The present study has examined the behaviour of a range of biomass/waste derived fuels under downdraft gasification conditions. The aim has been the identification of operating conditions leading to the complete destruction ofthe tars. A two-stage 'hot-rod' fixed-bed reactor has been developed to simulate the operating conditions in a commercial downdraft gasifier. The upper 'hot-rod' reactor simulates the pyrolysis zone of the commercial gasifier. A 1 g batch of fuel is electrically heated from ambient to 500°C at a rate representative of conditions in the upper zone of the commercial gasifier, i.e. few °C/min. In the commercial device, air is injected through a throat part-way down the shaft permittJllg gasification to take place in the lower regions of the gasifier. In the laboratory experiment, the throat has been simulated by a flange with three built-in nozzles through which helium or helium-diluted air may be admitted. This flange joins the upper pyrolysis 'hot-rod' reactor to the lower, tardestruction reactor. A systematic study has been made of the factors that will destroy tar in the lower reactor; these are temperature, presence of a char bed, type of char bed, char particle size, gas residence time and addition of oxygen (as air) at the throat. In the first part of the experimental programme, the emission of tars from a range of fuels pyrolysed in the upper reactor alone has been measured. The fuels used were plastic waste, eucalyptus wood, paper sludge, pine wood and silver birch wood. These were pyrolysed under similar operating conditions, using helium as sweep gas, at atmospheric pressure.,. The reactor was operated at two different heating rates, representing the likely extremes in a commercial gasifier, i.e. 1 °C/s and 10 °C/s, over the temperature range 200 - 500°C, with holding times of 300 s and 900 s at peak temperature and with a helium gas velocity of 0.1 mfs. The results indicate that the pyrolysis-derived tar, char and gas yields varied between the samples, but the trends were similar with increasing temperature; the tar yield increased with increased temperature. It was observed that silver birch wood gave the highest tar yield (at 47% by weight of the fuel fed) in the hot-rod reactor, whilst paper sludge gave the lowest tar yield (19%). As a result of this first phase of experiments, silver birch wood, pyrolysed to 500°C, has been chosen as the standard for the later tar destruction experiments, in the second stage. In the second phase of experiments, tar-laden gas from the upper stage was fed into the lower stage reactor, over the temperature range 700 - 1000°C. The sweep gas velocity was 2 mfs and initially helium, then a airlhelium mixture was added via three injector nozzles. Initial experiments showed that significant extents of tar destruction occur even in the absence of a packed bed in the heated, second stage reactor. Tar yield reduction from the initial value of47% down to 5% has been observed at 800°C. This figure fell to 0.7%, when the reactor temperature was raised to 1000°C. Addition of a char bed to the second-stage reactor achieved further tar reduction, compared to the empty reactor. The size of char particles in~roduced was observed to

No description available.

No description available.

Increasing energy demands in the transport sector, combined with the scarcity of fossil energy sources and the need for climate protection, illustrate the importance of finding alter-native and CO2-neutral sources of energy. This thesis presents the results of research concerning the behaviour of cracked vegetable oil (CVO) during hydroprocessing. The product “hydrogenated cracked vegetable oil” (HCVO) could be an alternative renewable diesel fuel. The experiments were conducted in a high pressure, high temperature reactor. The parameters of investigation under hydrogen atmosphere were: temperature (150-450 °C), initial hydrogen pressure (50-150 bar), and reaction time (1-20 h). These experiments were either thermal or catalytic, whereas the type (CoMo, NiMo and Pd+Pt on Al2O3, HZSM5, Pd and Pt on carbon) and quantity of the catalyst (0.5-5 wt.-%) were additional parameters. Furthermore the influence of an inert reaction atmosphere was investigated. The optimal reaction temperature regarding deoxygenation without coke formation during hydroprocessing was found to be 380 °C. An increase of reaction time, as well as higher initial hydrogen pressure led to increased energy density in the product – the only exceptions were the Pt catalyst and HZSM5, where the gross calorific value (gcv) remained constant with in-creased initial pressure from 100 to 150 bar. Density, viscosity, acid value, iodine number, energy density, chemical and elemental com-position of the HCVO were analysed and evaluated in relation to CVO and diesel fuel. The highest gcv was 46.1 MJ/kg using the Pt catalyst; CoMo, NiMo and Pd led to 44.8-45.1 MJ/kg. These are comparable to diesel fuel. A kinetic model was developed to estimate the thermal deoxygenation of CVO at different reaction temperatures. Absorption of hydrogen in the liquid phase was investigated in catalytic and non-catalytic processing. In the presence of precious metal catalysts, substantial absorption of hydrogen and therefore extensive deoxygenation and saturation of double bonds in CVO were observed.

Improving the availability of secure energy supplies for the poorest rural communities is central to development efforts. World-wide, climate change concerns have led to growing interest in renewable sources, including modern forms of bioenergy. Drivers behind its adoption are diverse, location and scale dependent, and result in multi-level trade-offs. Although impacts are context-specific, bioenergy production and use have a wider impact on issues including deforestation, biodiversity loss, water shortages and food price increases. At local levels reports of labour exploitation, loss of local land rights, market interference and resource depletion are alarming. However, bioenergy projects continue to be promoted and implemented for potential social, environmental and economic benefits, particularly in rural areas of developing countries. Efforts to ensure sustainable bioenergy at international levels are emerging, with varying success. Existing market and legislative efforts are often insufficient to ensure positive socio-economic and environmentally sound outcomes locally. This thesis therefore aims to provide two approaches to incorporate socio-economic aspects in planning for sustainable bioenergy production in rural areas of developing countries. The research uses India and Uganda as substantive case studies. Based on these experiences, and in order to better understand the social effects of bioenergy feedstock production, a straightforward two step methodology for assessing social effects of bioenergy projects in developing countries is proposed, intended to be embedded within a planning for sustainability framework. One of the main barriers to success has been effective multi-stakeholder consultation (MSC). To address this, a second approach is conceived, for identifying and understanding stakeholders and their dynamics (in terms of roles, requirements and risks). Initially this focuses on liquid biofuel production models in India using five Jatropha curcas L.-based biodiesel production models in Chhattisgarh State, where the significant distinctions between them are: land ownership and value chain; and market end use and route. When analysing social impacts locally the risks and responsibilities of different stakeholder groups must be considered. The approach is then trialled on eight predominately theoretical models of woody biomass for gasification in Uganda, where the main distinctions are land ownership and feedstock type. Key social issues vary by whether models are corporately or farmer/NGO led, and what production arrangements were in place. Scale of plantation and market size were found to be important; small, privately owned models are unlikely to benefit landless poor and could deplete resources without strategic planning, while larger projects employ more, but often have longer term natural resource impacts. Bioenergy initiatives which collaborate with the rural poor and landless are found to be most likely to result in socio-economic rural development, and one of the proposed Ugandan models which potentially offers social benefits is analysed in terms of additional outcomes. The analysis concludes it is: economically viable; will produce significantly less carbon than generators (dependent on plantation productivity); will not impact local water resources significantly (if converting rangeland); and requires capacity building and stakeholder participation from the outset to promote local ownership and troubleshooting ability. The importance of strategic planning and departmental coordination, and the need for a pilot case to allow the technology to be tested, are shown. It is concluded that participation of stakeholders in the sustainability planning process is crucial, and the approaches proposed in this thesis are robust facilitating tools. Context-specific assessments, such as these, are essential in planning for sustainable bioenergy production and would be expected to facilitate successful MSC and ultimately sustainability planning, improving its contribution to policy making.

Biomass has been proven a viable feedstock in several bioindustries and theoretically has potential for new bioproducts. There is plenty of scope in research and development to synthesise feasible integrated processes for a wider range of products. There should be strategies for manipulating characteristics of biomass, which consider economic, social and environmental aspects, along with technological feasibilities. The aim of the study reported in this thesis was to demonstrate the functioning of the suggested evolutionary optimisation method in conceiving heuristics for biorefineries. The method involved carrying out optimisations to the superstructures, which were generated by following the predicted heuristics. The procedure followed the PAR method, which is equivalent to Siirola's general design paradigm (1996a). The base case selected was the corn dry milling ethanol process which produces DDGS asis the by-product. The models developed to evaluate the heuristics emphasised on mass balance and economic analysis. The mass balance was generated by followining a particular matrix operation, which was one of the contributions of this study. Remainder and Generation terms were suggested, for which Key-factor, Remainder and Generation matrices were required. Incorporating new units to the base case model would be easier once these two terms have been identified.

The projected decline in fossil fuel availability, environmental concerns, and security of supply attract increased interest in renewable energy derived from biomass. Fast pyrolysis is a possible thermochemical conversion route for the production of bio-oil, with promising advantages. The purpose of the experiments reported in this thesis was to extend our understanding of the fast pyrolysis process for straw, perennial grasses and hardwoods, and the implications of selective pyrolysis, crop harvest and storage on the thermal decomposition products. To this end, characterisation and laboratory-scale fast pyrolysis were conducted on the available feedstocks, and their products were compared. The variation in light and medium volatile decomposition products was investigated at different pyrolysis temperatures and heating rates, and a comparison of fast and slow pyrolysis products was conducted. Feedstocks from different harvests, storage durations and locations were characterised and compared in terms of their fuel and chemical properties. A range of analytical (e.g. Py-GC-MS and TGA) and processing equipment (0.3 kg/h and 1.0 kg/h fast pyrolysis reactors and 0.15 kg slow pyrolysis reactor) was used. Findings show that the high bio-oil and char heating value, and low water content of willow short rotation coppice (SRC) make this crop attractive for fast pyrolysis processing compared to the other investigated feedstocks in this project. From the analytical sequential investigation of willow SRC, it was found that the volatile product distribution can be tailored to achieve a better final product, by a variation of the heating rate and temperature. Time of harvest was most influential on the fuel properties of miscanthus; overall the late harvest produced the best fuel properties (high HHV, low moisture content, high volatile content, low ash content), and storage of the feedstock reduced the moisture and acid content.

The simultaneous use of willow as a vegetation filter and an energy crop can respond both to the increasing energy demand and to the problem of the soil and water contamination. Its characteristics guarantee that the resources are used economically. As a vegetation filter, willow uptakes organic and inorganic contaminants. As a fast growing energy crop it meets the requirements of rural areas without the exploitation of existing forestry. The aim of the research was to gather knowledge on the thermal behaviour of willow, uptaking contaminants and then used as an energy crop. For this reason pyrolysis experiments were performed in two different scales. In analytical scale metal-contaminated wood was investigated and bench scale pyrolysis experiments were performed with nitrogen-enriched willow, originated from a wastewater treatment plant. Results of the pyrolysis showed that 51-81 % of the wastewater derived nitrogen of willow was captured in the char product. Char had low surface area (1.4 to 5.4 m2/g), low bulk density (0.15–0.18 g/cm3), high pH values (7.8–9.4) and high water-holding capacity (1.8 to 4.3 cm3/g) while the bioavailability of char nutrients was low. Links were also established between the pyrolysis temperature and the product properties for maximising the biochar provided benefits for soil applications. Results also showed that the metal binding capacity of wood varied from one metal ion to another, char yield increased and levoglucosan yield decreased in their presence. While char yield was mainly affected by the concentration of the metal ions, levoglucosan yield was more dependent on the type of the ionic species. Combustion experiments were also carried out with metal-enriched char. The burnout temperatures, estimated ignition indices and the conversion indicate that the metal ions type and not the amount were the determining factors during the combustion. Results presented in the Thesis provide better understanding on the thermal behaviour of nitrogen-enriched and metal contaminated biomass which is crucial to design effective pyrolysis units and combustors. These findings are relevant for pyrolysis experiments, where the goal is to yield char for energetic or soil applications.

The production of agricultural and horticultural products requires the use of nitrogenous fertiliser that can cause pollution of surface and ground water and has a large carbon footprint as it is mainly produced from fossil fuels. The overall objective of this research project was to investigate fast pyrolysis and in-situ nitrogenolysis of biomass and biogenic residues as an alternative route to produce a sustainable solid slow release fertiliser mitigating the above stated problems. A variety of biomasses and biogenic residues were characterized by proximate analysis, ultimate analysis, thermogravimetric analysis (TGA) and Pyrolysis – Gas chromatography – Mass Spectroscopy (Py–GC–MS) for their potential use as feedstocks using beech wood as a reference material. Beech wood was virtually nitrogen free and therefore suitable as a reference material as added nitrogen can be identified as such while Dried Distillers Grains with Solubles (DDGS) and rape meal had a nitrogen content between 5.5wt.% and 6.1wt.% qualifying them as high nitrogen feedstocks. Fast pyrolysis and in-situ nitrogenolysis experiments were carried out in a continuously fed 1kg/h bubbling fluidized bed reactor at around 500°C quenching the pyrolysis vapours with isoparaffin. In-situ nitrogenolysis experiments were performed by adding ammonia gas to the fast pyrolysis reactor at nominal nitrogen addition rates between 5wt.%C and 20wt.%C based on the dry feedstock’s carbon content basis. Mass balances were established for the processing experiments. The fast pyrolysis and in-situ nitrogenolysis products were characterized by proximate analysis, ultimate analysis and GC– MS. High liquid yields and good mass balance closures of over 92% were obtained. The most suitable nitrogen addition rate for the in-situ nitrogenolysis experiments was determined to be 12wt.%C on dry feedstock carbon content basis. However, only a few nitrogen compounds that were formed during in-situ nitrogenolysis could be identified by GC–MS. A batch reactor process was developed to thermally solidify the fast pyrolysis and in-situ nitrogenolysis liquids of beech wood and Barley DDGS producing a brittle solid product. This was obtained at 150°C with an addition of 2.5wt% char (as catalyst) after a processing time of 1h. The batch reactor was also used for modifying and solidifying fast pyrolysis liquids derived from beech wood by adding urea or ammonium phosphate as post processing nitrogenolysis. The results showed that this type of combined approach was not suitable to produce a slow release fertiliser, because the solid product contained up to 65wt.% of highly water soluble nitrogen compounds that would be released instantly by rain. To complement the processing experiments a comparative study via Py–GC–MS with inert and reactive gas was performed with cellulose, hemicellulose, lignin and beech wood. This revealed that the presence of ammonia gas during analytical pyrolysis did not appear to have any direct impact on the decomposition products of the tested materials. The chromatograms obtained showed almost no differences between inert and ammonia gas experiments indicating that the reaction between ammonia and pyrolysis vapours does not occur instantly. A comparative study via Fourier Transformed Infrared Spectroscopy of solidified fast pyrolysis and in-situ nitrogenolysis products showed that there were some alterations in the spectra obtained. A shift in frequencies indicating C=O stretches typically related to the presence of carboxylic acids to C=O stretches related to amides was observed and no double or triple bonded nitrogen was detected. This indicates that organic acids reacted with ammonia and that no potentially harmful or non-biodegradable triple bonded nitrogen compounds were formed. The impact of solid slow release fertiliser (SRF) derived from pyrolysis and in-situ nitrogenolysis products from beech wood and Barley DDGS on microbial life in soils and plant growth was tested in cooperation with Rothamsted Research. The microbial incubation tests indicated that microbes can thrive on the SRFs produced, although some microbial species seem to have a reduced activity at very high concentrations of beech wood and Barley DDGS derived SRF. The plant tests (pot trials) showed that the application of SRF derived from beech wood and barley DDGS had no negative impact on germination or plant growth of rye grass. The fertilizing effect was proven by the dry matter yields in three harvests after 47 days, 89 days and 131 days. The findings of this research indicate that in general a slow release fertiliser can be produced from biomass and biogenic residues by in-situ nitrogenolysis. Nevertheless the findings also show that additional research is necessary to identify which compounds are formed during this process.

Fossil fuels such as coal, oil and natural gas are, by the nature of their formation. a finite resource. Fossil fuel resources will eventually deplete or become uneconomical to use. If mankind is to maintain or improve its current quality of life over future generations, alternative means of producing usable energy and materials must be found. One feasible approach is bio-refining, which uses biomass to produce usable energy and materials from renewable sources. It has been stated that the main factor against the viability of a bio-refinery is the lack of available technology. The work described within this thesis aimed to enhance the technology in two areas within a potential bio-refinery; the depolymerisation of lignin to produce platform chemicals and the polymerisation of rac-lactide to produce bio-plastics. Chapter 2 contains the synthesis of a range of novel zinc(II) and aluminium(II1) heterogeneous silica tethered initiators for the ROP of rac-lactide were synthesised as well as their homogeneous silsesquioxane analogues. The heterogeneous complexes produced polylactide of reasonable molecular weight in a well controlled fashion. with Si-(L-HO)Al showing a degree of stereocontrol (Pr=0.32). ICP-AES analysis showed a reduction in the metal content of the polymer produced by heterogeneous initiators. A polymer synthesised by the heterogeneous Si-(LtBUO)AI complex contained 431 ppm Al compared to 2500 ppm Al when its homogeneous analogue, Al(tbuO)Me2, was used. A novel tetrametallic zinc(II) complex, Zn4(L HO)4(OMe)2Me2, was synthesised, demonstrating serendipitous oxygen insertion into the Zn-Me bond. Chapter 3 involved the synthesis and characterisation of a range of novel zinc(U) complexes based on a β-ketoiminate ligand system with varying steric properties. These were also active for the synthesis of polylactide from rac-lactide but exhibited no stereocontrol. The complexes were active in the industrial preferred melt conditions. Chapter 4 details analytical processes to assess the depolymerisation of lignin under oxidative conditions and a range of model lignin compounds were synthesised. Various approaches were utilised, based on heterogeneous and homogeneous•catalysts. The catalytical coupling of two -OH groups to form an ether moiety was observed in the presence of a Re(VII) complex and H20 2• A range of cobalt and vanadium complexes were synthesised and two solid state structures, CoSaLtBuOO and V(LTBUOO)O, were determined, these were screened for the depolymerisation of lignin and model compounds.