. The sterilisation efficiency reached 66% after 5 minutes and increased to 93% after 10 minutes of ozonation. The algal cell growth performance (biomass concentration) was decreased by over 50% at 10% (v/v) contaminant concentration. Ozonation for 10 minutes at the beginning of the experiment resulted in a biomass reduction of 28.6%, which suggests that ozonation at the beginning of experiment can control the contamination. The optimum values for three parameters (culture media volume, ozone concentration and ozonation time) suggested by the statistical software were 30.63 mL, 8.20 mg/L and 37.7 min, respectively. Harvesting of D. salina cells through microflotation resulted in a 93.4% recovery efficiency. Ozonation of the harvested microalgae for 40 minutes produced three main saturated compounds [2-pentadecanone 6, 10, 14-trimethyl; n-hexadecanoic acid (palmitic acid); and octadecanoic acid (stearic acid)] that consist of 16 to 18 carbons. The main products increased significantly around 156%, 88.9% and 150% for 2-pentadecanone, 6, 10, 14-trimethyl; palmitic acid and stearic acid, respectively when the temperature was increased (60 ˚C), and smaller bubbles (generated by a fluidic oscillator) were introduced during the extraction process. By integrating microbubbles and ozonation into an airlift-loop bioreactor-processing system, this thesis describes a microbubble photobioreactor that delivers in-situ disinfection with microflotation harvesting and lipid extraction in an easily scalable and energy-efficient process.

Increasing concern over climate change and the impact of greenhouse gas emissions as well as diminishing global oil reserves has pushed research into alternative energy. Reducing the cost of microalgae, a promising source for alternative energy, is a key step in commercialising biodiesel production. Currently avenues such as the use of waste stream cost effective cultivation system and efficient harvesting options are being explored for the common goal of establishing commercially viable microalgae production and utilisation schemes. From reviewing the current progress presented in literature this research has identified several aspects of importance to commercialising biofuel production. After identifying several gaps in the literature covering direct comparison of microalgal biomass production between temperate and hot region, a novel investigation utilising a refined computer model was undertaken to compare upstream cultivation of open systems in both temperate and hot climates. The outcome of which suggested the relative importance of light over temperature for the cultivation of microalgae in an open pond system. This was then explored further experimentally by setting the temperate light intensity, photoperiod and temperature conditions for three months representing summer and winter seasons. The results of this novel adaptation of seasonal highs and lows data of a temperate climate (UK) indicated that a more effective direction of intervention is the investment in additional light-supply in place of a heating-system, which is more than likely to yield higher algal biomass for biofuel production. Finally, an approach was made towards engaging more economical aspects of the process from upstream cultivation of waste stream based nutrients (leachate) with a native microalgae strain for the first time, to downstream dewatering of algal biomass with innovative improvements to energy efficient forward osmosis technology by uniquely assessing microalgae nutrient-based draw solution. The results both indicated the real potential of utilising these cost efficient methods at a lab scale. The ultimate goal of the project was to combine the research efforts for both cultivation (upstream) and harvesting (downstream) to assist in the understanding of the commercial viability of biofuel production from microalgae.

Hydrothermal processing has received increased interest mostly in the area of waste conversion to higher density fuels. However in addition to energy generation from these materials, it has become a promising route for nutrient extraction and recovery from either the solid or aqueous products depending on the processing temperature. This research was carried out in phases with the aim to improve extraction of nitrogen and phosphorus from various nutrient-rich wet wastes and the potential to recover these nutrients by biological means or by adsorption unto biochar. The initial study was on various hydrothermal processing routes – thermal hydrolysis (TH), hydrothermal carbonisation (HTC), hydrothermal liquefaction (HTL) and supercritical water gasification (SCWG) at 170°C, 250°C, 350°C and 500°C respectively using high moisture and high nutrient feedstocks namely microalgae, digestate, swine manure and chicken manure. Experiments were conducted with 10:1 water: solid ratio and 1 hour residence time except for SCWG which was 30 minutes with 15:1 water: solid ratio. The fate of N, P and other inorganics from each feedstock during these processes were investigated as well as the product yields, composition of the aqueous products and solid products. The results indicate that feedstocks behave differently during hydrothermal processing with the composition and yields of by products depending largely on feedstock composition and processing temperature. Highest solid yields were obtained at lowest temperatures while highest gas yields were obtained at the highest temperature. HTL favour formation of highest biocrude. Aqueous products from lower temperatures contain higher P levels (mainly organic-P and less phosphate) and lower N levels (mainly organic-N and less NH3-N). At higher temperature it is vice versa. Extracted P depends on Ca, Mg and Fe in unprocessed feedstock. P is immobilised in solid product at higher temperatures. TOC in aqueous product decrease with increasing processing temperature. The effect of additives on nutrient extraction during low temperature processing –Thermal hydrolysis at 120°C and 170°C as well as HTC at 200°C and 250°C using different reagents - alkali (0.1M NaOH), mineral acid (0.1M H2SO4) and organic acids, (0.1M CH3COOH and 0.1M HCOOH) was investigated. All experiments were performed with 10:1 water: solid ratio in high pressure 600 mL Parr batch reactor for 1 hour. The nutrient mass flow balance during these processes, the composition of the aqueous product and solid products were investigated. The results indicate that TN is significantly affected by temperature rather than pH. NH3-N in aqueous product increases with increasing temperature while organic- N reduces. Phosphorus extraction is pH and temperature dependent and further enhanced with additives. Acidic conditions favour phosphorus extraction especially with H2SO4 at all temperatures; highest (94%) extracted using H2SO4 at 170°C and presents opportunity for nutrient recovery. Neutral or basic conditions immobilise P in hydrochar and offers potential route for manure management as P-loss is reduced in the environment. Mg, Na and K are mostly extracted into aqueous product, while Ca and P concentrate in solid product as temperature increases. Acidic conditions extracted higher levels of micronutrient compared to water or NaOH. Generally micronutrients were more in the solid for most additives except H2SO4 while Ni and Al were mostly in the solid products. Microwave pre-treatment of various feedstocks such as sewage sludge, microalgae, digestate and manures was performed with 15:1 water: solid ratio at 120°C for 15 minutes. Also the influence of additives on nutrient extraction from swine manure was also investigated. Results show that aqueous products contain significant levels of N and P; nitrogen mainly as organic-N rather than NH3-N for all feedstock while it was mainly as organic-P for sewage sludge and digestate and more as phosphate with microalgae and manures. High TP was extracted with acidic reagents rather than with water or NaOH. With most additives, N in aqueous product was mainly as organic-N than NH3-N while P in the aqueous product was mainly as phosphate rather than organic-P. Aqueous products contain most K and Na while the residues contain most Ca, Mg, P and micronutrients for most feedstocks. Acidic conditions most especially with H2SO4 extracted more Ca, Mg, P, Co, Mn, and Zn unlike neutral or alkaline conditions. In comparison with conventional heating, microwave heating generally extracted more nitrogen and phosphorus into the aqueous products. Biological recovery of nutrients using various SCWG aqueous waste streams showed significant autotrophic growth of Chlorella in the diluted aqueous products except for the aqueous product from SCWG of Chlorella diluted at 1:50. Chlorella was able to utilise ammonium as a source of nitrogen. Higher dilutions of 1:400 had insufficient nutrients to promote growth. Biomass obtained from 1:50 dilution of catalysed SCWG of S. latissimi, L.digitata, sewage sludge and 1:200 dilution of SCWG Chlorella were comparable with biomass obtained using the standard Bold’s Basal Media. The recovered biomass could be used as feedstock for biodiesel or lipid extraction. Physical recovery of phosphate from H2SO4 extracted aqueous products by adsorption using Mg modified biochar shows that phosphate adsorption is affected by concentration and pH. Highest adsorption was achieved with 250 mg/L while higher adsorption efficiency was achieved at pH 8 and 9 compared to pH 7, precipitating more calcium phosphate on the biochar. Phosphate adsorption did not occur at lower/acidic pH conditions. There was no likelihood of struvite precipitation as EDX analysis showed no additional nitrogen and Mg in the adsorbed chars.

Biochars and hydrochars generated from organic waste streams such as forestry waste (Oak Wood), treated municipal waste, Digestate, Greenhouse waste (Paprika), Green waste and Pig manure have been characterized. In addition, model compounds; cellulose hemicellulose and lignin were also processed under identical conditions. Under standard conditions, the biochar yields ranged from 26% to 69% for biochar and 20% to 75% for hydrochar. Model compounds (lignin, cellulose and hemicellulose also had similar yields of 21% to 75%. Temperature was observed to have a great impact on biochar and hydrochar yields as they decrease with increasing temperature. Other process conditions such as time, doubling solid and additives such as acetic acid, 1%O2 and plastics also had similar impact on the yields of biochar and hydrochar. It also was observed that the biochemical components of the feedstock had no interaction, with each component decomposing separately. The fate and levels of macro nutrients, micro nutrients and heavy metals were also determined with most metals within the quality standards of the International biochar initiative and the European biochar certificate. Waste biochars were observed to have more nutrients when compared to woody biochars. Both nutrient and metal concentrations in the biochars and hydrochars were affected by the type of feedstock, processing technique and processing temperature with the elements increasing with increase in temperature, while some of the nutrients and metals were partitioned in the aqueous phase using hydrothermal carbonization technique. Acetic and formic acids used as additives extracted more metals into the aqueous phase, but the results are comparable to the metals extracted with water. Adsorbed organic hydrocarbons from the biochars and hydrochars were also determined. The Influence of processing conditions and feedstock composition on the nature and yields of extractable hydrocarbons, water extractable organic carbon (WEOC) and water extractable organic nitrogen is investigated. The nature of the hydrocarbons adsorbed onto the biochar and hydrochar has also been assessed using GC-MS, size exclusion chromatography and 1H NMR following exhaustive solvent extraction. Levels of polycyclic aromatic hydrocarbons (PAH) have been determined using single ion monitoring (SIM) from the extracted tars. Additional insight into the chemical and structural nature of the tars has been investigated using 1H NMR, FTIR and size exclusion chromatography. The levels of PAH adsorbed onto biochar are dependent upon feedstock and processing conditions. The levels of PAH ranged from 1.43 µg/g to 3.37 µg/g for hydrochars at 250°C, 1.63 µg/g to 9.79 µg/g for biochars at 400°C and 2.12 µg/g to 6.50 µg/g for biochars at 600°C respectively and were dependent on biomass, pyrolysis temperature, and time. With increasing pyrolysis time and temperature, PAH concentrations generally increase. Total concentrations were below existing environmental quality standards for PAH in soils. Total PAH concentrations in the hydrochars are comparable to biochars and fall between and fall within the quality standards. The levels of non PAH extractable hydrocarbons are higher at the lower temperature processing and include oxygenated hydrocarbons and nitrogen heterocycles although size exclusion chromatography suggests the majority of these tars have a high molecular weight. Hydrochars contain higher levels of tar compared to biochars. 1H NMR indicates the tars contain higher levels of aliphatic hydrogen in methyl or methylene groups. Thermal desorption GC-MS indicates that lower molecular weight hydrocarbons are also present adsorbed on both pyrolysis and HTC chars. This is not observed following solvent extraction due to loss on evaporation. Toxicity tests of the oak and municipal solid waste chars was observed not to have a toxic effect on a pure culture of Pseudomonas aeruginosa, a common microorganism in the soil.