With greenhouse gas emissions (of which CO2 is the major component) being a major environmental concern, mitigation of those emissions is becoming increasingly imperative. The ability to use a fast growing, photosynthetic organism like microalgae that can survive primarily on nutrients such as sunlight and air (with increased CO2 levels) makes it a desirable agent for CO2 sequestration. The primary goal of this project is the engineering of the sequestration of CO2 using the cultivation of the microalgae species <i>Chlorella vulgaris</i>. Secondary goals of the project are the exploration and development of valuable by-products of the cultivation and the determination of whether utilizing microalgae to capture CO2 could be integrated economically into an industrial facility.<p> The batch growth kinetics of the photosynthetic algal species <i>C. vulgaris</i> were investigated using a well-mixed stirred bioreactor. The growth rate was found to increase as the dissolved CO2 increased to 150 mg/L (10% CO2 by volume in the gas), but fell dramatically at higher concentrations. Increasing the radiant flux also increased growth rate. With a radiant flux of 32.3 mW falling directly on the 500 mL culture media, the growth rate reached up to 3.6 mg of cells/L-h. Both pH variation (5.5 - 7.0) and mass transfer rate of CO2 (KLa between 6 h-1 and 17 h-1) had little effect on growth rate.<p> The operation of continuously stirred tank bioreactors (CSTBs) at minimum cost is a major concern for operators. In this work, a CSTB design strategy is presented where impeller stirring speed and aeration rate are optimized to meet the oxygen demand of growing cells, simultaneously minimizing the capital and operating cost. The effect of microbial species, ions in the culture medium, impeller style, as well as changing CSTB size and biomass input density on the optimum operating conditions, is examined. A study of the effects of various parameters on the CSTB design is shown.<p> Using the kinetic data collected in the batch growth study, a novel external loop airlift photobioreactor (ELAPB) was designed and tested. A model was developed for <i>C. vulgaris</i> growth in the ELAPB that incorporated growth behaviour, light attenuation, mass transfer, and fluid dynamics. The model predicts biomass accumulation, light penetration, and transient CO2 concentrations, and compares predictions to experimental data for radiant fluxes of 0.075 1.15 W/m2 and 0 20% CO2 enrichment of feed air, with a 10% average error. The effect of radiant flux and CO2 concentration is presented with discussion of radial and vertical profiles along the column. For a fed-batch culture at a biomass density of 170 mg/L, the penetration of the radiant flux was found to decrease by 50% within the first 1 cm, and 75% at 2 cm. Theoretical optimum growth conditions are determined to be 0.30 W/m2 and 6% CO2 enrichment of inlet feed air.<p> The algal culture was observed to be a workable electron acceptor in a cathodic half cell. A net potential difference of 70 mV was achieved between the growing <i>C. vulgaris</i> culture acting as a cathode and a 0.02 M potassium ferrocyanide anodic half cell. Surge current and power levels of 1.0 µA/mg of cell dry weight and 2.7 mW/m2 of cathode surface area were measured between these two half cells. The recently developed photosynthetic cathode was also coupled to a fermentative anode to produce a completely microbial fuel cell. Loading effects and the effect of changing culture conditions on fuel cell operation are reported. The maximum power output measured was 0.95 mW/ m2 at 90 V and 5000 ohms. A significant increase in this output is achieved with the addition of supplemental glucose to the anodic half cell and the enrichment of the feed air bubbled into the cathodic half cell with 10% CO2.<p> Two economic feasibility studies were performed on the integration of ELAPBs into an industrial facility. These integration studies operated the ELAPBs continuously as biocathodes in coupled microbial fuel cells (MFCs) that capture CO2 from an existing 130 million L/yr bioethanol plant, while generating electrical power and yielding oil for biodiesel to provide operational revenue to offset costs. The anodes for the coupled MFCs are the existing yeast batch fermentors, and the CO2 to be sequestered comes from the existing bioethanol production. Two different design schemes were evaluated, in both cases the maximum profit was achieved with the maximum number of tall columns operated in parallel. The first design evaluated a batch bioethanol facility with off-site oil processing, and the economic feasibility is demonstrated by the positive Net Present Worth achieved over the 20 year life of the plant, at a 10% rate of return on investment. The second design, for a continuous bioethanol operation, processes both oil and algae biomass on-site, but the economics of this second process are only positive (Internal Rate of Return 9.93%.) if the government provides financial assistance in the form of generous carbon credits (a speculative $100 per tonne of CO2 not yet attained) and a 25% capital equipment grant.

Liquid transportation fuels can be produced by gasification of carbon containing biomass to syngas( a gaseous mixture of CO and H2) with subsequent conversion of the syngas to fuels. One possible process is the so called mixed alcohols synthesis, which produces a mixture of ethanol and higher alcohols. Another possible process is the reaction of syngas to Fischer-Tropsch liquids, mainly diesel fuel. This study examines the economics of syngas, ethanol and diesel fuel production from lignocellulosic biomass (southern pine residues). The process is modeled with Aspen Plus, a process simulation software package. The process is simulated for plant sizes between 715 and 2205 dry tons/day. The feedstock moisture content is varied between 20% and 50% and the feedstock costs are varied between $30/dry ton and $80/dry ton. The influences of the examined variables on the minimum product selling price are determined. The economic effects of an integration of the mixed alcohols and the FT diesel process with a kraft mill are also evaluated.

Orientador: Pedro de Oliva Neto / Resumo: Desejando ao final do trabalho obter um bioprocesso integrado usando palha de cana-de-açúcar (PC), este trabalho teve início com a utilização desse substrato para produção de enzimas fribrolíticas, xilanases e celulases, em culturas axênicas, incluindo espécies de Trichoderma e Aspergillus. A triagem para o melhor produtor foi realizada em “shaker” em fermentação submersa. A cultura do fungo T. reesei QM9414 alcançou a melhor produção de enzimas, e em tanque agitado, utilizando um biorreator de 3 L, mostrou o mesmo perfil de produção (~90 U/mL, 0.6 FPU/mL para xilanase e celulases, respectivamente). Em relação a este resultado, a produção de enzimas para as misturas binárias e ternárias destes fungos foi menor, sendo que a melhor combinação, T. reesei QM 9414+A. fumigatus M51, alcançou 60 U/mL e 0.08 FPU/mL respectivamente. Com intuito de otimizar a produção de enzimas utilizando um mix de substratos: palha de cana, como principal componente, e o farelo de trigo e a polpa cítrica, como supostos indutores de atividade enzimática, foi realizado um delineamento de misturas do tipo D-optimal. O resultado da otimização da mistura dos substratos mostrou que o trigo e a polpa cítrica não tiveram um efeito indutivo na produção das enzimas tendo a palha de cana como principal substrato. A enzima xilanase foi caracterizada em seu pH e temperatura ótimos (pH 5, e 50 ºC respectivamente), bem como a estabilidade da enzima nestes parâmetros. Alguns íons e EDTA foram aplicados para determin... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In order to obtain an integrated bioprocess using Sugarcane Straw (SS), this work began with the use of this substrate for the fibrolytic enzymes production, xylanases and cellulases, in axenic fungal cultures, including Trichoderma and Aspergillus species. The screening for the best producer was performed in shaker under submerged fermentation. The T. reesei QM9414 culture achieved the best enzyme production, and in a stirred tank using a 3 L bioreactor showed the same production profile (~90 U/mL and 0.6 FPU/mL for xylanase and cellulase, respectively). Regarding this result, the enzyme production by binary and ternary mixtures of these fungi was lower, as example the best combination T. reesei QM 9414+A. fumigatus M51, reached 60 U/mL and 0.08 FPU/mL, respectively. Aiming optimize the enzyme production by a mix of substrates using SS as the main substrate, and wheat bran and citrus pulp as supposed enzyme inductors, a D-optimal mixture design was performed. The mixture substrates optimization showed that wheat bran and citrus pulp did not have an inductive effect on the enzymes production. The enzyme xylanase was characterized by its optimal pH and temperature (pH 5 and 50 ºC, respectively, as well as the stability of the enzyme in these parameters. Some ions and EDTA were applied to determine the xylanase stability under these conditions, and the ion Mn2+ was the best inductor, 49% (10 mM). The extract containing xylanases, produced under previous optimized conditions was... (Complete abstract click electronic access below) / Doutor

Over recent years microbial oil has attracted much attention due to its potential to replace traditional oil sources in the production of biofuels and nutraceuticals. Its advantages arise from its independence of the food supply chain and its ease of production compared to conventional plant oils. Also, as concerns for the environment grow, microbially-synthesized oil emerges as potential competitor for the sustainable production of biodiesel. However, the high cost of its production currently hinders its large scale application. The bottlenecks to industrial microbial oil production are the cost of substrate and cultivation. Current research is focusing on process improvements to make microbial oil more competitive and worthwhile to produce. Several types of microorganisms have been explored so far and waste substrates have been utilised as cheap feedstocks. The overall cost is affected by the fermentation stage, therefore it is imperative to design cultivations with little operating requirements and high yields. Consequently, the present thesis aims to contribute to the field by developing and investigating a simple process for oleaginous yeast cultivation, focusing mainly on enhancing the yields during the bioreactor stage. Oleaginous yeasts were screened for their ability to grow on glycerol and the most promising strain was selected for further research. Then, the necessary conditions for its growth and oil accumulation were defined. Shake-flask cultivations showed that the specific growth rate and glycerol consumption of Rh. glutinis were higher at lower glycerol concentrations (smaller or equal to40 g/L), while higher C/N elemental ratios enhanced oil content. Experimental data were used to construct an unstructured kinetic model to describe and predict the system's behaviour. The Monod-based model took into account double substrate growth dependence and substrate inhibition. Following that, bioreactor cultivations extended the range of parameters studied, to include the influence of aeration rate and oxygen supply on cellular growth and microbial oil production. Cultivations at different air flow rates were performed in a 2 L bioreactor and showed that a low aeration rate of 0.5 L/min gave the best glycerol and nitrogen uptake rates, resulting in a concentration of biomass of 5.3 g/L with oil content of 33% under simple batch operation. This was improved by 68% to 16.8 g/L (cellular biomass) with similar oil content (34%) by applying a fed-batch strategy. Finally, different glycerol feeding schemes were evaluated in terms of their effect on oil accumulation. The concept of targeting first a cell proliferation stage, limited by the availability of nitrogen, followed by a lipid accumulation stage, fuelled by glycerol was tested. Continual feeding and pulsed feedings, delivering the same total amount of nitrogen (and glycerol), resulted in similar elevated values of both cellular biomass (~25 g/L) and oil content (~40%). Addition of glycerol at higher rates but giving the same total amount of nitrogen led to a further increase in oil content to 53%, resulting in an overall oil yield of more than 16 g/L (the highest achieved throughout the project). With comparable yields to those reported in the literature but achieved with a much poorer medium, there is every reason to be optimistic that microbial oil production from glycerol could be commercially viable in the future.

Alguns conceitos de biorrefinarias estão baseados em processos termoquímicos, sendo a pirólise rápida um dos mais promissores desses processos. Os produtos da pirólise rápida são: o bio-óleo, gases combustíveis e carvão, sendo a distribuição típica de 50:30:20 em base mássica. O bio-óleo é o principal produto, e pode ser diretamente usado como combustível, ou pós-processados para a obtenção de químicos de maior valor agregado. O aquecimento com micro-ondas, amplamente empregado na química verde, começa a ser estudado como uma alternativa de aquecimento. Entretanto os rendimentos alcançados em bio-óleo são inferiores aos obtidos pela pirólise rápida convencional, devido essencialmente às suas baixas taxas de aquecimento. Para resolver esse problema esta tese está propondo a utilização de absorvedores de micro-ondas para auxiliar no processo de aquecimento, e também permitir a alimentação semi-contínua e contínua de biomassa ao processo. O uso de leito fluidizado e catalisadores pode ser integrado a esse conceito. As condições de pirólise-rápida são alcançadas devido ao aumento da taxa de aquecimento da biomassa, que passa a ser aquecida de forma híbrida pelo mecanismo de condução de calor através das partículas de absorvedores de micro-ondas aquecidos, e diretamente através do aquecimento dielétrico por micro-ondas. O aumento das taxas de aquecimento resulta em maiores velocidades de reação, possibilitando um aumento de rendimento em bio-óleo. Esse conceito foi testado experimentalmente em uma unidade em escala de bancada para o processamento de biomassas residuais e microalgas, usando carbeto de silício (SiC) como absorvedor de micro-ondas. Foram verificadas elevadas taxas de aquecimento, sendo a biomassa aquecida e os voláteis removidos do reator quase instantaneamente. Foram obtidos 65% e 64% em rendimentos de bio-óleo para a serragem de madeira e farelo de sabugo de milho, respectivamente. O mesmo sistema foi utilizado para testar a pirólise rápida catalítica. Microalgas foram processadas com e sem a presença de HZSM-5. Rendimentos de 57% e 59% em bio-óleo foram alcançados para Chlorella sp. e Nannochloropsis, respectivamente. Verificaram-se maiores rendimentos comparados com a literatura. Esses resultados indicam que o conceito de pirólise rápida com aquecimento por micro-ondas é tecnicamente viável, necessitando de estudos complementares para evidenciar a sua viabilidade econômica. / Some concepts of biorefineries are based on thermochemical processes and fast pyrolysis is one of the most promising of these processes. The fast pyrolysis products are biooil, fuel gas and char, with typical distribution of 50:30:20 in weight basis. The bio-oil is the main product, and it can be directly used as fuel, or post-processed in order to obtain higher value added chemicals. The microwave heating, widely used in green chemistry, begins to be studied as an alternative heating. However the yields achieved in bio-oil are lower than those obtained by the conventional fast pyrolysis, mainly due to its low heating rates. To solve this problem this thesis is proposing the use of microwave absorbers to improve the heating process, and that also allow semi-continuous and continuous feeding of biomass to the process. The use of fluidized bed and catalysts can be integrated into this concept. The fast pyrolysis conditions are achieved due to increased heating rate of biomass, which becomes heated in a hybrid way by heat conduction mechanism from heated microwave absorbers, and directly through the dielectric heating from microwaves. The increase in heating rates results in higher reaction rates, allowing higher yields of bio-oil. This concept has been experimentally tested in a bench scale unit for processing waste biomass and microalgae using silicon carbide (SiC) as a microwave absorber. High heating rates were observed, the heated biomass and the volatiles were removed from the reactor almost instantaneously. A maximum bio-oil yield of 65% and 64% was obtained for wood sawdust and corn stover, respectively. The same system was used to test the catalytic fast pyrolysis. Microalgae were processed with and without the presence of HZSM-5. Yields of 57% and 59% of bio-oil were achieved for Chlorella sp. and Nannochloropsis, respectively. Higher yields of bio-oil were observed compared to the literature. These results suggest that the concept of fast microwave-assisted pyrolysis is technically feasible, requiring further studies to demonstrate its economic viability.

Made available in DSpace on 2016-06-02T19:56:52Z (GMT). No. of bitstreams: 1 5473.pdf: 3094891 bytes, checksum: 057207774d6a2325d5d17dd8ddc1fa38 (MD5) Previous issue date: 2013-07-26 / The ethanol (fuel grade and anhydrous) is, fundamentally, the most relevant global biofuel nowadays, in energy, environmental, economic and technological terms. This scenario brings up the Brazilian ethanol, made from sugarcane, a very studied topic. Thus, knowing the process of ethanol production from sugarcane in technical terms shows itself as a relevant fact, since it can contribute to the increase of production plants profits. Notoriously, the acquaintance and analysis of some project s economic viability can greatly optimize the intended returns, while it can be taken as tool for decision making. Therefore, the present work aimed, in the technical side, the improvement of the computational model (developed with EMSO software) capable of simulating ethanol plants (first and second generations 1G and 2G, respectively) by the input of realistic data, obtained from actual operating ethanol plants. In the economic aspect, the simulations production data were used to feed the economic viability analysis, using the IRR (internal return rate) and NPV (net present value) concepts. Thereby, three cases were considered: 1) plant producing 1G ethanol and electric energy surplus (plant A); 2) plant producing 1G and 2G ethanol, no electric energy surplus (plant B) and 3) plant producing 1G ethanol and: either 2G ethanol or electric energy surplus (plant C). One obtained the following: IRRA = 7.6% and NPVA = - USD 34,5M; IRRB = 8,3% and NPVB = - USD 30,0M; IRRC = 8,0% and NPVC = - USD 41,8M. So, from that, one concludes that the methodology, the software and the biorefinery model were useful and adequate for the projected analysis. In comparison with the minimum acceptable rate of return (MARR, 11% in this case), none of the scenarios were acceptable (IRRs < MARR), which is ratified by the negative NPVs (all). None of the simulated plants were considered economic viable, being plant B the most attractive among the three cases, under the given conditions and assumptions. / O etanol (carburante e anidro) é, fundamentalmente, o biocombustível de maior relevância global na atualidade, tanto em termos energéticos, ambientais, econômicos, como em termos tecnológicos. Neste panorama encontra-se o etanol brasileiro, oriundo da cana-deaçúcar, muito estudado na atualidade. Dessa maneira, conhecer o processo de sua obtenção, em termos técnicos, a partir da cana, mostra-se relevante, pois pode contribuir para a geração de expressivos ganhos econômicos para as unidades produtoras. Notoriamente, o conhecimento e análise da viabilidade econômica de um dado projeto pode otimizar sobremaneira os retornos pretendidos, ao passo que serve como ferramenta de aceitação ou rejeição do mesmo. Assim, o trabalho objetivou, no quesito técnico, o aperfeiçoamento da aderência de um modelo computacional, criado com software EMSO, simulador de plantas de etanol (primeira e segunda gerações 1G e 2G, respectivamente), através da inserção de dados realísticos advindos de plantas reais em operação. No lado econômico, utilizaram-se os dados de produção gerados pela simulação para alimentar uma análise de viabilidade econômica, através dos conceitos de TIR (taxa interna de retorno) e VPL (valor presente líquido). Portanto, três casos foram estudados: 1) planta produtora de etanol 1G e cogeradora de energia elétrica excedente (planta A); 2) planta produtora de etanol 1G e 2G, sem cogeração excedente (planta B) e 3) planta produtora de etanol 1G e: ou etanol 2G ou energia elétrica cogerada (planta C). Obtiveram-se: TIRA = 7,6% e VPLA = - USD 34,5M; TIRB = 8,3% e VPLB = - USD 30,0M; TIRC = 8,0% e VPLC = - USD 41,8M. Concluiu-se que metodologia, o software e o modelo de biorrefinaria adotados foram úteis e adequados para a análise pretendida. Comparando-se com a TMA (taxa mínima de atratividade) (11%) utilizada, todos os projetos são inviáveis (TIRs < TMA), o que é corroborado pelos VPLs serem, todos, negativos. Nenhuma das plantas simuladas mostrou-se economicamente viável, sendo a planta B a mais atrativa entre as três, sob as premissas e condições adotadas.

The use of carbon from fossil-based resources result in changes in the earth’s climate due to emissions of greenhouse gases. Biomass is the only renewable source of carbon that may be converted to transportation fuels and chemicals, markets now fully dominated by traditional oil supply. The biorefinery concept for upgrading and refinement of biomass feedstocks to value-added end-products has the potential to mitigate greenhouse gas emissions and replace fossil products. Most biorefineries use biochemical conversion processes and may have by-product streams suitable as feedstocks for thermal conversion and production of syngas. Further synthesis to value-added products from the syngas could increase the product output from the biorefinery. The application of thermal conversion processes integrated into an existing biorefinery concept has been evaluated in this licentiate thesis work. Two by-product streams; hydrolysis (lignin) residue from an ethanol plant and biogas from wastewater treatment, have been investigated as gasification/reforming feedstocks. Also, the pre-treatment method torrefaction has been evaluated for improved gasification fuel characteristics and integration aspects. A new process and system concept (Bio2Fuels) with potential carbon negative benefits has been suggested and evaluated as an alternative route for syngas production by separating biomass into a hydrogen rich gas and a carbon rich char product. The evaluation demonstrated that hydrolysis residue proved a suitable feedstock for gasification with respect to syngas composition. Biogas can be further reformed to syngas by combined biomass gasification and methane reforming, with promising results on CH4 conversion rate and increased H2/CO ratio at temperatures ≥1000°C. The pre-treatment method torrefaction was demonstrated to improve fuel qualities and may thus significantly facilitate entrained flow gasification of biomass residue streams. Also, integration of a torrefaction plant at a biorefinery site could make use of excess heat for drying the raw material before torrefaction. The Bio2Fuels concept was evaluated and found feasible for further studies. The application of thermal conversion processes into an existing biorefinery, making use of by-products and biomass residues as feedstocks, has significant potential for energy integration, increased product output as well as for climate change mitigation.

Alguns conceitos de biorrefinarias estão baseados em processos termoquímicos, sendo a pirólise rápida um dos mais promissores desses processos. Os produtos da pirólise rápida são: o bio-óleo, gases combustíveis e carvão, sendo a distribuição típica de 50:30:20 em base mássica. O bio-óleo é o principal produto, e pode ser diretamente usado como combustível, ou pós-processados para a obtenção de químicos de maior valor agregado. O aquecimento com micro-ondas, amplamente empregado na química verde, começa a ser estudado como uma alternativa de aquecimento. Entretanto os rendimentos alcançados em bio-óleo são inferiores aos obtidos pela pirólise rápida convencional, devido essencialmente às suas baixas taxas de aquecimento. Para resolver esse problema esta tese está propondo a utilização de absorvedores de micro-ondas para auxiliar no processo de aquecimento, e também permitir a alimentação semi-contínua e contínua de biomassa ao processo. O uso de leito fluidizado e catalisadores pode ser integrado a esse conceito. As condições de pirólise-rápida são alcançadas devido ao aumento da taxa de aquecimento da biomassa, que passa a ser aquecida de forma híbrida pelo mecanismo de condução de calor através das partículas de absorvedores de micro-ondas aquecidos, e diretamente através do aquecimento dielétrico por micro-ondas. O aumento das taxas de aquecimento resulta em maiores velocidades de reação, possibilitando um aumento de rendimento em bio-óleo. Esse conceito foi testado experimentalmente em uma unidade em escala de bancada para o processamento de biomassas residuais e microalgas, usando carbeto de silício (SiC) como absorvedor de micro-ondas. Foram verificadas elevadas taxas de aquecimento, sendo a biomassa aquecida e os voláteis removidos do reator quase instantaneamente. Foram obtidos 65% e 64% em rendimentos de bio-óleo para a serragem de madeira e farelo de sabugo de milho, respectivamente. O mesmo sistema foi utilizado para testar a pirólise rápida catalítica. Microalgas foram processadas com e sem a presença de HZSM-5. Rendimentos de 57% e 59% em bio-óleo foram alcançados para Chlorella sp. e Nannochloropsis, respectivamente. Verificaram-se maiores rendimentos comparados com a literatura. Esses resultados indicam que o conceito de pirólise rápida com aquecimento por micro-ondas é tecnicamente viável, necessitando de estudos complementares para evidenciar a sua viabilidade econômica. / Some concepts of biorefineries are based on thermochemical processes and fast pyrolysis is one of the most promising of these processes. The fast pyrolysis products are biooil, fuel gas and char, with typical distribution of 50:30:20 in weight basis. The bio-oil is the main product, and it can be directly used as fuel, or post-processed in order to obtain higher value added chemicals. The microwave heating, widely used in green chemistry, begins to be studied as an alternative heating. However the yields achieved in bio-oil are lower than those obtained by the conventional fast pyrolysis, mainly due to its low heating rates. To solve this problem this thesis is proposing the use of microwave absorbers to improve the heating process, and that also allow semi-continuous and continuous feeding of biomass to the process. The use of fluidized bed and catalysts can be integrated into this concept. The fast pyrolysis conditions are achieved due to increased heating rate of biomass, which becomes heated in a hybrid way by heat conduction mechanism from heated microwave absorbers, and directly through the dielectric heating from microwaves. The increase in heating rates results in higher reaction rates, allowing higher yields of bio-oil. This concept has been experimentally tested in a bench scale unit for processing waste biomass and microalgae using silicon carbide (SiC) as a microwave absorber. High heating rates were observed, the heated biomass and the volatiles were removed from the reactor almost instantaneously. A maximum bio-oil yield of 65% and 64% was obtained for wood sawdust and corn stover, respectively. The same system was used to test the catalytic fast pyrolysis. Microalgae were processed with and without the presence of HZSM-5. Yields of 57% and 59% of bio-oil were achieved for Chlorella sp. and Nannochloropsis, respectively. Higher yields of bio-oil were observed compared to the literature. These results suggest that the concept of fast microwave-assisted pyrolysis is technically feasible, requiring further studies to demonstrate its economic viability.

Nas últimas décadas observou-se tanto o crescimento das preocupações ambientais e de sustentabilidade. Neste contexto, surgiu o conceito de biorrefinaria. No Brasil, uma das principais lavouras agroindustriais é a produção de cana-de-açúcar. A indústria sucroalcooleira já atua como um modelo de biorrefinaria tendo a possibilidade de produção de açúcar de etanol e ainda de energia elétrica. Contudo, existe grande potencialidade de produtos de originários de biomassa vegetal. Alguns exemplos das potencialidades são: (i) a utilização dos açúcares da fração polissacarídica para produção de etanol; (ii) produção de polpa e papel; (iii) produção de nanomateriais entre outras. Assim, este trabalho se propõe a buscar e aplicar tecnologias e processos voltados a utilização da cana-de-açúcar para a obtenção de produtos variados. O primeiro processo utilizado é a separação das frações casca e miolo da cana-de-açúcar: na casca existe uma baixa quantidade de células de armazenamento de açúcar e uma maior proporção de fibras estruturais ademais, da epiderme extrai-se a cera; na fração miolo concentra-se a maior parte do caldo rico em sacarose, pela elevada quantidade de células de parênquima. Visando elevar a concentração de sacarídeos para a produção de etanol estudou-se a realização de um processo hidrotérmico usando o próprio suco da cana-de-açúcar para a extração de açúcares da fração de hemiceluloses. Observou-se que para a reação hidrotérmica em meio neutro na faixa de temperaturas estudada (110 a 130°C) cerca de 95% dos sacarídeos são conservados. Contudo, nestas condições reacionais a preservação de massa de hemiceluloses também se mantém nesta faixa, assim verificou-se que o uso de um catalizador ácido permitiria uma conservação de sacarídeos similar e aceleraria a reação de remoção de hemiceluloses. Usando processos similares aos usados na indústria de papel e celulose obteve-se dois materiais celulósicos das frações casca e miolo de cana-de-açúcar com características físico-mecânicas diferenciadas. Apesar do maior teor de células de parênquima no miolo original, observou-se que o papel desta fração apresentou resultados promissores com propriedades similares ao de papeis comerciais. A partir destas polpas, obteve-se dois materiais celulósicos nanofibrilados distintos, sendo o material da casca dúctil e o de miolo mais rígido (maior módulo de Young) e ao mesmo tempo mais frágil (menor alongamento para a ruptura). Verificou-se ainda que a partir dessas polpas celulósicas pode-se produzir nanocristais de celulose II usando um processo de hidrólise e solubilização com ácido sulfúrico seguido de reprecipitação. Desenvolveu-se o processo de produção de nanocristais de celulose I usando água subcrítica associado ou não a CO2. Este processo tem o potencial de substituir a atual produção de nanocristais de celulose visto que neste utiliza-se somente água (com ou sem CO2) para promover a hidrólise em oposição ao método clássico que usa elevadas concentrações de ácido sulfúrico permitindo uma economia financeira e produzindo menor volume de resíduos. / In the last decades environmental concerns and sustainability have grown. In this context, the biorefinery concept arose. In Brazil, one of the leading agro-industrial crops is the production of sugarcane. The sugar industry is already a model of a biorefinery because of the possibility of producing ethanol, sugar and even electricity. However, plant biomass still has a great potential to produce new materials and chemicals. Some of the capabilities are: (i) the use of the sugars from the polysaccharide fraction aiming the ethanol production; (ii) the production of pulp and paper; (iii) production of nanomaterials, among others. This work aims to seek and apply technologies and processes to obtain different products from sugarcane. The first used is the separation of the rind and core fractions of sugarcane: in the rind there is a low amount of sugar storage cells and a higher proportion of structural fibers, and also wax from the epidermis; the core fraction concentrates the majority of the sucrose rich broth as consequence of the high quantity of parenchyma cells. In order to increase the concentration of saccharides a hydrothermal process was studied using the own juice of sugar cane to extract sugars from the hemicellulose fraction. It was observed that for the hydrothermal reaction in neutral medium in the temperature range studied (110 to 130 °C) of about 95% saccharides are conserved. However, in these reaction conditions the hemicellulose preservation is also kept in this range, so it was found that the use of an acid catalyst allow similar saccharides recovery and accelerate the hemicellulose removal. Using similar procedures to those of the pulp and paper industry two cellulosic materials with differentiated physical and mechanical characteristics were obtained from the rind and core fractions of sugarcane. Although most parenchyma content in the original core material, it was observed that this fraction showed promising results with properties similar to commercial papers. From these pulps, two different nanofibrillated cellulosic materials were obtained, being the rind material a ductile material and the core a rigid (higher Young\'s modulus) and brittle (lower elongation at break) one. It was also found that from these pulps cellulose II nanocrystals can be produced using a process of hydrolysis and solubilization with sulfuric acid followed by a reprecipitation process. The production of cellulose I nanocrystals through processes using subcritical water with or without CO2 were developed. These processes have the potential to replace the current nanocrystals production since only water is used (with or without CO2) to promote the hydrolysis, compared to the traditional method, which uses high concentrations of sulfuric acid, thus enabling economical saves and producing less amount of wastes.

Alguns conceitos de biorrefinarias estão baseados em processos termoquímicos, sendo a pirólise rápida um dos mais promissores desses processos. Os produtos da pirólise rápida são: o bio-óleo, gases combustíveis e carvão, sendo a distribuição típica de 50:30:20 em base mássica. O bio-óleo é o principal produto, e pode ser diretamente usado como combustível, ou pós-processados para a obtenção de químicos de maior valor agregado. O aquecimento com micro-ondas, amplamente empregado na química verde, começa a ser estudado como uma alternativa de aquecimento. Entretanto os rendimentos alcançados em bio-óleo são inferiores aos obtidos pela pirólise rápida convencional, devido essencialmente às suas baixas taxas de aquecimento. Para resolver esse problema esta tese está propondo a utilização de absorvedores de micro-ondas para auxiliar no processo de aquecimento, e também permitir a alimentação semi-contínua e contínua de biomassa ao processo. O uso de leito fluidizado e catalisadores pode ser integrado a esse conceito. As condições de pirólise-rápida são alcançadas devido ao aumento da taxa de aquecimento da biomassa, que passa a ser aquecida de forma híbrida pelo mecanismo de condução de calor através das partículas de absorvedores de micro-ondas aquecidos, e diretamente através do aquecimento dielétrico por micro-ondas. O aumento das taxas de aquecimento resulta em maiores velocidades de reação, possibilitando um aumento de rendimento em bio-óleo. Esse conceito foi testado experimentalmente em uma unidade em escala de bancada para o processamento de biomassas residuais e microalgas, usando carbeto de silício (SiC) como absorvedor de micro-ondas. Foram verificadas elevadas taxas de aquecimento, sendo a biomassa aquecida e os voláteis removidos do reator quase instantaneamente. Foram obtidos 65% e 64% em rendimentos de bio-óleo para a serragem de madeira e farelo de sabugo de milho, respectivamente. O mesmo sistema foi utilizado para testar a pirólise rápida catalítica. Microalgas foram processadas com e sem a presença de HZSM-5. Rendimentos de 57% e 59% em bio-óleo foram alcançados para Chlorella sp. e Nannochloropsis, respectivamente. Verificaram-se maiores rendimentos comparados com a literatura. Esses resultados indicam que o conceito de pirólise rápida com aquecimento por micro-ondas é tecnicamente viável, necessitando de estudos complementares para evidenciar a sua viabilidade econômica. / Some concepts of biorefineries are based on thermochemical processes and fast pyrolysis is one of the most promising of these processes. The fast pyrolysis products are biooil, fuel gas and char, with typical distribution of 50:30:20 in weight basis. The bio-oil is the main product, and it can be directly used as fuel, or post-processed in order to obtain higher value added chemicals. The microwave heating, widely used in green chemistry, begins to be studied as an alternative heating. However the yields achieved in bio-oil are lower than those obtained by the conventional fast pyrolysis, mainly due to its low heating rates. To solve this problem this thesis is proposing the use of microwave absorbers to improve the heating process, and that also allow semi-continuous and continuous feeding of biomass to the process. The use of fluidized bed and catalysts can be integrated into this concept. The fast pyrolysis conditions are achieved due to increased heating rate of biomass, which becomes heated in a hybrid way by heat conduction mechanism from heated microwave absorbers, and directly through the dielectric heating from microwaves. The increase in heating rates results in higher reaction rates, allowing higher yields of bio-oil. This concept has been experimentally tested in a bench scale unit for processing waste biomass and microalgae using silicon carbide (SiC) as a microwave absorber. High heating rates were observed, the heated biomass and the volatiles were removed from the reactor almost instantaneously. A maximum bio-oil yield of 65% and 64% was obtained for wood sawdust and corn stover, respectively. The same system was used to test the catalytic fast pyrolysis. Microalgae were processed with and without the presence of HZSM-5. Yields of 57% and 59% of bio-oil were achieved for Chlorella sp. and Nannochloropsis, respectively. Higher yields of bio-oil were observed compared to the literature. These results suggest that the concept of fast microwave-assisted pyrolysis is technically feasible, requiring further studies to demonstrate its economic viability.