Gasification is a promising technique for transforming solid biomass into a gas that can be used to produce renewable heat, power, fuels or chemicals. Biomass materials, such as forestry residues, can be high moisture, heterogeneous mixtures with low bulk density - properties that make them difficult to handle and convert. Consequently, this means that feedstock pre-treatment is usually necessary in order to facilitate its conversion by gasification. Pre-treatments methods, which include comminution, drying, pelletization, torrefaction, or carbonization will affect the properties of the biomass which will affect their gasification in a fluidized bed. The objective of this thesis was to determine how biomass pre-treatment can influence gasification in a fluidized bed. A single forestry residue was processed using five pre-treatment process levels: sieving (as a surrogate for comminution), drying (moisture content), pelletization, torrefaction, and carbonization. The fractions derived from these processes were gasified in a small pilot-scale air blown bubbling fluidized bed gasifier (feed rate 8 – 25 kg/h). The particle size and form had an impact on the gas composition, tar content, and cold gas efficiency of the gasification. Over the conditions tested, the finest fraction produced a gas with a H2/CO ratio of 0.36 – 0.47 containing 7 – 59 g/m3 tar (gravimetric) at a cold gas efficiency of 30 - 41%. The pellets on the other hand yielded a gas with a H2/CO ratio of 0.89 - 1.14, containing 3 – 37 g/m3 tar (gravimetric) at a cold gas efficiency of 41 – 60%. Drying, torrefaction and carbonization also had an impact on the gasification performance. Carbonization was able to reduce the yield of tar (as measured by gas chromatography) by more than 95% relative to the parent material. Finally, four different forestry residues were gasified in a large pilot-scale bubbling fluidized bed with air and steam-oxygen mixtures (feed rate 200 – 245 kg/h) in order to assess whether the comminution effect could be observed at the large scale. One feedstock with a significant portion of small particles showed the expected effects compared to the feed materials with large feed particles: lower H2/CO ratio, greater tar yield, lower cold gas efficiency while the other feed material containing a substantial amount of small particles did not show these effects.

Made available in DSpace on 2016-06-02T19:19:56Z (GMT). No. of bitstreams: 1 OLIVEIRA_Ricardo_2013.pdf: 1869572 bytes, checksum: 20bae9244cac34b6d1cf25549b89cb99 (MD5) Previous issue date: 2013-02-07 / Universidade Federal de Sao Carlos / The aim of this study was to evaluate the properties of briquettes made from charcoal fines bonded with paraffin. To prepare them were used three fractions of fine coal (20, 35 and 60 mesh) and a binder, the paraffin. Initially, the coal was fragmented into small pieces, milled and sieved and the fines thus produced were mixed and homogenized to the binder in a proportion of 15, 25 and 35%. The mixtures were taken to the oven, so the paraffin is melted and then taken to a laboratory hydraulic pressure where was applied a compression force of 1250 Kgf.cm-2 for 30 seconds. According to the results, the briquettes produced had an increase in heating power in accordance with increase in the content of binder reaching 8588 kcal.Kg-1 in briquettes bound with 35% of paraffin. The ash content was not affected by the binder since the paraffin produces no ash in the process of combustion. It was also accomplished the combustion index test using a combustion device, where temperature vs. time graphs and mass vs. time graphs were generated in order to learn more of its properties in the combustion process. The mechanical strength was indeed an important feature provided by the binder paraffin to the briquettes reaching a diametrical compression strength of 0.785 MPa, significant value compared to the lack of resistance in the briquettes without the binder, and generating fine in percentage of 5.38%, showing high mechanical strength, essential property in the process of transportation and storage. The assay distribution in paraffin briquette showed that the binder migrated to the edges, characterizing it as a binder type film. The higher the content of paraffin binder, the lower the moisture content of the briquettes. The moisture absorption was minimal with average values of 5%, presenting the moisture protection provided by the binder / O objetivo deste trabalho foi avaliar as propriedades dos briquetes produzidos com finos de carvão vegetal aglutinados com parafina. Para confeccioná-los foram utilizadas três frações de fino de carvão (20,35 e 60 mesh) e um aglutinante, a parafina. Inicialmente, o carvão foi fragmentado em pequenos pedaços, moído e peneirado e os finos foram assim produzidos, misturado e homogeneizado ao aglutinante em proporção de 15, 25 e 35%. As misturas realizadas foram levadas à estufa, para que a parafina se fundisse, e posteriormente levadas para a moldagem em prensa hidráulica de laboratório, onde foi aplicada uma pressão de 1250 Kgf.cm-2 durante 30 segundos. De acordo com os resultados, os briquetes produzidos tiveram aumento no poder calorífico de acordo com o aumento no teor de aglutinante chegando a 8588 Kcal.kg-1 nos briquetes aglutinados com 35% de parafina. O teor de cinzas, não foi afetado pelo aglutinante uma vez que a parafina não produziu cinzas em seu processo de combustão, resultado analisado através do ensaio por termogravimetria. Foi realizado também o teste de índice de combustão utilizando um dispositivo-teste, onde gráficos de temperatura vs. tempo e massa vs. tempo foram gerados a fim de se conhecer mais sobre propriedades dos briquetes no processo de combustão. A resistência mecânica foi de fato uma característica importante proporcionada aos briquetes pelo aglutinante parafina chegando a uma resistência a compressão diametral de 0,785 MPa, valor expressivo tendo em vista a ausência de resistência nos briquetes sem o aglutinante; e gerando finos, no ensaio de tamboramento, em porcentagem de 5,38%, evidenciando alta resistência mecânica, propriedade essencial no processo de transporte e armazenamento. O ensaio de distribuição da parafina no briquete mostrou que o aglutinante migrou para as extremidades, caracterizando-o como aglutinante tipo filme. Quanto maior o teor de aglutinante parafina, menor foi o teor de umidade dos briquetes. A absorção de umidade foi mínima com valores médios de 5%, isso evidencia a proteção à umidade proporcionada pelo aglutinante.

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The main purpose of this project was an attempt to modulate and simulate two existing biogas plant, situated in Lidköping and Katrineholm, Sweden and evaluate how the process reacts to certain conditions regarding feeding, layout and substrate mixture. The main goal was to optimize the existing processes to better performance. Both the modeling and simulation were executed in SIMBA#Biogas with accordance to the real conditions at the plant in question. The simulation of each model was validated against data containing measurements of, CH4 yield, CH4 production, TS, VS, NH4-N concentration and N-total concentration. The data was obtained from each plant in accordance with scheduled follow ups. Both models were statistically validated for several predictions. Predictions of N-total and NH4-N concentration failed for some cases. Both plants were tested with new process lay outs, where promising results were obtained. The Lidköping model was provided with a post-hygienization step to handle ABPs. The Katrineholm model was provided with a dewatering unit, where 35% of the centrate was recirculated back to the system. Both setups was configured to yield the highest CH4 production. This study suggests that SIMBA#Biogas can be a tool for predictions and optimizations of the biogas process.

Gasification is a promising technique for transforming solid biomass into a gas that can be used to produce renewable heat, power, fuels or chemicals. Biomass materials, such as forestry residues, can be high moisture, heterogeneous mixtures with low bulk density - properties that make them difficult to handle and convert. Consequently, this means that feedstock pre-treatment is usually necessary in order to facilitate its conversion by gasification. Pre-treatments methods, which include comminution, drying, pelletization, torrefaction, or carbonization will affect the properties of the biomass which will affect their gasification in a fluidized bed. The objective of this thesis was to determine how biomass pre-treatment can influence gasification in a fluidized bed. A single forestry residue was processed using five pre-treatment process levels: sieving (as a surrogate for comminution), drying (moisture content), pelletization, torrefaction, and carbonization. The fractions derived from these processes were gasified in a small pilot-scale air blown bubbling fluidized bed gasifier (feed rate 8 – 25 kg/h). The particle size and form had an impact on the gas composition, tar content, and cold gas efficiency of the gasification. Over the conditions tested, the finest fraction produced a gas with a H2/CO ratio of 0.36 – 0.47 containing 7 – 59 g/m3 tar (gravimetric) at a cold gas efficiency of 30 - 41%. The pellets on the other hand yielded a gas with a H2/CO ratio of 0.89 - 1.14, containing 3 – 37 g/m3 tar (gravimetric) at a cold gas efficiency of 41 – 60%. Drying, torrefaction and carbonization also had an impact on the gasification performance. Carbonization was able to reduce the yield of tar (as measured by gas chromatography) by more than 95% relative to the parent material. Finally, four different forestry residues were gasified in a large pilot-scale bubbling fluidized bed with air and steam-oxygen mixtures (feed rate 200 – 245 kg/h) in order to assess whether the comminution effect could be observed at the large scale. One feedstock with a significant portion of small particles showed the expected effects compared to the feed materials with large feed particles: lower H2/CO ratio, greater tar yield, lower cold gas efficiency while the other feed material containing a substantial amount of small particles did not show these effects.

En France, la consommation d'énergie finale de bioénergies a crû de 35 % lors de la dernière décennie pour atteindre une part de 8,1 % de la demande finale en 2012. Leur développement a été incité car elles sont une source d'énergie renouvelable, elles permettent de réduire la dépendance aux importations d'énergies fossiles et de diminuer les émissions de gaz à effet de serre (GES). Elles sont aussi un moyen de dynamiser les secteurs agricoles et sylvicoles et de maintenir et de créer des emplois non délocalisables.Mais ce développement est soumis à des incertitudes : compétitivité économique vis-à-vis des ressources fossiles et d'autres alternatives renouvelables, disponibilité de la biomasse, choix technologiques, et mécanismes incitatifs. De plus, il est confronté à des controverses. L'accroissement de la demande en ressources biomasse a créé de la tension sur leurs prix et menacé les usages existants, comme le secteur des panneaux bois pour la construction au niveau français et le secteur de l'alimentation à l'échelle mondiale. Leur bénéfice environnemental a aussi été remis en cause, en termes d'émissions de particules fines pour la valorisation chaleur et électricité et en termes d'émissions de GES pour les biocarburants. De nouveaux procédés de valorisation, ne suscitant pas ces controverses, pourraient être privilégiés par le législateur au détriment des procédés actuels.Le but de cette thèse est de baliser un certain nombre de ces incertitudes afin de proposer des stratégies technologique et réglementaire pour les filières bioénergies françaises. Pour cela, nous avons développé un modèle de prospective qui décrit de façon détaillée le secteur des bioénergies et ses technologies de conversion actuelles et futures. Il est basé sur un paradigme d'optimisation qui permet de calculer les trajectoires technologiques de moindre coût, de 2010 à 2050, selon un grand nombre de contraintes qui représentent les spécificités du secteur : disponibilité et coût des ressources, paramètres techniques, économiques et environnementaux des procédés de conversion, etc.Dans une première partie, la démarche prospective est décrite. Elle consiste à analyser dans le détail les filières bioénergies : leur structure actuelle, les points de controverse et les systèmes techniques prometteurs, puis à développer un modèle de réflexion prospective basé sur ces données.Quatre questions d'intérêt stratégique pour la filière sont discutées dans la suite du document. Premièrement, la question du niveau de la demande à laquelle pourrait répondre le secteur selon deux scénarios contrastés de disponibilité de ressources métropolitaines est envisagée. Les trajectoires technologiques sont aussi analysées. Deuxièmement, l'impact d'une évolution du contexte réglementaire ainsi que les bénéfices environnementaux des biocarburants sont appréhendés. La troisième question est celle de l'impact de l'essor de la chimie du végétal sur les bioénergies. Enfin, les stratégies technologiques des biocarburants sont étudiées à l'aide d'une méthode Monte Carlo afin de comprendre les conditions du déploiement des diverses technologies disponibles. / French bioenergy consumption increased by 35 % over the last decade. It reached an 8.1% share in final energy demand by 2012. Bioenergy has been fostered for its many benefits as it is a renewable energy source that increases energy supply independence and that reduces greenhouse gases (GHG) emissions. This sector also maintains and provides job at local level and promotes agricultural and forestry economic development.But the sustainability of this development is now subject to uncertainties: economic performance in comparison to fossil fuels, biomass availability, technological choices, and level of incentives. In addition, it faces several controversial points. Firstly, rise in global biomass demand has implied a rise in prices and it has threatened existing uses, such as wood panel manufacturing in the French building sector and food supply at a world scale. Secondly, environmental performance has been criticized: biomass combustion could emit fine particulate matter and GHG emissions of current biofuel processes may be higher than initially assessed. Consequently, new bioenergy pathways, avoiding these controversies, could be promoted by the policy maker.This PhD thesis aims at assessing these uncertainties to elaborate technological and regulatory strategies for French bioenergy sector. So, we created a prospective model which precisely describes this sector and its current and future conversion pathways. It relies on linear programming optimization paradigm that calculates least cost technological trajectories, from 2010 to 2050. Bioenergy sector is modelled by a large number of constraints: availability and cost of biomass, technical, economic and environmental parameters of transformation processes, etc.In the first part, we describe the prospective approach. It consists in analysing precisely bioenergy pathways: the current structure, the controversial points and the promising processes. Then, we explicit the conception of the prospective model: its data and its assumptions.In the second part, four main strategic points of bioenergy sector are discussed. Firstly, we assess the level of demand that could be fulfilled according to two contrasting scenarios of French biomass availability. Technological mix is then analysed. Secondly, we investigate the consequences of a change in biofuel regulatory context and a reconsideration of their environmental benefits. Thirdly, bio-based chemistry development impact on bioenergy production is evaluated. Finally, biofuel technological strategies are studied with a Monte Carlo approach to enhance the comprehension of the economic and environmental conditions of technology deployment.

Agricultural bioenergy crops (“bioenergy”) are a promising renewable fuel source if carbon (C) emitted during the production and combustion of bioenergy is less than emissions associated with fossil fuel analogs. Despite the importance of belowground C sequestration in determining the net C sink potential of bioenergy, belowground C cycling processes in bioenergy crops remains largely uncharacterized. This study seeks to quantify and characterize the response of belowground C pools and fluxes to farm management scenarios (nitrogen (N) fertilization, stand age, and genotype) in two crops proposed as potential sources of bioenergy, Miscanthus x giganteus (Miscanthus) and Sorghum bicolor (Sorghum). This study additionally seeks to compare the belowground C fluxes in two crop species and draw conclusions about the potential for belowground C storage to mitigate carbon dioxide (CO2) emissions associated with the production and combustion of bioenergy derived from these two crop species. We quantified fine root biomass, soil organic carbon (SOC) content, and CO2 emissions associated with root respiration under five nitrogen (N) fertilization levels in Miscanthus and Sorghum. For perennial Miscanthus, we also quantified fine root biomass and root respiration among stands established over three different years to observe how the net belowground C flux changed over time and as a function of establishment year. Both fine root biomass and root respiration rates did not change as a function of fertilization in Sorghum stands, but SOC content in Sorghum was significantly greater in the <0.053 and 2-0.25mm size fractions in unfertilized stands compared to fertilized. In Miscanthus stands, N fertilization did not affect SOC content. Nitrogen fertilization decreased the belowground C storage capacity of Miscanthus by depressing fine root biomass. Simultaneously, N fertilization increased mass-specific rates of root respiration rates in Miscanthus. Despite increased mass-specific root respiration with N fertilizer addition, Miscanthus plot-scale root respiration did not change with increasing N application due to decreased fine root biomass observed with increasing amounts of N fertilization. Fine root biomass was six-fold greater in Miscanthus stands than Sorghum, while mass-specific root respiration rates were lower in Miscanthus stands than Sorghum. When scaled up, plot-scale root respiration emissions were lower in Miscanthus compared to Sorghum stands, while SOC content was greater in Miscanthus stands than Sorghum stands. Our results indicate Miscanthus has greater C sink potential than Sorghum via C allocated belowground to fine root biomass production and lower rates of root respiration.

Now that the EU and Sweden have adopted a new climate policy framework to regulate net carbon emission. A new concept, negative CO2 emission, has been considered to neutralize the CO2 generated from necessary consumption of fossil fuel. Biochar, as a pyrolytic product from biomass, can store carbon in a relatively stable way. Therefore, it is one of the most promising and outstanding tools for carbon sink. Biochar stability, defined as the ratio of remaining carbon in biochar after 100 years, is the most crucial factor when using biochar for carbon storage. So far, various approaches have been proposed to measure and predict biochar stability, such as elemental analysis, proximate analysis, accelerating aging methods. Each method has its pros and cons. The reliability of these methods still needs to be verified. In this project, the chemical accelerating aging method has been selected for assessing biochar stability, because this method captures both chemical and physical properties of biochar. Besides, the gas, liquid, and solid products generalized during the chemical treatment are collected and analyzed separately in order to study the oxidation mechanism. Biochar in this project is produced from miscanthus and seaweed at various pyrolysis temperature. It is found that biochar stability can be increased by enhancing pyrolysis temperature, and miscanthus biochar is more sensitive to pyrolysis temperature within the pyrolysis temperature range of 350-600℃. The highest biochar stability (73%) has been achieved with miscanthus-derived biochar produced at 550 ℃, which demonstrates high potential as carbon sequestration tool. / Nu när EU och Sverige har antagit en ny klimatpolitisk ram för att reglera nettokoldioxidutsläppen. Ett nytt koncept, negativt koldioxidutsläpp, har ansetts neutralisera den koldioxid som genereras av nödvändig förbrukning av fossila bränslen. Biokol, som en pyrolytisk produkt från biomassa, kan lagra kol på ett relativt stabilt sätt. Därför är det en av de mest lovande och enastående verktyg för kolsänka. Biokolsstabilitet, definierad som förhållandet mellan återstående kol i biokol efter 100 år, är den viktigaste faktorn vid användning av biokol för kollagring. Hittills har olika metoder föreslagits för att mäta och förutsäga biokolsstabilitet, såsom elementär analys, proximate analys, accelererande åldrande metoder. Varje metod har sina för-och nackdelar. Tillförlitligheten hos dessa metoder måste fortfarande kontrolleras. I detta projekt har den kemiska accelererande åldrandemetoden valts ut för att bedöma biokolsstabilitet, eftersom denna metod fångar upp både kemiska och fysikaliska egenskaper hos biokol. Förutom, gasen, flytande, och fasta produkter generaliserade under den kemiska behandlingen samlas in och analyseras separat för att studera oxidation mekanism. Biokol i detta projekt framställs av miscanthus och tång vid olika pyrolystemperatur. Det visar sig att biokolsstabiliteten kan ökas genom att öka pyrolystemperaturen, och miscanthusbiokol är mer känsligt för pyrolystemperatur inom pyrolystemperaturområdet 350-600°C. Den högsta biokolsstabiliteten (73%) har uppnåtts medbiokol som framställts vid 550°C och som visar stor potential som kolbindningsverktyg.

Forests play an important role in mitigating climate change. It can not only provide carbon sequestration in standing forests and long-life forest products, but can also reduce carbon release by bioenergy’s substitution of fossil fuel. Therefore, a comprehensive impact from forest carbon on landowners’ forest management decisions should be analyzed when considering those uncertainties in carbon life cycle. The first part of the dissertation is a meta-analysis review, in which important factors that can influence the estimation of harvesting rotations under carbon sequestration are summarized and analyzed. It concludes that some issues as natural disturbances and forest bioenergy deserve more attentions, which are addressed in the following two chapters. The second part adopts a revised Faustmann model to assess the relation between wildfire risk and prescribed fire under four assumed carbon policy scenarios. It arrives at the conclusion that penalty on carbon release in prescribed fire may reduce carbon sequestration in standing forests and make forest landowners to take the risk of loss in wildfire. Thus, a carbon policy with such a regulation should be adopted with caution. The third part investigates the probable influence brought by wood-based biofuel of stochastic prices with a Monte Carlo method. The results demonstrate that the assumption of double stochastic prices leads to earlier harvesting when comparing to constant price scenario or stochastic price assumption of only timber. The stochasticity of energy price may benefit landowners but also introduce uncertainties into their revenue. It also reduces sequestered carbon in standing forests and long-life forest products, which should be paid more attention when a general point of view on forest carbon is the concern. This project is informative for landowners who are facing new opportunities and challenges in forest management and is also helpful for carbon policy makers when dealing with forest carbon dilemmas of prescribed fire and bioenergy.

Belowground competition presents a threat to the production and sustainability of tree-grass ecosystems. Management scenarios designed to optimize the spatial and temporal distribution of soil resources will improve resource-use efficiency and promote greater co-production. We conducted three experiments to assess competition dynamics between loblolly pine and switchgrass. In a three-year field trial, loblolly pine and switchgrass were intercropped across varying competitive intensities. Interspecific competition decreased loblolly pine annual growth; however, establishing vegetation exclusion zones surrounding pines largely mitigated these effects. Switchgrass yields were less affected by interspecific competition compared to pines and land equivalency ratios indicated that with proper management co-production yields may exceed those of switchgrass monoculture. Switchgrass was a constant and significant competitor across all years while loblolly pine resource use was minimal in year 1 but increased in subsequent years. In a short-term greenhouse experiment, native soil was amended with biochar and inorganic N fertilizer and the effects of these amendments upon soil properties and switchgrass productivity were assessed. Biochar increased soil pH, total soil carbon, and soil moisture. However, N fertilization had negligible effects upon soil properties. Plant response to biochar was neutral to negative while N fertilization increased switchgrass foliar biomass but no interactive effects of the amendments were observed. Although the effects of biochar upon switchgrass production were trivial, its positive influence upon soil properties suggests a potential for mitigating competitive interactions. Finally, a field-scale study examined co-production of loblolly pine and switchgrass over two years in response to competition control, biochar, and N fertilizer. As expected, interspecific competition reduced soil resources and decreased plant productivity. Biochar increased total soil C and soil moisture levels but had relatively minor impacts upon other aspects of soil fertility or plant production. Nitrogen fertilization acidified soil pH and decreased total soil C and N but positively affected loblolly pine foliar N concentrations and switchgrass yields. A positive association between soil inorganic N and switchgrass yield suggests the species competitive influence may be increased with greater N supply.