Abstract Biomass is seen as an alternative material to help reduce the dependency of fossil fuel usage in energy- and product-based application. In this thesis, the conversion of biomass, especially agricultural waste, to value added products through hydrothermal carbonisation (HTC) process were investigated. The aim of this research work is to deliver information on the suitability and practicality of the hydrothermal carbonisation process as an effective biomass conversion technology, in particular for palm oil wastes. The HTC process requires sub-critical water medium during the procedure to produce solid products (biocarbon) as the main products. Agricultural waste is classified as biomass material and normally generated in large quantity. In this work, two types of agricultural waste will be studied, which are palm oil empty fruit bunch (EFB) and wood chips (WC). The effects on the operating temperature, time and amount of water usage on the yield and carbon conversion for both materials were examined. A purpose built pressure vessel was designed, with the capacity to be operated up to 230°C and 30 bars. In addition, a program was constructed by using Lab VIEW software to control and record the operation. The characteristics of the biocarbon from EFB and WC were carried out through elemental, calorific, SEM, FTlR, pyconometer and RGB colour model, to examine the correspondence of the biocarbon characteristics with the operating conditions. The HTC process converts the EFB and WC into higher percentage of carbon content solid products. Based on these analyses, the increment of the operating temperature offer more improvement on the biocarbon quality compared to the residence time. The carbon conversion of EFB's biocarbon (operated at 220°C for 22 hours) increased for 20% compared to the raw EFB (43.8% of carbon). In addition, the calorific value of EFB's Abstract biocarbon increased from 17.7 to 28.2 Ml/kg, which is nearly similar with the value of lignite (26.8 MJlkg). A kinetic calculation of the process was calculated by combining the shrinking core model (SCM) and Arrhenius equation. The rate constant for both EFB and WC varies from 0.044 to 0.1 04s·l. Also, comparison on the economic calculation for direct combustion of EFB materials before and after the conversion process was carried out. Based on this calculation, it can be stated that the combustion process is not profitable for the HTC process' biocarbon because this process require quite a lot of energy. The usage of the biocarbon as plantation area was verified by using these products as soil conditioner in the radish growth starts and substrates in mushroom cultivation process. Finally, it can be conclude that the HTC process is practicable method to convert biomass into value added material. In future, improvement of the methodology such as an addition of catalyst in the process and agitator to the rig can be done to obtain higher yield. Also, depth investigations on the biocarbon behaviour in soil medium and effect on the growth and quality of plant is suggested. 11

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As a result of global climate changes brought about by human activity, more sustainable sources of energy are being sought as alternatives to fossil fuels. Biomass is of particular interest as a sustainable source of energy since it does not contribute to net CO2 emissions. Reforming of methane derived from biomass with CO2 may form the basis of an efficient means to produce synthesis gas which has many applications m the petrochemical and allied industries. The objective of this study was the investigation of CO2 reforming of methane (simulating biogas) over effective supported nickel catalysts capable of long term operation without significant loss of activity and stability.

Environmental preservation concerns, coupled with those of energy supply security, are leading to a push for alternative fuels that are both green and sustainable. Therefore, biomass, which is a renewable low carbon energy source, is being increasingly utilized worldwide. The use of biomass in thermochemical conversion is not without problems, some of which are related to the inherent alkali metal content present in these types of fuels. The work conducted for this thesis mainly deals with topics related to thermal degradation kinetics of biomass and the influence of alkali metals on these kinetics, as well as their effects on the thermal behaviour of the fuel. Torrefaction is also studied with respect to kinetics studies, and the effects of mineral content. Thermal degradation was studied using thermogravimetric analysis (TGA) and kinetic models were evaluated to address two questions; first, what method of data analysis is appropriate for extracting reliable kinetic data from TGA experiments? Second, what kinetics are most suitable for high heating rate situations such as those present in pulverized fuel power stations? It was found that for low heating rate experiments (10 Klmin), the global first-order reaction kinetic models that tend to yield low activation energies (E), such as the reaction rate constant method, work well. High E kinetics can also work well at low heating rate, but only if the reaction is assumed to be due to the sum of a number of individual steps. For example, those derived when assuming the biochemical components degrade independently, or using the functional group approach. For higher heating rates (>103 Kls) high E kinetics predict conversion well, and this can be rationalized since primary cracking reactions will dominate under these conditions. However, at heating rates of 105 Kls and temperatures of 1500 QC (i.e., flame conditions), a compensation on the rates is seen and the choice of rate parameters is less critical. Two sets of kinetic data, E = 178.7 kJ/mol, A = 2.2 x 1013 S-1 and E = 48.7 kJ/mol, A = 6.84 x 103 S-I, both predict conversions in keeping With the available experimental data. The effects of alkali metals (K, Na, Cs) on thermal degradation kinetics of SRC willow in pyrolysis, combustion were studied using TGA, and single particle burning in a methane-air flame. The results revealed that all three metals had a strong and similar catalytic effect on pyrolysis and combustion. Combustion under flame conditions also showed a stark contrast between the strongly catalyzed degradation of samples in the presence of alkali metals, and the uncatalysed degradation of mineral-free samples. As with the low heating rate results, at flame conditions, the metal-impregnated samples behaved similarly to each other, implying that a similar thermal degradation. mechanism is followed when woody biomass contains any of the alkali metals. A mathematical expression directly linking the inherent potassium and sodium content of SRC willow to its thermal degradation kinetics was developed through modifying a Langmuir-Hinshelwood relation and applying it to pyrolysis data. This relation yields a maximum reaction rate and a metal saturation constant that can be used to predict a reaction rate of willow based on the pyrolysis temperature and the concentration of either of the metals in the biomass sample. I.e. the maximum reaction rate constant of 3.26 x 10-3 (S-I) and the potassium saturation constant of 0.56 wt% can be used to derive the pyrolysis reaction rate of any willow sample with a known potassium concentration. Similarly, a maximum reaction rate of 3.27 x 10-3 (S-I) and a sodium saturation constant of 0.36 wt% can be used to derive a reaction rate for any willow sample with a known sodium concentration. Ab initio (Density Functional Theory method) modelling was employed to explore the chemical mechanisms involved. Cellobiose was used as a model for cellulose. The cellobiose structure was first optimized at the HF level, and then at the B3L YP DFT level with a 6-31G(d) basis set and the structure frequency was checked to ensure the system was at ground state. The models showed that that both metal ions form multiple interactions with the hydroxyl and ether bonds in the cellulose structure. Structures with metal chelated at the C6 position in the ring have interactions with four oxygen atoms, while metals at the C2 position have interactions with only two oxygen atoms, although inter-molecular chelation between cellulose chains has not been considered. Structures are more stable when potassium or sodium can coordinate to more oxygen groups. Nevertheless, in all the structures investigated, chelation of potassium or sodium causes a change in the conformation of the rings (twisting) which may activate the structure towards cracking. The final area of investigation in this thesis is in torrefaction, a mild pyrolysis process. Torrefied biomass has many advantages over untreated biomass, but its ashcharacteristics remain similar to the parent biomass. In this thesis, inherent metals were removed prior to torrefaction. Impact on ash behaviour of this resultant fuel and the torrefaction process itself are reported. More specifically, the work examined the effects of altered mineral content (through a chemical fractionation procedure involving successive washings of the fuel in water, ammonium acetate, and hydrochloric acid), on the torrefaction, of four biomass fuels (SRC willow, Miscanthus, eucalyptus, and wheat straw), as well as on the pyrolysis and the ash behaviour of the torrefied material. Washing prior to torrefaction significantly reduced the ash content of the fuels, and ameliorated the ash fusion temperatures. The pyrolysis reaction rates of the HCI treated and torrefied fuels were found to be the highest, presumably due to the changes in the biomass structure caused by the acid. The results suggest that water washing is the most useful pre-treatment for the preparation of torrefied fuels. Washing with ammonium acetate or HCI would not be feasible because of the small advantage gained, the high costs induced, and the environmental implications. The significance of the impact of these changes in composition and reaction rates depends on the end application, power station or domestic heating. In the case of power station applications, washing with water reduces the ash content, and improves the ash melting behaviour of the remaining ash, which may be advantageous particularly in the case of straw; the slight increase in N would not be significant because of the normal NOx reduction methods used in power stations. In domestic applications the reduction of ash is not so important but the increase in N may be a significant disadvantage.

The aim of this project was to extract and fractionate waxes from abundant and low-cost under-utilised renewable resources using a green alternative technology. Through a review of the literature, the waxes covering agricultural by-products such as straw were identified as a potential source of high value chemicals for a wide range of applications. Wheat straw waxes were extracted using organic solvents to demonstrate that straw contained high value wax compounds including free fatty acids, fatty alcohols, alkanes, wax esters, sterols, aldehydes and β-diketones. The solvent properties did not affect the composition of the extracts but changed the relative abundance of the different compounds. Linear solvation energy relationship (LSER) was used to model the extraction selectivity relating to total extraction yield and the various wax compounds. Lipophilic and aqueous fractions were separated and LSER results identified that the solvent properties affect only on the quantity of aqueous fraction recovered indicating the selectivity of the solvent. Extraction of wheat straw wax was carried out using a more environmentally friendly supercritical CO2 extraction. The compositional profiles can be tuned by the manipulation of temperature and pressure and compared with the organic solvent extractions. Optimisation of temperature and pressure was carried out and the total crude yields and wax chemical group yields were modelled using the Chrastil equation to gain a better understanding of conditions required to achieve optimum extraction. The optimisation was used as part of the industrial collaboration scale up with Sundown Products Limited and Evonik Industries where a total of three tonnes of wheat, barley and oat straws were extracted using supercritical CO2 which yielded approximately 60 kg of wax. The three cereal straws were selected based on yield and composition as raw materials for the scale up from the biomass screen of seven different straws using hexane and ethanol extractions. Economical assessment was carried out based on the scale up trial and it was concluded that currently the cereal straw wax would cost £12 per kg which is about 2 – 3 times higher than commercial waxes. The straw waxes were characterised and physical properties such as melting point were determined and found to be similar to commercial waxes such as beeswax. Fractionation by scCO2, GPC and saponification were used to further separate the wax products for formulation trials and product tests with the project sponsor, Croda. The crude wax products were deeply coloured and highly hydrophobic with no emulsification properties therefore applications such as coatings and polishes were suggested.

Biomass is an important new energy source because it is indigenous to every part of the world, inexpensive and renewable. Malaysia's ability to produce and consistently export a large quantity of high quality palm oil has made it one of the major vegetable oil exporters in the world. By-products and waste from the palm oil mills are generated in significant amounts and mainly consist of empty fruit bunches, oil palm stone, oil palm shell, palm kernel cake and palm oil mill effluent. Some of this waste is currently used as fuel for boilers with low energy efficiency, as a soil conditioner, or in furniture making. There is a significant interest in recovering energy from oil palm shells and extensive research has been carried out in this area in other studies. However, research on energy production from oil palm stone (OPS) and palm kernel cake (PKC) is very limited. Waste from the oil palm industry, especially OPS and PKC, is abundant and could help to meet the energy demand if properly managed. The main objective of this PhD study was to investigate the main characteristics of the thermo-chemical conversion of OPS and PKC. A series of combustion and pyrolysis tests were carried out using OPS and PKC as the raw materials in fixed bed and pilot-scale fluidised bed reactors. In addition, the FLIC modelling code was used to predict key parameters including theoretical solid temperature and gas composition, and to validate the experimental results from fixed bed combustion tests. Pelletisation was also carried out on PKC due to the loose nature and small size of the particles. In the series of pyrolysis tests using OPS and PKC carried out in a fixed bed reactor, the effects of heating rate at the temperature of 700°C on the yields and properties of the pyrolysis products were investigated. The calorific values of the chars obtained from the OPS and PKC were approximately 28 MJ/kg. The properties of the chars produced were similar to bituminous coal in terms of their calorific value and carbon content. The pyrolysis liquids obtained from the OPS and PKC had calorific values of 21-38 MJ/kg. The pyrolysis liquids obtained from OPS were in the form of a homogeneous liquid, whilst that derived from PKC contained more than half as an aqueous fraction. The results from the fixed bed combustion tests showed that the burning rates increased with an increase in the air flow rate. In addition, results from the FLIC code used to simulate the fixed bed combustion of the oil palm stone showed good agreement with the experimental data in terms of predicting the dynamic temperature profiles along the bed height and the flue gas composition. The effect of primary air flowrate and initial bed temperature were the main parameters investigated in the pilot-scale fluidised bed combustion tests. Both the internal temperature and the surface temperature were found to decrease as the primary air flowrate increased. In all tests CO emissions were less than 0.2%. The emissions of SO2 and HCl ranged from 0.02 ppm to 0.05 ppm, significantly below the levels set by legislation. Stable combustion was observed at a bed temperature of 950°C. The most abundant elements found in the ash were Al, Ca, Fe, K, Mg, Mn, P, S and Si. The variables explored in the pelletisation of PKC were pressure, temperature, fuel moisture content and the effect of binders, which all had significant effects on density and tensile strength. The most favourable conditions for pellet production were found to be a pressure of 9338 psi/64.38 MPa, a temperature of 80-100°C and a fuel moisture content of 7.9%. These pellets had densities of 1184-1226 kg/m3 and tensile strengths of 930-1007 kPa. Adding small amounts of caustic soda (1.5-2.0wt %) to the PKC under these conditions increased the tensile strength to 3055 kPa, whereas starch additives were not found to be effective binders.

Recent national and international emissions legislation, in particular sulphur-dioxide, and the rapid depletion of fossil fuels are forcing power producing industries to look at various alternatives, such as biomass and co-firing techniques. Biomass may be transported to the burners of a pulverised fuel (PF) boiler either mixed with the primary fuel, in general coal, or used in dedicated pipelines. In both cases, the transportation of biomass is different due to its composition, size and shape to the transportation of coal. This thesis investigates the computational modelling techniques for a biomass and biomass blend particle transportation (arboreal and flour) in a pipeline with a transverse elbow, the three-phase flow of a coal and biomass co-fire blend in the primary air annulus of a swirl burner and the combustion of a coal and pelletised straw mixture in a full scale furnace using dedicated burners for the biomass injection. The comparison of spherical and non-spherical drag models, under gravity, as well as Saffman lift, inter-particle collision and randomised impulsive wall collision models has been investigated. Good agreement was observed between the computational fluid dynamics (CFD) simulations and the experimental data, using a non-spherical drag model. In both cases, due to the dilute volume fraction and secondary air flow, inter-particle collisions and lift were insignificant. In the annulus, lateral regions of high particle concentration were predicted, which are not observed physically. Numerical simulations of a 300MWe tangentially fired furnace, co-firing bituminous coal and pelletised straw, have been performed and compared to experimental data. Bituminous coal was co-fired with pelletised straw. Good agreement was obtained between the CFD predictions and the experimental data so that the trends of furnace temperature, NOx emissions and carbon burnout reduction, as biomass load is increased, were observed. Quantitative prediction of unburnt carbon (UBC) and NOx require a more detailed picture of the processes within the furnace at higher temperatures than that currently provided by experimental data.

Renewable biomass derived fuels are of increasing interest for many applications including industrial and aero gas turbines due to the reduction in fossil fuel CO2 and the improvement in energy supply security. The first part of this work investigated the performance of biodiesel as a fuel in low NOx combustors of the type used in industrial gas turbines. This work included comparison with kerosene and co-firing with natural gas and blends of kerosene/biodiesel. In the second phase of this work an aircraft gas turbine APU with diffusion combustion. This investigated the gaseous and particulate emissions using kerosene as a base fuel for comparison with several second generation biofuels, which covered a range of H/C and showed that emissions were correlated with the H/C. The third phase of the work was concerned with renewable or clean coal derived hydrogen combustion using a low NOx flame stabilizer for industrial power generation applications. For the industrial low NOx combustor work a radial swirler flame stabiliser was used. However, the high boiling point of B100 made operation in a premixed vane passage fuel injection mode impossible as ignition could not be achieved. The pilot fuel injector in the centre was the only fuel injection location that B100 would stabilise a flame, due to the central recirculation of burnt gases. A central 8 hole radially outward fuel injector was used as WME (B100) would not operate with radial vane passage fuel injection that is conventionally used for low NOx radial swirlers with natural gas. In the aero engine phase of the research, nine alternative fuels were tested and compared to conventional JetA1 fuel at idle and full power. The results showed that all fuels produced similar level of NOx compared to JetA1 and a slight reduction in CO. A remarkable reduction in UHC was observed at all conditions for higher H/C fuels. The results also show that there was a good correlation between fuels H/C ratio and particle concentrations, particle size and distributions characteristics. The hot idle produced ~20% less particles compare to the cold idle. The alternative fuel blends produced fewer particles than JetA1 fuel. The alternative source of renewable fuels for industrial power generation gas turbines is that of hydrogen derived from renewable or nuclear electricity or from coal or biomass gasification using the water gas shift reaction and CO2 solvent extraction to leave a pure hydrogen fuel. The key problem are in burning hydrogen in gas turbines is that of the increased NOx formation and the increased risk of flashback into the conventional premixing passages used in natural gas low NOx combustors. This work investigated a novel impinging jet configuration that had previously been used successfully with propane and kerosene fuels. It had no premixing so that there could be no flashback. However, the high reactivity of hydrogen did cause a problem with flame stabilization too close to the jet outlets. This was controlled by reducing the proportion of air added to the initial hydrogen jets. NOx emissions lower than alternative designs were demonstrated at simulated high power conditions. This was a practical combustion technique for high hydrogen content fuels with low NOx emissions and no flashback problems.

The need for sustainability, energy security and reduction of global warming has brought many alternative energy sources into the foreground. Already there are well established technologies that can produce renewable energy but when it comes to the production of renewable liquid fuels and chemicals, biomass is the primary feedstock. Biomass is a renewable source of energy that can provide heat, electricity and transport fuels. However, utilisation of biomass posses some limitations such as land availability and competition of energy crops with food crops. In order to overcome these problems "third generation" biofuels from alternative feedstock such as macro-algae have recently come into the foreground. Oceans and seas cover over 70% of the earth's surface, most of which is under exploited, resulting in additional potential for biomass production. This thesis concentrates on the potential for production of bio-energy and chemicals from macro-algae through thermochemical processes such as pyrolysis, combustion and hydrothermal liquefaction. Utilisation of aquatic biomass for production of bioenergy is a very recent concept and there is a lack of information on their thermochemical behaviour. This investigation contributes to a wider study and forms part of the Supergen II bionergy programme investigating the potential for utilisation of macrolage in the UK. This investigation includes a detailed characterisation of the fuel properties and thermal behaviour of a range of wild seaweeds around the UK provided by the Scottish Association of Marine Sciences. In addition, a range of model biochemical components have been investigated, in particular, the model carbohydrates present in macro-algae. Alginic acid, mannitol, laminarin, fucoidan and cellulose are the main carbohydrates present in brown macro-algae. The rest of the plant material comprises of protein and ash. Freshly harvested macro-algae contain 80-90wt% moisture. Their ash content is high, reflecting their high inorganic content. Potassium is the most abundant metal present in macro-algae although other metals are also present including sodium, calcium, magnesium, Their carbohydrate, protein and ash content undergo a seasonal variation during their growth cycle. This variation was found to affect their properties as fuel. Carbon content reaches its maximum during summer - early autumn. During the same period, the inorganic (and thus ash) content is at its minimum suggesting summer - early autumn as the optimum period for harvesting macro-algae for bioenergy. The high carbon and low inorganic content during this period is reflected in its higher heating value but it is still relatively low (13-14 MJ/kg) when compared with terrestrial biomass. The nature of the inhabitant location was found to significantly influence macro-algae fuel properties with samples grown in the open ocean having better fuel properties (higher HHV and lower inorganic content) than samples growing in canals and estuaries. Investigation of the pyrolysis behaviour was performed using thermal analysis such as TGA and Py-GC/MS. The volatile matter evolved during pyrolysis was higher for samples collected during summer and early spring due to their higher carbon content. The main volatiles evolved during decomposition were found to originate either from their carbohydrates or from their protein content. Specific marker compounds were identified for the carbohydrates such as dianhydromannitol, 1-(2-furanyl)-ethanone, 2-hydroxy-3-methyl-2-cyclopenten-1-one and furfural for manitol, laminarin and alginic acid respectively. Proteins are found to produce a range of indoles and pyrroles. Some of the compounds identified may have industrial applications indicating the possibility of producing chemicals through pyrolysis of macro-algae. The high moisture content of seaweed necessitates that significant amounts of water must be removed before this feedstock can be converted by pyrolysis. The high moisture content is similary an issue for combustion which has been assessed by a combination of TGA and characterisation of the biomass. Macro-algae have a low HHV, high halogen content and high ash content and are predicted to have high slagging and fouling behaviour in conventional combustion chambers. This fouling behaviour is predicted through empirical indexes such as the alkali index and is shown to be higher than terrestrial biomass even during summer - early autumn when their inorganic content is at minimum. Typical ash contents vary from 18 to 45wt% and contain mainly oxides of K20, Na2O, CaO and MgO. Pre-treatment prior to combustion can significantly reduce the ash content leading to improved combustion properties, but this also leads to removal of some biochemical components. Using an acid pre-treatment, some of the seaweed's biopolymers, such as mannitol or fucoidan, can be removed presenting the possibility for acquiring valuable chemicals from seaweed before combustion of the residue. An alternative processing route, capable of processing wet feedstocks called hydrothermal liquefaction (HTL) involves the processing of the macro-algae in subcritical water. HTL converts the starting material into four product streams including a bio-crude, a char, an aqueous stream consisting primarily of process water and a gaseous stream. A parametric study of HTL has been investigated using high pressure batch reactors with or without the presence of catalysts. The bio-crude produced from the liquefaction of macrolgae was found to have a high heating value and resembling chemical composition to crude-oil. It can be used directly as a fuel however it still contains significantly high nitrogen levels and will required suitable upgrading (e. g. denitrogenation). The bio-char was found to also have a high heating value. Both bio-crude and bio-char produced from HTL are virtually free of alkali metals suggesting they are suitable for combustion. Reaction conditions such as temperature and the ratio of biomass to water have the greatest influence on product yields and properties. Typical bio-crude yields were in the range of 10 to 19wt% on a daf basis with their HHVs ranging from 32 to 38 MJ/kg. The yields of bio-chars were in similar range (IOwt% to 19wt% on a db) with HHVs between 10 and 26 MJ/kg. An energy balance was calculated in order to investigate the energy required to heat the mixture of macro-algae and water. The energy recovery in the bio-crude and bio-char was relatively low, between 50 and 65%, indicating that a significant portion of the energy content of macro-algae is passing in to the other product streams. The aqueous phase (process water) was found to be rich in metals, especially alkali metals, and sugars, and its composition suggests it maybe possible to utilize it as a fertilizer. A fraction of the sugars present in macro algae (mannitol and laminarin) pass in to the aqueous stream, suggesting there is also potential for fermentetion to bioethanol. The gaseous stream is composed mainly of CO2, N, CO and lower concentrationso H and CH4. The most suitable thermochemical processing route for macro-algae is proposed to be hydrothermal liquefaction and has potential for utilization of all the product streams producing fuels and chemicals using a bio-refinery concept.