Dissertations / Theses on the topic 'Biomass pre-treatment'

This project was focussed on drying and feeding timber-yard waste for a gasifier and the assessment of the feedstock drying on the gasifier performance. This required a thermodynamic model to be developed in order to assess the effect of drying as was highlighted in the literature survey. A heat exchanger model was also developed which formed the basis for the design of the drier. The project aim was to develop a reliable feed process for a lab-scale gasifier that was able to dry the proposed feedstock to below 10%. The plant was to be as far as possible, automated, with minimal maintenance requirements.

Mestrado em Biotecnologia
O objetivo deste trabalho foi estudar o pré-tratamento de biomassa lignocelulósica, como a palha de trigo, usando líquidos iónicos (LIs) de modo a obter a separação dos principais componentes, nomeadamente, celulose, hemicelulose e lignina. O processo de pré-tratamento foi otimizado com base em duas metodologias descritas na literatura utilizando o líquido iónico acetato de 1-etil-3-metilimidazólio ([emim][CH3COO]). A metodologia otimizada permitiu separar as frações ricas em hidratos de carbono das frações de lignina, ambas com elevada pureza, e com uma recuperação de LIs até um máximo de 97% da sua massa inicial. Desta forma, o LI pode ser reusado confirmando a flexibilidade do processo desenvolvido. A versatilidade do método foi testada com a investigação de três líquidos iónicos diferentes, nomeadamente hidrogenossulfato de 1-butil-3-metilimidazólio ([bmim][HSO4]), tiocianato de 1-butil-3-metilimidazólio ([bmim][SCN]) e dicianamida de 1-butil-3-metilimidazólio ([bmim][N(CN)2]). No processo de dissolução de palha de trigo observou-se uma dissolução completa a nível macroscópico apenas para os líquidos iónicos [emim][CH3COO] e [bmim][HSO4]. O [emim][CH3COO] apresentou maior eficiência no processo de dissolução e regeneração da biomassa. Contrariamente, o [bmim][SCN] demonstrou ser o menos eficiente em todo o processo de pré-tratamento. Um comportamento diferente foi observado para o [bmim][HSO4], cujo pré-tratamento apresentou similaridades a uma hidrólise ácida. Os pré-tratamentos com [bmim][HSO4] e [bmim][N(CN)2] permitiram a obtenção de frações ricas em celulose com um conteúdo em hidratos de carbono de 87 a 90%. Para as frações ricas em celulose provenientes do pré-tratamento com [emim][CH3COO] foram efetuados ensaios de hidrólise enzimática para verificar a potencial aplicação destas frações, bem como, avaliar a eficiência das metodologias de pré-tratamento estudadas. Os resultados obtidos demonstraram elevado índice de digestibilidade da celulose e confirmou o elevado teor de glucose presente na fração celulósica obtida pela metodologia otimizada. A técnica de Espectroscopia de Infravermelho com Transformadas de Fourier (FT-IR) permitiu efetuar análises qualitativas e quantitativas de todas as amostras obtidas nos pré-tratamentos realizados. Para avaliar a pureza dos LIs após os pré-tratamentos utilizou-se a técnica espectroscópica de ressonância magnética nuclear (RMN). Os resultados provenientes dos ensaios de hidrólise enzimática foram obtidos através da técnica cromatográfica de HPLC.
This work is devoted to the pre-treatment of lignocellulosic biomass using ionic liquids (ILs) to separate cellulose, hemicellulose and lignin fractions. Particularly, research was focused on studying the influence of various ILs on the pre-treatment of wheat straw. The pre-treatment procedure was optimised basing on two methodologies presented in the literature. In the optimised method 1-ethyl-3-methylimidazolium acetate ([emim][CH3COO]) IL was used. The developed method is beneficial as allows a separation of highly-purified carbohydrate and lignin-rich samples and permits to recover ILs with a yield of 97wt%. Therefore, the IL could be reused confirming a great flexibility of the developed method. Furthermore, versatility of the method was confirmed by examination of different ILs such as 1-butyl-3-methylimidazolium hydrogensulfate ([bmim][HSO4]), 1-butyl-3-methylimidazolium thiocyanate ([bmim][SCN]) and 1-butyl-3-methylimidazolium dicyanamide ([bmim][N(CN)2]). Only [emim][CH3COO] and [bmim][HSO4] ILs were found to be capable to achieve a macroscopic complete dissolution of wheat straw. Considering dissolution and regeneration process, [emim][CH3COO] was the most efficient among investigated ILs. On the contrary, [bmim][SCN] demonstrated the lowest efficiency either in dissolution and regeneration or fractionation processes. The [bmim][HSO4] showed different behaviour from other ILs exhibiting similarities to acid hydrolysis pre-treatment. Pre-treatments with [bmim][HSO4] and [bmim][N(CN)2] allowed to recover cellulose rich-samples with a carbohydrate content between 87 to 90wt%. In order to verify the potential further applicability of obtained carbohydrate-rich fractions as well as to evaluate the pre-treatment efficiency, the cellulose-rich fraction obtained from treatment with [emim][CH3COO] was applied for the enzymatic hydrolysis. Achieved results showed a high digestibility of cellulose-rich samples and confirmed a high glucose yield for the optimised methodology. Qualitative and quantitative analyses of the pre-treatment with ILs were made using the Fourier-Transform Infrared Spectroscopy (FT-IR). The NMR analysis was used to evaluate the purity of ILs after pre-treatments. Results of enzymatic hydrolysis analysis were controlled by the HPLC.

A technique that is becoming more widespread in usage and popularity, ball milling has been used successfully in the pretreatment of sodium lignosulphonate (NaLS), a waste biomass material. The ball milled material produced higher yields of commercially valuable aromatic products, particularly vanillin in an industry standard copper-catalysed aerobic oxidation reaction. Through the optimisation of the parameters of this pretreatment technique both for NaLS alone and NaLS with sodium hydroxide and calcium oxide as additives, the vanillin yield after oxidation of the pretreated material could be increased by over 100 %. The generation of vanillin in NaLS in the solid state during ball milling was also observed for the first time confirming that mechanochemical transformation of the NaLS was taking place. Despite the difficulties associated with the analysis of such a heterogeneous and complex biopolymer, SEM imaging, GPC analysis and 2-D NMR analysis were used to identify some of the major chemical and physical changes occurring in the material during mechanochemical pretreatment. An HPLC analytical method for accurate measurement of the main oxidation products was also developed. The effect of using milling media of a different material on the pretreatment and subsequent oxidation reactions revealed that this pretreatment is transferable between different types and scale of equipment but that the results are sensitive to both materials of construction and storage conditions for analytical samples. The extrapolation of this pretreatment technique to other reactions of NaLS, hydrogenolysis for example, and to other biomass substrates was also investigated but with varying degrees of success, indicating that the mechanochemical changes can be subtle and highly reaction specific. Initial attempts at providing more mechanistic information were made through the synthesis and transformations of some simple lignosulphonate model compounds. These provided confirmation that the mechanistic scenario is complex and that several pathways are likely to be operating in parallel in the transformations of both model and polymer substrates.

Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau Mestre em Biotecnologia
The pre-treatment of biomass by ionic liquid (IL) is a method opening new possibilities of biomass fractionation for further valorisation of low value feedstock. This work is dedicated to study on the pre-treatment and fractionation of different types of lignocellulosic biomass into its major constituent fractions (cellulose, hemicellulose and lignin), using ILs. The biomass tested was: wheat straw, sugarcane bagasse, rice straw and triticale. Initially, the optimised methods were development basing on two methodologies described in the literature. This method allows the separation into high purity carbohydrate-rich (cellulose and hemicellulose) and lignin-rich fractions and permits an efficient IL recovery. The possibility of IL reuse was confirmed, demonstrating the great potential of the established method. The pre-treatment of various biomasses confirms the versatility and efficiency of the optimised methodology since not only the complete macroscopic dissolution of each biomass was achieved but also the fractionation process was successfully performed. Pre-treatment of sugarcane bagasse and triticale allowed to obtained cellulose samples rich in carbohydrate up to 90 wt %. In order to verify the potential further applicability of the obtained carbohydrate-rich fractions, as well as to evaluate the pre-treatment efficiency, the cellulose-rich fraction resulting from 1-ethyl-3-methylimidazolium acetate ([emim][OAc]) pre-treatment was subjected to enzymatic hydrolysis. Results showed a very high digestibility of the cellulose-rich samples and confirmed a high glucose yield for the optimised pre-treatment methodology. The samples obtained after the pre-treatment with ILs were qualitatively and quantitatively analysed by Fourier Transform Infrared Spectroscopy (FTIR). After the pre-treatment, the purity of the recovered ILs was evaluated through Nuclear Magnetic Resonance spectroscopy (NMR). The enzymatic hydrolysis results were analysed by High-Performance Liquid Chromatography(HPLC).

Microalgae have recently attracted considerable attention as a potential substrate for biofuel production. Through the anaerobic digestion process, microalgal biomass can be converted to biogas. Although the first work on anaerobic digestion of microalgae appeared in the 1950s, for a long time further information on AD of microalgae was scarce. This study assessed the potential for energy recovery from microalgal biomass grown in two large-scale systems in Spain: a closed tubular photobioreactor (PBR) and an open raceway. A series of digestion trials was carried out using freeze dried microalgae (FDA) from the PBR and fresh frozen microalgae (FFA) from the open raceway system as feedstock. Results from biochemical methane potential (BMP) assays showed that both feedstocks were poorly degraded and gave low methane yields. The specific methane yields of FDA and FFA were 0.161 and 0.220 L CH4 g-1 VS , respectively, which is only about 30% and 44% of the Theoretical Methane Potential (TMP) of these substrates based on their elemental composition. Digestion of FDA under semi-continuous conditions was stable at feedstock concentrations of up to 10% VS, equivalent to a hydraulic retention time of 20 days. Specific methane yields (SMY) were 0.11 - 0.12 L CH4 g-1 VS, corresponding to 69 - 75% of the value obtained from BMP. Digestion of FDA at 20% VS concentration gave only 0.09 L CH4 g-1 VS which is 56% of the value from BMP, or ~21% of the measured calorific value (CV). The digesters operating at 20% VS were able to achieve meta-stable operation at very high total ammonia nitrogen (TAN) concentrations of up to 12 g L-1 while showing reasonable methane production. They therefore showed a degree of adaptation to high TAN, but no evidence of improved biomass degradation even after operating periods in excess of 800 days. Results from the isotope labelling experiment indicated that syntrophic methanogenic pathway was the major route in high TAN concentration digesters. Digestion of FFA was stable at feedstock concentration of 4.33% VS and OLR up to 3.5 g VS L-1 day-1. SMY obtained under semi-continuous conditions was ~0.13 L CH4 g-1 VS, corresponding to 23% of the measured CV. A series of pretreatments were carried out on FFA, and the combined thermal-alkaline pretreatment (dosage of 3% w/w NaOH and incubated in water bath at 80 oC for 2 hours) enhanced SMY by 42% compared with that of untreated FFA obtained under batch condition. The results from semi-continuous condition indicated that some improvement was achieved with the thermal alkaline pretreatment, but there were also signs of inhibition due to the high alkaline dosages of 3% NaOH (w/w) required. There is clearly scope for optimisation of the treatment of feedstock and adaptation of the inoculum.

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.

Fast pyrolysis of biomass is a significant technology for producing pyrolysis liquids [also known as bio-oil], which contain a number of chemicals. The pyrolysis liquid can be used as a fuel, can be produced solely as a source of chemicals or can have some of the chemicals extracted and the residue used as a fuel. There were two primary objectives of this work. The first was to determine the fast pyrolysis conditions required to maximise the pyrolysis liquid yield from a number of biomass feedstocks. The second objective was to selectively increase the yield of certain chemicals in the pyrolysis liquid by pre-treatment of the feedstock prior to pyrolysis. For a particular biomass feedstock the pyrolysis liquid yield is affected by the reactor process parameters. It has been found that, providing the other process parameters are restricted to the values shown below, reactor temperature is the controlling parameter. The maximum pyrolysis liquid yield and the temperature at which it occurs has been found by a series of pyrolysis experiments over the temperature range 400-600°C. high heating rates > 1000°C/s; pyrolysis vapour residence times <2 seconds; pyrolysis vapour temperatures >400 but <500°C; rapid quenching of the product vapours. Pre-treatment techniques have been devised to modify the chemical composition and/or structure of the biomass in such a way as to influence the chemical composition of the pyrolysis liquid product. The pre-treatments were divided into two groups, those that remove material from the biomass and those which add material to the biomass. Component removal techniques have selectively increased the yield of levoglucosan from 2.45 to 18.58 mf wt.% [dry feedstock basis]. Additive techniques have selectively increased the yield of hydroxyacetaldehyde from 7.26 to 11.63 mf w.% [dry feedstock basis]. Techno-economic assessment has been carried out on an integrated levoglucosan production process [incorporating pre-treatment, pyrolysis and chemical extraction stages] to assess which method of chemical production is the more cost effective. It has been found that it is better to pre-treat the biomass in order to increase the yield of specific chemicals in the pyrolysis liquid and hence improve subsequent chemicals extraction.

The overall objective of this work was to compare the effect of pre-treatment and catalysts on the quality of liquid products from fast pyrolysis of biomass. This study investigated the upgrading of bio-oil in terms of its quality as a bio-fuel and/or source of chemicals. Bio-oil used directly as a biofuel for heat or power needs to be improved particularly in terms of temperature sensitivity, oxygen content, chemical instability, solid content, and heating values. Chemicals produced from bio-oil need to be able to meet product specifications for market acceptability. There were two main objectives in this research. The first was to examine the influence of pre-treatment of biomass on the fast pyrolysis process and liquid quality. The relationship between the method of pre-treatment of biomass feedstock to fast pyrolysis oil quality was studied. The thermal decomposition behaviour of untreated and pretreated feedstocks was studied by using a TGA (thermogravimetric analysis) and a Py-GC/MS (pyroprobe-gas chromatography/mass spectrometry). Laboratory scale reactors (100g/h, 300g/h, 1kg/h) were used to process untreated and pretreated feedstocks by fast pyrolysis. The second objective was to study the influence of numerous catalysts on fast pyrolysis liquids from wheat straw. The first step applied analytical pyrolysis (Py-GC/MS) to determine which catalysts had an effect on fast pyrolysis liquid, in order to select catalysts for further laboratory fast pyrolysis. The effect of activation, temperature, and biomass pre-treatment on catalysts were also investigated. Laboratory experiments were also conducted using the existing 300g/h fluidised bed reactor system with a secondary catalytic fixed bed reactor. The screening of catalysts showed that CoMo was a highly active catalyst, which particularly reduced the higher molecular weight products of fast pyrolysis. From these screening tests, CoMo catalyst was selected for larger scale laboratory experiments. With reference to the effect of pre-treatment work on fast pyrolysis process, a significant effect occurred on the thermal decomposition of biomass, as well as the pyrolysis products composition, and the proportion of key components in bio-oil. Torrefaction proved to have a mild influence on pyrolysis products, when compared to aquathermolysis and steam pre-treatment.

With the State of Alagoas as the third largest citrus producer in the Northeast region of Brazil, specifically cultivating Laranja Lima, being of fundamental importance the study of the hydrolyzate of Laranja Lima albedo for the planning of bioethanol production. The characterization of the Lima Orange albedo from the Cooplal juice industry of the municipality of Santana do Mundaú was carried out at the Bioflex 01 Industrial Laboratory of GRANBIO. For the hydrolysis process of the biomass were used the acids: hydrochloric, nitric, phosphoric and sulfuric with concentrations of 0.5 and 1.0% and periods of 30, 60, 90 and 120 minutes. The experimental design was completely randomized in the 4 x 2 x 4 factorial scheme, with three replications. Comparisons of the acid type averages within the concentrations and within the evaluation periods were done through the Tukey test at 5% probability. The hydrolysis with sulfuric acid obtained the best results for all variables studied. It is concluded that the hydrolysis process makes fermentable sugars of cellulose and hemicellulose available for the fermentation process.
Tendo o Estado de Alagoas como o terceiro maior produtor de citrus da região Nordeste do Brasil, cultivando especificamente Laranja Lima, sendo de fundamental importância o estudo do hidrolisado do albedo de Laranja Lima para o planejamento da produção de bioetanol. A caracterização do albedo da Laranja Lima da indústria de suco da Cooplal do município de Santana do Mundaú, foi realizado no Laboratório Industrial Bioflex 01 da GRANBIO. Para o processo de hidrólise da biomassa foram utilizados os ácidos: clorídrico, nítrico, fosfórico e sulfúrico com concentrações de 0,5 e 1,0% e períodos de 30, 60, 90 e 120 minutos. O delineamento experimental utilizado foi o inteiramente casualizado no esquema fatorial de 4 x 2 x 4, com três repetições. As comparações das médias de tipos de ácidos dentro das concentrações e dentro dos períodos de avaliação foram feitas através pelo teste de Tukey a 5% de probabilidade. A hidrólise com o ácido sulfúrico obteve os melhores resultados para todas variáveis estudados. Conclui-se que o processo de hidrólise torna os açúcares fermentescíveis da celulose e hemicelulose disponíveis para o processo fermentativo.

The severe effects associated with global warming and the rapid increase in oil prices are the driving forces behind the demand for clean carbon–neutral and biofuels such as bioethanol. Research studies are now focusing on using lignocellulosic biomass for bioethanol production due to concerns about food security and inflation. The chosen feedstock for this study was maize stover, given that it is the most abundant agricultural residue in South Africa. Maize stover consists of structural carbohydrates that can be enzymatically converted into fermentable sugars. The major drawback in the production of bioethanol from lignocellulosic biomass has been its high equipment and operational costs due to the use of acids and high enzyme loadings. The aim of this study was to investigate the possibility of optimizing the enzyme hydrolysis of pre–treated maize stover without further increasing the amount of enzymes. The maximum glucose yield attained was 690 ± 35 mg of glucose per gram of substrate which is equivalent to a conversion efficiency of 119%. The preferred pre–treatment method used was 3% sulphuric acid for 60 minutes at 121oC and the enzymatic hydrolysis process was performed at a 5% substrate loading, 50oC and pH 5.0 using 30 FPU per gram of cellulose in the presence of 1.25 g.L–1 of Tween 80 for 48 hours. The addition of Tween 80 increased the glucose yields by 23 % and thus, it has the potential of lowering the overall process costs by increasing the glucose yield without further addition of enzymes. Keywords: Bioethanol, maize stover, lignocellulosic biomass, pre–treatment, enzymatic hydrolysis
Thesis (M.Sc. Engineering Sciences (Chemical Engineering))--North-West University, Potchefstroom Campus, 2011.

Australia is one of the major producers and exporter of agricultural products. Annually, Australian agriculture produces approximately 151 Tg CO2 equivalent emissions. The use of fossil fuels in crop cultivation, harvesting and transportation are considered as the primary source of these greenhouse gas (GHG) emissions. Moreover, agronomic management and crop residues left in the field also contribute to these GHG emissions. Alternative waste management practices include the use of crop residues and agro-wastes as feedstocks for bioenergy production. Anaerobic digestion is considered as sustainable environmental technology to convert industrial sugarcane residues to carbon dioxide (CO2) - neutral biogas. The biogas thus produced can be used to produce heat, electricity and upgrade to biomethane for vehicle use. The produced biomethane can replace the diesel consumption associated with GHG emission in cane transport. Sugarcane is one among the most cultivated crop in the world. Australia alone produced nearly 33.5 million tonnes of cane in 2018 (FAO 2018). These large production of sugarcane lead to an increase in crop residues and agro-wastes from the sugarcane industry. In this study, an investigation regarding the anaerobic co-digestion of crop residues and agro-wastes from sugarcane industry viz, sugarcane trash (SCT) or sugarcane bagasse (SCB) with chicken manure (CM) was investigated in a batch experiment at 37 °C. In spite of various researches conducted till date about co-digestion of lignocellulosic waste with manure, no research data was available regarding the effect of feed ratio on co-digestion of SCT/SCB with CM. This research gap was investigated in this study. In addition to this, steam explosion pre-treatment of SCT/SCB was included to investigate how the pre-treatment influence methane yield among different feed ratios of SCT/SCB with CM. At first, SCT and SCB were subjected to steam explosion pre-treatment (steam impregnation at 130 °C for 5 minutes followed by steam explosion). Later, two sets of biochemical methane potential (BMP) tests were conducted at an Inoculum to Substrate Ratio (ISR) of 2. Co-digestion of untreated and steam exploded SCT or SCB with CM was investigated at feed ratios of 75:25, 50:50 and 25:75 on volatile solids (VS) basis. Assays with 100% untreated and steam exploded SCT or SCB were also included. Chemical analysis revealed that the steam explosion improved the VS content in pre-treated biomass compared with untreated biomass. The increase in VS was 1.6% and 5.7% in SCT and SCB, respectively. On the other hand, a slight reduction in total solids (TS) of nearly 4% and 1% were observed in the case of SCT and SCB, respectively. BMP results showed that the steam explosion had a profound effect on the methane production rates and yields, especially for SCB than SCT. Methane (CH4) yields of 201.8 and 199 ml CH4/gVSadded were obtained during the mono-digestion of untreated SCT and SCB, respectively. The corresponding values for 100% steam-exploded SCT and SCB were 207.5 and 225.6 ml/gVSadded, respectively. In comparison to mono-digestion, the co-digestion of SCB or SCT with CM did not improve the methane yields. Nevertheless, pre-treatment improved the methane production rates and yields of pre-treated biomass than untreated biomass. Among the studied feed ratios, best methane yields of 206.5 ml/gVSadded were obtained when steam-exploded SCT was co-digested with CM at 75:25 ratio. However, methane yields decreased with an increase in the amount of CM added. SCB also showed a similar trend. The best methane yield of 199.5 ml/gVSadded was obtained when steam-exploded SCB was co-digested with CM at 75:25 ratio. Among the tested feed ratios, all co-digestion mixtures except for 75:25 and 50:50 ratios of untreated SCT to CM showed synergistic effects. The best synergistic effect of 18.57% was observed when untreated SCB was co-digested with CM at 25:75 ratio. Kinetic modelling results confirmed that the steam explosion pre-treatment improved the methane production rates and yields by increasing the hydrolysis rate constant values. However, a higher hydrolysis rate constant was noticed for SCT than SCB. The highest hydrolysis rate constant of 0.16 d-1 was achieved at feed ratios of 50:50 and 25:75 of pre-treated SCT:CM. Interestingly, more than 75% of methane in pre-treated assays was produced by Day 11. The study thus suggests that the steam explosion can improve the methane production rates, yields and productivity of SCT and SCB. However, the use of CM as co-substrate did not improve the methane yields when compared to the mono-digestion of SCT or SCB, but a positive synergism was evident in most of the co-digestion feed ratios.
Thesis (Masters)
Master of Philosophy (MPhil)
School of Eng & Built Env
Science, Environment, Engineering and Technology
Full Text

Made available in DSpace on 2016-06-02T19:56:43Z (GMT). No. of bitstreams: 1 3641.pdf: 2915031 bytes, checksum: 75a88eb9fcd13120c484443ffeae1a1a (MD5) Previous issue date: 2011-02-28
Universidade Federal de Sao Carlos
The aim of this work was evaluated the sugarcane bagasse (SCB) pretreatment by aqueous ammonia, an alkaline method. Samples of SCB (in natura and steam exploded unwashed) were pretreated with ammonium hydroxide solution (NH4OH) at 1:5 solid-liquid ratio (by weight), in a bench scale. Preliminary assays were carried out employing NH4OH solution (28% w/w) at room temperature 24 ± 3 ⁰C by 7, 15 and 30 days. In these experiments, it was observed that the pretreatment was selective in removing lignin and hemicellulose. New experiments were carried out using at 50⁰C and NH4OH 15% during 30, 60 and 90 minutes. In these pretreatments the same behavior was observed. In the next assays, it decided to fix the reaction time in 60 minutes and the temperature in 100⁰C. Samples of in nature and steam exploded SCB were pretreated at diffent NH4OH concentrations (4 to 15%). Enzymatic hydrolysis assays were carried out in Erlenmeyers flasks (50⁰C, pH 4.8 and 250 rpm) using 30 FPU/g bagasse (Accellerase 1500, Genencor) and 5 CBU/g bagasse (BG, Genencor). Experiments were carried out employing in natura SCB (pretreated conditions 4, 10 and 15% NH4OH solution, 60 min., 100⁰C) with 3% of solid loading. A glucose conversion of 64.2% was reached in the best condition (10% NH4OH solution). Experiments were carried out employing steam exploded SCB (5, 10 e 15% NH4OH solution, 60 min. and 100⁰C) with 5% of solid loading. A glucose conversion of 79.9% was reached in the best condition (15% NH4OH solution). Hydrolysis experiments using higher solid loading (5% for in natura and 10% for steam exploded) and 30 FPU/g cellulose (Accellerase 1500) were carried out. A glucose conversion of 69.6% for in natura and 82.2% for steam exploded SCB were obtained. Fermentation assays (250 rpm, 30⁰C) employing commercial and industrial Saccharomyces cerevisiae were conducted, in a rich and poor medium. A theoretical fermentation yield up to 78% was found for the poor medium and around 88% for the rich medium. The industrial S. cerevisiae shows a value of yield slightly superior to those of commercial strain. Samples of SCB (before and after pretreatment) were analyzed by scanning electron micrograph (SEM).
O objetivo deste trabalho foi avaliar a etapa de pré-tratamento do bagaço de cana de açúcar empregando amônia aquosa, um método alcalino. Amostras de bagaço (in natura e explodido a vapor não lavado) foram tratadas na proporção 1:5 (massa de bagaço seco por massa de solução de NH4OH), em escala de bancada. Ensaios preliminares foram realizados empregando solução 28% (m/m) de NH4OH, a temperatura ambiente 24 ± 3 ⁰C por 7, 15 e 30 dias em recipiente fechado. Nestes experimentos verificou-se que o pré-tratamento foi seletivo na remoção de lignina e hemicelulose. Novos experimentos foram realizados fixando-se a temperatura em 50⁰C e a concentração de NH4OH em 15%. Avaliaram-se tempos de reação de 30, 60 e 90 min. Nestes prétratamentos o mesmo comportamento foi observado. Nos próximos ensaios o tempo de reação foi fixado em 60 min e a temperatura em 100⁰C. Amostras de bagaço foram pré-tratadas em soluções de NH4OH (4 a 15%). Experimentos de hidrólise enzimática foram realizados em frascos de Erlenmeyer (50⁰C, pH 4,8 e 250 rpm) empregando 30 FPU/g bagaço (Accellerase 1500, Genencor) e 5 CBU/g bagaço (BG, Genencor). Na hidrólise das amostras de bagaço in natura (pré-tratadas com soluções de NH4OH 4, 10 e 15%, 60 min, 100⁰C) com carga de sólidos de 3% a melhor conversão em glicose foi de 64,2% (amostra tratada NH4OH 10%). Na hidrólise da amostra de bagaço explodido (pré-tratadas com NH4OH 5, 10 e 15%, 60 min e 100⁰C) com carga de sólidos de 7% a melhor conversão em glicose foi de 79,9% (amostra tratada com NH4OH 15 %). Hidrólises com maior carga de sólidos, 5% (bagaço in natura) e 10% (bagaço explodido), utilizando 30 FPU/g celulose (Accellerase 1500, Genencor) foram realizadas. Nestes ensaios obteve-se conversão em glicose de 69,6% (bagaço in natura) e 82,2% (bagaço explodido). Experimentos de fermentação alcoólica (250 rpm, 30⁰C) foram realizados empregando levedura Saccharomyces cerevisiae (comercial e industrial) em meios de cultivo denominados rico e pobre . A eficiência na conversão da glicose em etanol nos experimentos foi acima de 78% (meio pobre ) e da ordem de 88% (meio rico ). A levedura industrial apresentou eficiência um pouco superior à comercial. As amostras de bagaço (antes e após o pré-tratamento) foram analisadas por microscopia eletrônica de varredura (MEV).

The fossil energy resources decrease and climate changes, caused by carbon dioxide (CO2) emissions, have led most industrialized countries to undertake policies aimed at the development and use of renewable energy sources. Among the renewable energies, vegetal biomasses play a key role because widely available and potentially able to cover up to 200% of the global energy demand. Vegetal biomasses can be used mainly as raw materials for the production of chemicals, biofuels and energy, in the increasingly important green economy concept based on biorefineries creation. Although the vegetal biomasses result widely available, rising costs of food raw material such as wheat, corn and sugar beet have raised a serious ethical problem using these resources. To avoid the use of such raw materials, the exploitation of lignocellulosic biomasses plays a fundamental role in the industry. However, for an efficient utilization of lignocellulosic biomasses, new technologies are required in order to transform the starting biomass into simple molecules, such as pentoses and hexoses sugars, more easily to use by the microrganism, which will have the task of producing both fine chemicals and bulk chemicals in an economically and environmentally sustainable processes. In this regard, industrial biotechnologies should be able to develop new microrganisms capable to face the harsh environmental conditions that occur during an industrial production process. For many of these productions the yeast Saccharomyces cerevisiae is largely used, not only because of its naturally ability to produce large ethanol amount, but also is widely known both at genetic and metabolic level, outlining a good starting point for the development of producers strains with high tolerance against different stresses occur during an industrial process. This is the view adopted by NEMO project (Novel high performance Enzymes and Microrganisms for conversion of lignocellulosic biomass to ethanol), belonging to the European Union seventh framework program, where it become of primary importance the development of microrganisms, especially S.cerevisiae, for the second generation ethanol production. Microrganisms must be, on the one hand able to efficiently utilize all the sugars released from lignocellulosic biomass pre-treatment, on the other hand should be more tolerant against process conditons, such as inhibitory compounds and environmental stresses. A point of relevant importance is the ability to utilize pentose sugars, like D-xylose, released in large amount after lignocellulose pre-treatment. Currently, worldwide researches are focused on the development of yeast strains engineered with xylose degradation pathways involving the pentose phosphate pathway. In fact the fungal pathway exploits xylose reductase and the xylitol dehydrogenase while the bacterial pathway exploits xylose isomerase; both pathways degrade D-xylose into D-xylulose, which will enter into pentose phosphate pathway. In addition to these two pathways studied since the ‘80s of the last century, there also two other poorly known metabolisms, described for the first time in the ‘70s, which produce alpha-ketoglutarate or pyruvate and glycolaldehyde through an oxidative xylose degradation. These pathways are composed of 5 enzymatic reactions by the Weimberg’s pathway and of 4 enzymatic reactions by the Dahms’ pathway, however they share the first 3 enzymatic reactions. After bioinformatics we were identified the presence of Weimberg’s pathway into Burkholderia xenovorans, while the reaction that characterizes the Dahms’ pathway has been identified in Escherichia coli. The encoding genes for these enzymatic activities were expressed in S.cerevisiae, and the capacity to grow on D-xylose as carbon source are evaluated. The reconstruction of these two pathways showed a poorly growth capacity on xylose. Such growth limitation seems to be related to several factors: the presence of bottlenecks associated to enzymes functionality, like D-xylonate dehydratase activity; the yeast ability to internalize xylose efficiently; the involved genes optimization. Another important aspect is the yeast ability to face and overcome environmental stresses encountered during an industrial process. The cytoplasmic membrane plays a key role in cellular homeostasis, being at the interface between the cell and the external environment, and reacting at environmental changes. The plant membrane protein TIL gives particular strength to the yeast cells when these are subjected to environmental stresses of industrial relevance, such as the presence of oxidative agents or during temperature changes. However, when TIL is expressed in an industrial and/or in an engineered laboratory strains, for industrial use, the protective effect against prolonged stress exposure and process conditions disappear. Finally, a further important aspect during an industrial process is the S.cerevisiae ability to tolerate the growth inhibitory compounds presence into pre-treated lignocellulose. In fact has been largely described how chemical compounds like aldehydes, organic acids and phenolic compounds, released during lignocellulose pre-treatment process, are toxic at certain concentration, inhibiting S.cerevisiae growth or causing yeast death. The growth performance of different wild type or engineered yeast strains are evaluated on spruce and giant cane lignocellulose pre-treated: in addition the same strains were tested on minimal formulated medium according to the spruce pre-treated composition. The results showed that the combination of low pH and the presence of organic acids, especially acetic acid and formic acid, are dramatically harmful for growth of both industrial strain, naturally more tolerant, and engineered strain, for the production and recycle of L-ascorbic acid. However, the behavior of engineered strain for production and recycle of L-ascorbic acid is interesting at low pH, because showed higher tolerance than other strains in terms of growth rate and ethanol production and productivity. Despite the positive results obtained by engineering microrganisms, especially S.cerevisiae, in laboratory, their industrial uses still remain limited. Therefore, appears extremely important the construction of more robustness strains, able to withstand different environmental conditions along an entire industrial process, with consequent influence on yields, production and productivity. For these reasons, the research is aimed to combine these aspects to provide the best microrganism possible to industry productions.

Este trabalho investigou o efeito da temperatura nos sistemas aneróbios com células imobilizadas tendo como estudo de caso um sistema anaeróbio em duas fases. Inicialmente, foram realizados experimentos preliminares com um sistema em duas fases composto por Reator Acidogênico Horizontal Tubular (RAHT) seguido de Reator Anaeróbio Horizontal de Leito Fixo (RAHLF), nas temperaturas de 15ºC, 20ºC e 25ºC. Os resultados mostraram que o RAHT alcançou 48% de remoção de DQO e que a desvantagem da ausência de microrganismos consumidores de H2 no sistema praticamente não afetou a produção de ácido acético. Pôde-se observar que na faixa de temperatura estudada o RAHT não apresentou mudanças significativas em seu desempenho. Posteriormente foram realizados experimentos com cinco reatores metanogênicos do tipo RAHLF, alimentados com esgoto sintético simulando o efluente do RAHT, com velocidades de 10,4 cm/h, a 52,0 cm/h e temperatura de 15ºC a 35ºC. Os resultados permitiriam o desenvolvimento de um modelo empírico-estatístico para simulação do desempenho dos reatores, tendo como variáveis a velocidade superficial do líquido sobre as biopartículas e a temperatura de operação. Os resultados preditos pelo modelo demonstraram boa representatividade dos valores experimentais. Com isso, foi possível observar as influências da velocidade superficial (vs) e da temperatura, nas concentrações residuais de substrato (Sr) e nas constantes cinéticas aparentes de primeira ordem (K1app). Conclui-se então, que apesar do aumento de vs resultar em maiores valores de K1app, também foi observado aumento no valor de Sr indicando que existe um tempo de contato mínimo entre os microrganismos e o substrato.
The effects of temperature and superficial velocity in an anaerobic methanogenic immobilized cell rector of a two phase-system were investigated. Preliminarily, a Tubular Horizontal Acidogenic Reactor (THAR) followed by Horizontal-flow Anaerobic Immobilized Biomass (HAIB) composed the experimental system, operated at the temperatures of 15°C, 20°C and 25°C. COD removal efficiency of 48% was observed in the THAR. Likewise, the disadvantage of the absence of H2-consumer methanogenics microorganisms in the system almost did not affect the production of acetic acid. The temperature variation has not caused significant changes in the THAR performance. The next step was the development of experiments using five methanogenics HAIB reactors fed on synthetic wastewater simulating THAR effluent having superficial velocities from 10,4 cm/h to 52,0 cm/h and temperature from 15°C to 35°C. The results enabled the development of a statistical-empiric modeling to simulate the reactors performance using the liquid superficial velocities and the temperature operation as model variables. The model demonstrated a good agreement with the experimental values. The influence of the superficial velocities (vs) and temperature, in the substrate residual concentration (Sr) and in the first order (K1app) apparent kinetic constant was observed. Despite the K1app values have increased largely with vs, the Sr concentration also increased. These results permit to conclude that a minimum contact time between the microorganisms and the substrate may be necessary in such processes.

Orientador: Celso Eduardo Tuna
Resumo: A agroindústria nacional brasileira dispõe de uma grande variedade de unidades agrícolas que geram elevada quantidade de resíduos como o bagaço de cana-de-açúcar. Mesmo diante da crescente utilização desse material, o excedente ainda é da ordem de milhões de toneladas, causando problemas de estocagem e poluição ambiental. Devido a sua estrutura complexa e sua recalcitrância, a etapa de pré-tratamento representa o desafio mais crítico para a viabilização da utilização do bagaço de cana-de-açúcar dentro do contexto de uma biorrefinaria. O pré-tratamento busca facilitar o acesso aos componentes estruturais da biomassa, permitindo sua utilização na cadeia produtiva. Existem diferentes métodos de pré-tratamento como os físicos, químicos e biológicos ou uma combinação de todos esses, de modo que a geração de resíduos ambientalmente perigosos e/ou altos insumos energéticos é o gargalo. Neste sentido, rotas tecnológicas alternativas vem sendo estudadas e a cavitação hidrodinâmica desponta-se como uma promissora rota para o pré-tratamento de biomassa liberando grandes magnitudes de energia e induzindo a transformações físicas e químicas, favorecendo o rompimento da matriz carboidrato-lignina. Neste contexto, este trabalho empregou a cavitação hidrodinâmica para potencializar o pré-tratamento alcalino do bagaço de cana-de-açúcar. Para isto, projetou-se um reator de cavitação hidrodinâmica com tubo de Venturi utilizando como base uma abordagem computacional para a dinâmica dos fluidos. ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The Brazilian national agroindustry has a large variety of agricultural units that generate high amounts of waste such as sugarcane bagasse. Even with the increasing use of this material, the surplus is still in the order of millions of tons, causing problems of stocking and environmental pollution. Due to its complex structure and recalcitrance, the pretreatment stage represents the most critical challenge for the feasibility of using sugarcane bagasse within the context of biorefinery. Pretreatment seeks to facilitate access to the structural components of biomass, allowing its use in the production chain. There are different pretreatment methods such as physical, chemical, physicochemical and biological or a combination of all of these, so that the generation of environmentally hazardous waste and / or high energy inputs is the bottleneck. In this sense, alternative technological routes have been studied and hydrodynamic cavitation emerges as a promising route for biomass pretreatment releasing large energy magnitudes and inducing physical and chemical transformations, favoring the rupture of the carbohydrate-lignin matrix. In this context, this thesis employed hydrodynamic cavitation as a physical means to improve the alkaline pre-treatment of sugarcane bagasse. The hydrodynamic cavitation reactor with Venturi tube was modeled by a computational approach to fluid dynamics, in order to evaluate the influence of the pressure ratio, the length and diameter of the throat and ... (Complete abstract click electronic access below)
Doutor

碩士
國立臺北科技大學
環境工程與管理研究所
106
The urban waste disposal problem is an important issue in Taiwan. This study selected large-scale waste incineration plants and refuse transfer stations in the municipalities (NT City and KH City) and outlying islands in the domestic municipalities and in the outlying seasons of the outlying counties (PH counties). For the sampling sites, and comparison of the two municipalities in North-South comparison with PH County Tourism MSW season. After the actual field sampling, the garbage samples of NT City were used as the basis for the raw material for the development of biomass fuel, and the method of designing the solar energy to crush MSW materials was evaluated as a reference for the development of biomass fuel energy. From the sampling results and crushing experiments, it is known that the proportion of MSW contained Mandatory Recyclables in NT City (13.54%) is greater than that in KH City (11.78%); the Mandatory Recyclables in MSW in peak season (17.16%) is greater than in the off-season (11.88). %). This result shows that due to the excessive amount of plastic recyclables in the northern area, the total amount of recyclables should be greater than that in the southern area, while the waste in the outlying areas caused by sightseeing can be clearly seen. In the crushing experiments, papers with high calorific value and low chlorine content, and deciduous and fiber cloths of bamboo, bamboo and straw were used for subdivision and crushing, and the crushing efficiency was high to low for paper (91.82%), bamboo, straw, and deciduous (75.12%) and fiber cloths (16.11%). Another item of the MSW crushing test is to reduce the physical composition of the sample to a known sampling box and increase the volume by 30.27% after crushing. Furthermore, this study calculates the power consumption required for the crushing test, converts and calculates the required solar energy equipment area to approximately 23 to 35 international standard-size basketball courts, and calculates the annual cost of crushing by the cost estimate to the monetary value of 2018. Counted at NT$285/metric ton. Therefore, the announcement that the recyclables should be strictly recycled will achieve real garbage reduction. The solar biofuel pretreatment crushing equipment proposed by this study can also serve as a reference for future projects.

The present work is devoted to study the pre-treatment of lignocellulosic biomass, especially wheat straw, by the application of the acidic ionic liquid (IL) such as 1-butyl-3-methylimidazolium hydrogen sulphate. The ability of this IL to hydrolysis and conversion of biomass was scrutinised. The pre-treatment with hydrogen sulphate-based IL allowed to obtain a liquor rich in hemicellulosic sugars, furans and organic acids, and a solid fraction mainly constituted by cellulose and lignin. Quantitative and qualitative analyses of the produced liquors were made by capillary electrophoresis and high-performance liquid chromatography. Pre-treatment conditions were set to produce xylose or furfural. Specific range of temperatures from 70 to 175 °C and residence times from 20.0 to 163.3 min were studied by fixing parameters such as biomass/IL ratio (10 % (w/w)) and water content (1.25 % (w/w)) in the pre-treatment process. Statistical modelling was applied to maximise the xylose and furfural concentrations. For the purpose of reaction condition comparison the severity factor for studied ionic liquid was proposed and applied in this work. Optimum conditions for xylose production were identified to be at 125 °C and 82.1 min, at which 16.7 % (w/w) xylose yield was attained. Furfural was preferably formed at higher pre-treatment temperatures and longer reaction time (161 °C and 104.5 min) reaching 30.7 % (w/w) maximum yield. The influence of water content on the optimum xylose formation was also studied. Pre-treatments with 5 and 10 % (w/w) water content were performed and an increase of 100 % and 140 % of xylose yield was observed, respectively, while the conversion into furfural maintained unchanged.

The main purpose of this dissertation is to scrutinise the potential of two distinct high-pressure technologies - CO2/H2O mixture and ammonia – for lignocellulosic biomass processing following the biorefinery concept. High-pressure CO2/H2O mixture took benefits from the formation of in-situ carbonic acid and involved the integration of both pre-treatment and hydrolysis steps. Due to its acidic effect, this technology was able to selectively hydrolyse the hemicellulosic fraction of biomass producing C5-oligomeric sugar-rich aqueous stream. Later, the C5-sugars present in this stream were successfully converted into furfural with high yield and selectivity using the same catalytic effect of high-pressure mixture of CO2/H2O. Additionally, the leftover materials enriched in cellulose demonstrated to be highly susceptible for enzymatic hydrolysis leading the production of highly concentrated solution of upgradable glucose. High-pressure ammonia relied on the development of a new ammonia-based technology called “Compacted Biomass with Reduced Ammonia” to pre-treat pelletised biomass, at reduced ammonia loadings. This process combined the advantages of conversion of native crystalline cellulose Iβ into highly digestible cellulose III and the benefits of ammonolysis of cell wall ester cross-links. Besides, the proposed process allowed obtaining fermentable sugars, either C5 or C6-sugars, and ethanol yields comparable to industrially relevant technologies i.e. AFEXTM (Ammonia Fiber Expansion) and steam explosion. Additionally, the proposed approach demonstrated to be a feedstock-independent technology capable to handle different types of biomasses, regardless of their macromolecular composition and morphological structure, to produce high yields of fermentable sugars. Both explored technologies demonstrated to be highly effectives for lignocellulosic biomass valorisation, showcasing their potential as sustainable technologies applicable in the biorefinery approach.

Dissertação de Mestrado Integrado em Engenharia Química apresentada à Faculdade de Ciências e Tecnologia
Com o elevado crescimento populacional aumentou o consumo de combustíveis fósseis e com estes a produção de CO2. Na tentativa de reduzir estas emissões é imprescindível enveredar pelo uso de combustíveis alternativos, como o bioetanol. Este é o biocombustível mais utilizado no setor dos transportes e pode ser produzido a partir de resíduos de biomassa lenhocelulósica, tirando partido da sua abundância e do seu baixo custo. No presente trabalho utilizou-se uma matéria-prima abundante na zona do Baixo Mondego, a palha de arroz (PA), para a produção de bioetanol. A produção de bioetanol a partir de material lenhocelulósico é constituída por quatro etapas: o pré-tratamento, a hidrólise dos hidratos de carbono a açúcares simples, a fermentação dos açúcares em etanol e a sua purificação. Para este fim foi estudado o pré-tratamento alcalino, tendo sido realizados diversos ensaios em que se analisou a influência da concentração de NaOH, da temperatura, do tempo e ainda do pré-tratamento prévio com HCl. Nos ensaios de pré-tratamento cujas condições operatórias levaram à obtenção de melhores resultados de redução do teor de lenhina e de hidrólise enzimática (121ºC, 2 horas e 120 e 150 mg(NaOH)/g(PA)) foram sujeitos a um aumento de escala. Para isso, foi utilizada uma autoclave de maiores dimensões e o pré-tratamento foi realizado em frascos de 1 L em vez de 250 mL. Após caraterização do material sólido obtido, verificou-se que se obteve uma percentagem de deslenhificação de 87.8 e 90.4% nos ensaios realizado com 120 e com 150 mg(NaOH)/g(PA), respetivamente. Procedeu-se depois à hidrólise enzimática da biomassa com o complexo enzimático Cellic CTec2. Foram realizados ensaios de hidrólise enzimática em regime descontínuo e semi-descontínuo durante 72 horas, tendo-se concluído que estes não eram viáveis para a carga de hidratos de carbono estabelecida. Em alternativa foram realizados ensaios de SSF (Simultaneous Saccharification & Fermentation) em regime semi-descontínuo, onde se utilizou o mesmo complexo enzimático e a levedura S. cerevisiae ATCC 26602. Nestes obteve-se uma produção de etanol de 30.9 e 42.1 g/L, com uma produtividade de 0.64 e 0.38 g/(L h) e rendimento de conversão glucose-etanol de 69.3 e 95.3%, usando no pré-tratamento 120 e 150 mg(NaOH)/g(PA), respetivamente. Realizou-se ainda um ensaio de SSF com um meio nutricional alternativo sintético em que se obteve uma concentração máxima de etanol de 33.3 g/L, uma produtividade de 0.46 g/(L h) e um rendimento de 70.4%. Concluindo, foram alcançados os objetivos inicialmente propostos para o presente trabalho, tendo-se obtido uma produção de etanol satisfatória com os pré-tratamentos usados com a palha de arroz numa primeira fase de testes.
With the high population growth, the consumption of fossil fuels has increased and consequently the production of CO2. In an attempt to reduce these emissions, it is essential to look for alternative fuels, such as bioethanol. This is the most used biofuel in the transport sector and can be produced from lignocellulosic biomass waste, due to its abundance and its low cost. In the present work an abundant raw material from Baixo Mondego zone was used, rice straw (RS), for the production of bioethanol. The production of bioethanol from lignocellulosic material consists of four stages: pre-treatment, hydrolysis of carbohydrates to simple sugars, fermentation of sugars in ethanol and its purification. For this purpose, the alkaline pre-treatment was studied, and several tests were carried out in order to evaluate the influence of NaOH concentration, temperature, time and previous pre-treatment with HCl. Pretreatment trials leading to the highest lignin reduction and enzyme hydrolysis (121°C, 2 hours and 120 and 150 mg(NaOH)/g(RS)) were scaled up. In this case, a larger autoclave was used and pretreatment was carried out in 1 L flasks instead of 250 mL. After the characterization of the obtained solid material, it was found that a delignification percentage of 87.8 and 90.4% was obtained in the assays performed with 120 and 150 mg(NaOH)/g(RS), respectively. The enzymatic hydrolysis of the biomass was then performed with the Cellic CTec2 enzyme complex. Enzymatic hydrolysis assays were performed in a batch and semi-batch regime for 72 hours, and it was concluded that these were not viable for the established carbohydrate quantity. Alternatively, SSF assays were performed in a semi-discontinuous regime, where the same enzyme complex and the yeast S. cerevisiae ATCC 26602 were used. Using the pre-treated samples produced with 120 and 150 mg(NaOH)/g(RS), a concentration of 30.9 and 42.1 g/L of ethanol was obtained, with a productivity of 0.64 and 0.38 g/(L h) and a glucose-ethanol conversion efficiency of 69.3 and 95.3%, respectively. An SSF test was also performed with a synthetic alternative nutrient medium in which was a maximum ethanol concentration 33.3 g/L was obtained, as well as a productivity of 0.46 g/(Lh) and a conversion efficiency of 70.4%. In conclusion, the objectives initially proposed for the present work were reached and a satisfactory ethanol production was obtained with this preliminary approach used to pre-treat the rice straw.

Dissertação de Mestrado Integrado em Engenharia Química apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra
O desenvolvimento de novas tecnologias baseadas em recursos renováveis (em particular, a biomassa lenhocelulósica) têm o potencial de conduzir a transformações económicas, sociais e ambientais com impacto favorável na sociedade. O pré-tratamento da biomassa lenhocelulósica com líquidos de baixa temperatura eutéctica/baixa temperatura de transição vítrea (líquidos de BTE/BTTV) surgiu recentemente como um pré-tratamento para a remoção selectiva da lenhina, numa forma próxima da lenhina original, permitindo a sua valorização. Os líquidos de BTE/BTTV são mais baratos e, na generalidade, são renováveis e menos poluentes que os solventes mais utilizados na valorização da biomassa. O estudo efectuado neste trabalho começou com a dissolução de madeira de Eucalipto (Eucalyptus globulus) em diferentes líquidos de BTE/BTTV, nomeadamente, (i) os líquidos [GC 20:1], [GC 100:1] (líquidos compostos por glicerol e cloreto de colina, razão molar 20:1 e 100:1, respectivamente), (ii) os líquidos [GCP 20:1] e [GCP 100:1] (líquidos compostos por glicerol e carbonato de potássio, razão molar 20:1 e 100:1, respectivamente) e (iii) os líquidos [LCCETMA 5:1], [LCCETMA (1) 5:1] e [LCCETMA (2) 5:1] (líquidos compostos por ácido láctico (≥98, 80 e 95%, respectivamente) e cloreto de (2-cloroetil) trimetilamónío, razão molar 5:1). A madeira de eucalipto utilizada neste trabalho continha um teor total de lenhina de 25,3%. Os líquidos [GCP 20:1] e [GCP 100:1] foram os que apresentaram maiores rendimentos de dissolução (14,7 e 18,5% , respectivamente); contudo, não mostraram ser selectivos para a lenhina, tendo dissolvido apenas 0,8% e 1,4% de lenhina. Por outro lado, os líquidos [LCCETMA 5:1], [LCCETMA (1) 5:1] e [LCCETMA (2) 5:1], apesar de terem apresentado rendimentos de dissolução mais baixos (11,5, 8,9 e 9,5%, respectivamente), mostraram ser mais selectivos para a lenhina, dissolvendo 7,8, 4,3 e 5,6%, respectivamente). Por fim, os líquidos [GC 20:1] e [GC 100:1] apresentaram rendimentos de dissolução baixos (7,9 e 8,3%, respectivamente) e não foram selectivos para a lenhina. Dos líquidos estudados, conclui-se que o [LCCETMA (2) 5:1] é o mais selectivo para a lenhina e de baixo custo e o líquido [GCP 100:1] é o que permite obter maior rendimento de dissolução de madeira. Realizou-se posteriormente a dissolução de três espécies de madeira diferentes, Mimosa (Acacia dealbata), Giesta (Cytisus sp.) e Silva (Rubus sp.), nos líquidos seleccionados, [GCP 100:1] e [LCCETMA (2) 5:1]. Estas madeiras continham, respectivamente, 26,5 , 22,5 e 29,6% de lenhina. Ao contrário do que sucedeu com as outras espécies, a dissolução da madeira de Mimosa nestes líquidos mostrou ser muito selectiva para a lenhina. De facto, o líquido [GCP 100:1] permitiu dissolver 8,4% desta madeira, correspondendo 7,7% a lenhina dissolvida; por sua vez, a dissolução com o líquido [LCCETMA (2) 5:1] apresentou um rendimento de 9,9%, sendo 8,8% lenhina dissolvida. Por último foram efectuadas dissoluções da madeira de Mimosa com os mesmos líquidos [GCP] e [LCCETMA(2)] mas com diferentes razões molares com o objectivo de perceber a influência da razão molar na selectividade para a lenhina. Nos líquidos [GCP], o aumento da proporção de glicerol de (20:1) para (200:1), (líquidos [GCP 20:1] e [GCP 200:1]) permitiu aumentar em cerca de 11% o teor de lenhina dissolvida. Por sua vez, na dissolução da Mimosa com o líquido [LCCETMA (2)], ao aumentar a proporção de ácido láctico de (5:1) para (10:1) (líquido [LCCETMA (2) 5:1] e [LCCETMA (2) 10:1]), a quantidade de lenhina dissolvida aumentou 5,6%. Na tentativa de precipitar a lenhina dissolvida nos líquidos de BTE/BTTV obtiveram-se rendimentos de precipitação relativamente baixos. Por exemplo, ao utilizar a água como anti-solvente, o rendimento de precipitação máximo foi de 45%. É então necessário prosseguir estudos nesta área para melhorar este desempenho.
The development of new technologies using renewable resources (such as lignocellulosic biomass) might be helpful to induce important economic, social and environmental changes within the society. The pre-treatment of lignocellulosic biomass using deep eutectic solvents/low transition temperature mixtures (DES/LTTMs), has recently appeared in the market as a solution to primarily remove the lignin, as similarly as possible to the original, so that it might be re-used. Note, that the deep eutectic solvents/low transition temperature mixtures are economical, renewable and environmentally friendly solvents. The present study was initiated by the dissolution of Eucalyptus wood (Eucalyptus globulus) into several different DES/LTTMs, namely: (i) [GC 20: 1], [GC 100: 1] (liquids comprising choline chloride and glycerol, with a molar ratio of 20: 1 and 100: 1, respectively); (ii) the [GCP 20: 1] and [GCP 100: 1] (liquids including glycerol and potassium carbonate, with a molar ratio of 20: 1 and 100: 1, respectively) and (iii) [LCCETMA 5: 1], [LCCETMA(1) 5: 1] and [LCCETMA(2) 5: 1] (composed by lactic acid (≥98%, 80% and 95%, respectively) and (2 chloroethyl) trimethylammonium chloride with a molar ratio of 5: 1. Both the [GCP 20: 1] and [GCP 100: 1] liquids presented the higher dissolution efficiency (of 14,7% and 18,5%, respectively); nonetheless both proved not to be selective for lignin (having dissolved only 0,8% and 1,4% of the total amount of 25,3% of lignin). Subsequently, the results for the [LCCETMA 5: 1], [LCCETMA (1) 5: 1] and [LCCETMA (2) 5: 1] liquids, revealed a lower dissolution efficiency (11,5%, 8,9% and 9,5%, respectively), however they proved to more selective for lignin (having dissolved 7,8%, 4,3% and 5,6% of the total content, which was 25,3%). Finally, the results for the [GC 20: 1] and [GC 100: 1] liquids, presented low efficiency for the lignin dissolution (of about 7,9% and 8,3%, respectively) and proved also not to be selective for lignin. Therefore, the study concludes that the [LCCETMA (2) 5: 1] liquid is not only the more selective for lignin, but is also the less expensive one. On the other hand, the [GCP 100:1] liquid allows to obtaining higher yields of the wood dissolution. Afterwards, the dissolution procedure was applied on three different types of wood (Mimosa – Acacia dealbata; Broom – Cytisus sp; and Silva – Rubus sp), using the [GCP 100: 1] and [LCCETMA (2) 5: 1] liquids. The Mimosa wood dissolution using the [GCP 100: 1] and [LCCETMA (2) 5: 1] liquids proved to be highly selective for the lignin. The dissolution with the [GCP 100: 1] liquid displayed a 8,4% dissolution yield and dissolved 7,7% of the lignin (of a total amount of: 26,5%); as for the dissolution with the [LCCETMA(2) 5: 1] liquid, the dissolution yield was of 9,9% and it dissolved about 8,8% of the lignin (of a total of: 26,5%). In contrast, the dissolution of the Broom and Silva wood using the [GCP 100: 1] and [LCCETMA (2) 5: 1] liquids, proved not to be selective for lignin. Finally, the Mimosa wood was also dissolved with [GCP] liquid (which comprises glycerol and potassium carbonate) and [LCCETMA (2)] liquid (composed by lactic acid (95%) and (2-chloroethyl) trimethylammonium chloride, using different molar ratios, in order to understand the effect that these (the molar ratios) have on the lignin selection. By increasing the glycerol proportion in the [GCP] liquid – from (20: 1) to (200: 1), for the [GCP 20: 1] and [GCP 200: 1] liquids – the amount of dissolved lignin increased 5,6 %. During the precipitation phase, the results of the dissolved lignin using the DES / LTTMs presented relatively lower precipitation yields. For instance, when using water as an anti-solvent, the maximum precipitation yields were 44,9%. Thus, it is required to undertake further studies about the lignin precipitation.