In recent years, third-generation--or algae-based biofuels--have been studied extensively in order to reduce the risks of compromised food security, solve biofuel issues from past generations and supply continuous feedstock from energy crops. With the goal of a zero-carbon future, bioenergy with carbon capture and storage (BECCS) is a technology that extends to multiple areas--including algae-based biofuels that avoid greenhouse emissions from biomass processing. Algae are aquatic plants or microorganisms, classified as micro and macroalgae; they are of considerable scientific interest because they are fast-growing, with a photosynthetic metabolism that generates carbon sources from atmospheric CO$_2$. Macroalgae (seaweed) can be cultivated in aquaculture farms and collected through mechanical devices; the macroalga selected for this study is Macrocystis pyrifera, a giant brown seaweed characterized by its size and its carbon and oxygen-rich composition. Conventional methods for thermal conversion into potential fuels, such as biomass carbonization, pyrolysis, and gasification are not efficient for biomass with high moisture. For this reason, the research community has introduced new methods like hydrothermal carbonization, liquefaction, and gasification. This project focuses on the process simulation in Aspen plus® V12 to produce green hydrogen from macroalgae biomass by pyrolysis, gasification, and hydrothermal gasification. Hydrogen production was maximized through sensitivity analysis, achieving a hydrogen yield of 2.08% in hydrothermal gasification, 2.06% for pyrolysis, and 1.85% for gasification.

Doctor of Philosophy / Department of Biological and Agricultural Engineering / Wenqiao Yuan / Donghai Wang / Corncobs were used as the feedstock to investigate the effect of operating conditions and crude glycerol (solvent) on bio-oil production. The highest bio-oil yield of 33.8% on the basis of biomass dry weight was obtained at 305°C, 20 min retention time, 10% biomass content, 0.5% catalyst loading. At selected conditions, bio-oil yield based on the total weight of corn cobs and crude glycerol increased to 36.3% as the crude glycerol/corn cobs ratio increased to 5. Furthermore, the optimization of operating conditions was conducted via response surface methodology. A maximum bio-oil yield of 41.3% was obtained at 280°C, 12min, 21% biomass content, and 1.56% catalyst loading. A highest bio-oil carbon content of 74.8% was produced at 340°C with 9% biomass content. A maximum carbon recovery of 25.2% was observed at 280°C, 12min, 21% biomass content, and 1.03% catalyst loading. The effect of biomass ecotype and planting location on bio-oil production were studied on big bluestems. Significant differences were found in the yield and elemental composition of bio-oils produced from big bluestem of different ecotypes and/or planting locations. Generally, the IL ecotype and the Carbondale, IL and Manhattan, KS planting locations gave higher bio-oil yield, which can be attributed to the higher total cellulose and hemicellulose content and/or the higher carbon but lower oxygen contents in these feedstocks. Bio-oil from the IL ecotype also had the highest carbon and lowest oxygen contents, which were not affected by the planting location. In order to better understand the mechanisms of hydrothermal conversion, the interaction effects between cellulose, hemicellulose and lignin in hydrothermal conversion were studied. Positive interaction between cellulose and lignin, but negative interaction between cellulose and hemicellulose were observed. No significant interaction was found between hemicelluose and lignin. Hydrothermal conversion of corncobs, big bluestems, switchgrass, cherry, pecan, pine, hazelnut shell, and their model biomass also were conducted. Bio-oil yield increased as real biomass cellulose and hemicellulose content increased, but an opposite trend was observed for low lignin content model biomass.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / The use of alternative energy sources is a of the major current priorities, that appears to circumvent the serious problems caused by technological development. Accordingly, biodiesel arises as an alternative fuel to petroleum. However, high biodiesel production generates a large quantity of glycerin (10 wt%) which is considered an unwanted byproduct. To increase the market values of the biodiesel byproduct, it is necessary to convert glycerin into other chemicals, such as in lactic acid, which is becoming increasingly important due to their promising polymers applications - eg.: poly(lactic acid) (PLA) - as an alternative to replace petrochemical plastics. In the present study the hydrothermal process was used for lactic acid production, replacing the fermentation process that is currently used to obtain this product. For hydrothermal conversion of glycerol into lactic acid by homogeneous catalysis, NaOH and KOH catalysts were used. And for hydrothermal glycerol lactic acid by heterogeneous catalysis, Cu/SiO2 catalyst was used. Initial glycerol concentration (0.51-17.1 M), temperature (160-280 ÂC), pressure (2-43 bar), water/glycerol volumetric ratio (0.8 to 31), catalyst/glycerol molar ratio (0.01 to 1.02) and total reaction time (3-4 hours) were the variables studied with temperature and water/glycerol volumetric ratio having the major influence. In addition, a first-order kinetic model for glycerol concentration versus time was developed and verified experimentally under conditions with different temperatures. Comparing the results obtained from hydrothermal conversion by homogeneous and heterogeneous catalysis, it was observed that KOH was catalyst with the best performance. The highest yield obtained was 87.5% at 220 ÂC and 28.8 bar, after 3 h, from a solution water/glycerol volumetric ratio equal to 0.8 and KOH/glycerol molar ratio equal to 0.03. From this result, hydrothermal process can be seen as a promising method to add value to glycerol. / A utilizaÃÃo de fontes alternativas de energia à uma das grandes prioridades atuais, que surge para contornar os graves problemas ocasionados pelo desenvolvimento tecnolÃgico. Neste sentido, o biodiesel surge como um combustÃvel alternativo ao petrÃleo. No entanto, a elevada produÃÃo de biodiesel gera uma grande quantidade de glicerina (10% em massa) que à considerada um coproduto. Para aumentar o valor de mercado da glicerina, faz-se necessÃrio convertÃ-la em outros produtos quÃmicos, como por exemplo, em Ãcido lÃtico, que està se tornando cada vez mais importante, devido a aplicaÃÃes promissoras de seus polÃmeros â ex.: poli(Ãcido lÃtico) (PLA) â como uma alternativa para substituir os plÃsticos petroquÃmicos. O presente estudo teve como objetivo utilizar o processo hidrotÃrmico para a produÃÃo de Ãcido lÃtico, em substituiÃÃo ao processo fermentativo que Ã, atualmente, utilizado para a obtenÃÃo deste produto. Para conversÃo hidrotÃrmica do glicerol em Ãcido lÃtico, via catÃlise homogÃnea, NaOH e KOH foram os catalisadores utilizados. E para a conversÃo hidrotÃrmica do glicerol em Ãcido lÃtico, via catÃlise heterogÃnea, Cu/SiO2 foi o catalisador usado. ConcentraÃÃo inicial de glicerol (0,51-17,1 M), temperatura (160-280 ÂC), pressÃo (2-43 bar), razÃo volumÃtrica de Ãgua/glicerol (0,8-31), razÃo molar catalisador/glicerol (0,01-1,02) e tempo total de reaÃÃo (3-4 horas) foram as variÃveis estudadas. A temperatura e a razÃo volumÃtrica de Ãgua/glicerol foram as variÃveis de maior influÃncia. AlÃm disso, um modelo cinÃtico de primeira ordem para determinaÃÃo da concentraÃÃo de glicerol em funÃÃo do tempo foi desenvolvido e verificado experimentalmente em diferentes temperaturas. Comparando os resultados obtidos a partir das conversÃes hidrotÃrmicas, via catÃlise homogÃnea e heterogÃnea, foi possÃvel observar que o KOH foi o catalisador com o melhor desempenho. O maior rendimento obtido foi de 87,5%, a 220 ÂC e a 28,8 bar, em um tempo total de reaÃÃo de 3 h, a partir de uma soluÃÃo de razÃo volumÃtrica Ãgua/glicerina igual a 0,8 e razÃo molar KOH/glicerol igual a 0,03. A partir deste resultado, processo hidrotÃrmico pode ser visto como sendo um processo promissor para agregar valor ao glicerol.

Alkaline industrial wastes are considered potential resources for the mitigation of CO2 emissions by simultaneously capturing and sequestering CO2 through mineralization. Mineralization safely and permanently stores CO2 through its reaction with alkaline earth metals. Apart from natural formations, these elements can also be found in a variety of abundantly available industrial wastes that have high reactivity with CO2, and that are generated close to the emission point-sources. Apparently, it is the applicability and marketability of the carbonated products that define to a great extent the efficiency and viability of the particular process as a point source CO2 mitigation measure. This project investigates the valorization of iron- and steel-making slags through methods incorporating the carbonation of the material, in order to achieve the sequestration of sufficient amounts of CO2 in parallel with the formation of valuable and marketable products. Iron- and steel-manufacturing slags were selected as the most suitable industrial byproducts for the purposes of this research, due to their high production amounts and notable carbonation capacities. The same criteria (production amount and carbonation capacity) were also used for the selection of the iron- and steel-making slag types that are more suitable to the scope of this work. Specifically for the determination of the slag types with the most promising carbonation capacities, the maximum carbonation conversions resulting from recent publications related to the influence of process parameters on the conversion extent of iron- and steel-manufacturing slags, were directly compared to each other using a new index, the Carbonation Weathering Rate, which normalizes the results based on particle size and reaction duration. Among the several iron- and steel-manufacturing slags, basic oxygen furnace (BOF) and blast furnace (BF) slags were found to combine both high production volumes and significant affinity to carbonation. In the context of this research, two different procedures aiming to the formation of value added materials with satisfactory CO2 uptakes were investigated as potential BF and BOF slags valorization methods. In them, carbonation was combined either with granulation and alkali activation (BOF slag), or with hydrothermal conversion (BF slag). Both treatments seemed to be effective and returned encouraging results by managing to store sufficient amounts of CO2 and generating materials with promising qualities. In particular, the performance of the granulation-carbonation of BOF slag as a method leading to the production of secondary aggregates and the sequestration of notable amounts of CO2 in a solid and stable form, was evaluated in this work. For comparison purposes, the material was also subjected to single granulation tests under ambient conditions. In an effort to improve the mechanical properties of the finally synthesized products, apart from water, a mixture of sodium hydroxide and sodium silicate was also tested as a binding agent in both of the employed processes. According to the results, the granules produced after the alkali activation of the material were characterized by remarkably greater particle sizes (from 1 to 5 mm) compared to that of the as received material (0.2 mm), and by enhanced mechanical properties, which in some cases appeared to be adequate for their use as aggregates in construction applications. The maximum CO2 uptake was 40 g CO2/kg of slag and it was achieved after 60 minutes of the combined treatment of alkali activated BOF slag. Regarding the environmental behavior of the synthesized granules, increased levels of Cr and V leaching were noticed from the granules generated by the combination of granulation-carbonation with alkali activation. Nevertheless, the combination of granulation with alkali activation or that of granulation with carbonation were found not to worsen, if not to improve, the leaching behaviour of the granules with regards to the untreated BOF slag. The formation of a zeolitic material with notable heavy metal adsorption capacity, through the hydrothermal conversion of the solid residues resulting from the calcium- extraction stage of the indirect carbonation of BF slag, was also investigated in this project. To this end, calcium was selectively extracted from the slag by leaching, using acetic acid of specific concentration (2 M) as the extraction agent. The residual solids resulting from the filtration of the generated slurry were subsequently subjected to hydrothermal conversion in caustic solution of two different compositions (NaOH of 0.5 M and 2 M). Due to the presence of calcium acetate in the composition of the solid residues, as a result of their inadequate washing, only the hydrothermal conversion attempted using the sodium hydroxide solution of higher concentration (2 M) managed to turn the amorphous slag into a crystalline material, mainly composed by a zeolitic mineral phase (detected by XRD), namely, analcime (NaAlSi2O6·H2O), and tobermorite (Ca5(OH)2Si6O16·4H2O). Finally, the heavy metal adsorption capacity of the particular material was assessed using Ni2+ as the metal for investigation. Three different adsorption models were used for the characterization of the adsorption process, namely Langmuir, Freundlich and Temkin models. Langmuir and Temkin isotherms were found to better describe the process, compared to Freundlich model. Based on the ability of the particular material to adsorb Ni2+ as reported from batch adsorption experiments and ICP-OES analysis, and the maximum monolayer adsorption capacity (Q0 = 11.51 mg/g) as determined by the Langmuir model, the finally synthesized product can potentially be used in wastewater treatment or environmental remediation applications.

Ce travail porte sur l'étude des voies réactionnelles accompagnant la liquéfaction desconstituants de la biomasse lignocellulosique dans un milieu aqueux proche du pointcritique. La stratégie expérimentale consiste à étudier la réaction en unité pilote decomposés lignocellulosiques modèles et à développer une approche analytiquemultitechnique originale afin de caractériser les structures et les masses moléculairesdes produits. Les résultats obtenus montrent que les schémas réactionnels sontcomplexes faisant intervenir de nombreuses voies de fragmentation et de condensationcompétitives. L'étude cinétique à différents temps de séjour montre que la fractionglucidique de la biomasse lignocellulosique a une réactivité très différente de sa fractionligneuse. / This work deals with the study of the reaction pathway during the lignocellulosicconstituent liquefaction by water near its critical point. Experimental method consists ininvestigation of lignocellulosic model compounds conversion in pilot plant combined withdevelopment of a new multitechnique analytical approach in order to characterizeproduct chemical structures and molecular weights. Results show that reaction pathwaysare very complex consisting to several fragmentation and condensation competitivereactions. The kinetic study with different reaction times reveals an important differenceof comportment for the glucidic fraction than the lignin fraction of biomass.

La liqueur noire, sous-produit de l’industrie papetière, est convertie par un processus hydrothermal. Elle a été choisie pour son contenu élevé en eau (80 wt%), matière organique (14 wt%) et minéraux (6 wt%) qui font d'elle une biomasse à haute valeur ajoutée bien qu'encore peu exploitée. L'étude en batch, balayant une large gamme de température (350°C-600°C), permet d'identifier deux flux sortant : une proportion d'hydrogène élevée dans la phase gazeuse (600°C), ainsi qu'une phase solide, appelée coke, générée quelques soient les conditions opératoires utilisées. La génération de solide modifie la composition du milieu réactionnel en procédé batch et peut poser problème en cas de transposition en réacteur continu. Il est donc important de comprendre sa formation pour pallier ces verrous. L'analyse du résidu montre qu'à 350°C, pour des temps de réaction courts (<2h), de microparticules carbonées se forment. Leur taille est influencée par les vitesses de montée et descente en température. Pour des températures plus hautes, le solide ne présente pas d'intérêt morphologique et sa proportion massique augmente avec la température. Ainsi, une production d'hydrogène significative s'accompagnera d'un dépôt solide dans le réacteur. Une étude catalytique a donc été menée en vue d'augmenter la quantité d'hydrogène et de diminuer la formation de coke tout en travaillant à plus basse température. Cette étude, menée à 350°C et 450°C, montre que les réactions d'hydrogénation et d'oxydation mises en jeu par le catalyseur conduisent aux résultats escomptés. La conversion de molécules modèles de la liqueur noire, menée dans les mêmes conditions d'expériences, a permis d'appréhender les mécanismes majeurs mises en jeu lors de la conversion hydrothermale. Les microparticules à 350°C peuvent être valorisées. Cependant, le changement de taille et de morphologie au cours du temps interroge sur la possibilité de passer en réacteur continu. La formation de solide peut être évitée à partir de 450°C en présence de catalyseur, favorisant en parallèle la production d'hydrogène. De ce fait, ce travail de thèse aborde les verrous scientifiques, techniques et technologiques liés à la conversion hydrothermale de la liqueur noire et notamment de la formation du solide, en présence ou non de catalyseur. / Black liquor, a by-product of paper industry, is converted by hydrothermal process. It was chosen for its high water content (80 wt%), organic material (14 wt%) and minerals (6 wt%) that make it a high-value biomass while still untapped. The study in batch, screening a wide temperature range (350°C-600°C), used to identify two outgoing flows: a high proportion of hydrogen in the gas phase (600°C) and a solid phase, called coke, generated regardless the operating conditions used. The generation of solid changes the composition of the reaction medium in batch process and can be problematic in case of transposition in continuous reactor. Thus it is important to understand its formation to overcome these obstacles. Analysis of the residue shows that at 350°C, for short reaction times (< 2h), carbonaceous micro-particles are formed. Their size is influenced by the temperature rates of rise and fall. For higher temperatures, the solid is of no morphological interest and its weight proportion increased with temperature. Thus, a significant production of hydrogen will be associated with a solid deposit in the reactor. A catalytic study was conducted to increase the amount of hydrogen and reduce the formation of coke while working at lower temperature. This study, conducted at 350°C and 450°C, shows that hydrogenation and oxidation reactions involved with the catalyst, lead to the expected results. Converting models molecules of black liquor, conducted with the same experimental conditions, helped to understand the major mechanisms involved during the hydrothermal conversion. The micro-particles at 350°C can be valorized. However, the change in size and morphology over time wondered about the possibility of implement in continuous reactor. The solid formation can be prevented from 450°C in the presence of catalyst, favoring in parallel hydrogen production. Therefore, this thesis deals with scientific, technical and technological locks related to hydrothermal conversion of black liquor and especially the solid formation, with or without catalyst.

Ce travail porte sur la production de bio-huile par liquéfaction hydrothermale de résidus agroalimentaires, réalisée en réacteur batch. L’objectif est d’étudier l’influence des paramètres opératoires sur la production de bio-huile, et de contribuer à la compréhension des mécanismes de conversion hydrothermale de la biomasse. La liquéfaction hydrothermale des résidus agroalimentaires a été étudiée à partir de l’exemple des drêches de cassis, résidus de pressage des baies. Une étude paramétrique a évalué l’influence de la température, du temps de réaction, de la concentration de biomasse et de l’ajout d’hydroxyde de sodium sur le rendement des produits. Cette étude a permis d’identifier des conditions opératoires favorables à la production de bio-huile, dont le rendement peut notamment bénéficier du recyclage de la phase aqueuse en tant que solvant réactionnel (rendement maximal de bio-huile : 31 %). La caractérisation physico-chimique de la bio-huile montre que celle-ci possède certaines propriétés proches du pétrole brut et de certains fiouls lourds, notamment grâce à sa faible teneur en oxygène en comparaison des huiles de pyrolyse. La bio-huile peut être considérée comme un bio-pétrole brut, mais nécessite toutefois un raffinage conséquent avant de potentielles applications. La conversion hydrothermale de molécules modèles, sélectionnées à partir de l’analyse de la composition des drêches de cassis, a été étudiée à une température de 300 °C et un temps de réaction de 60 min. Cinq monomères modèles (glucose, xylose, acide glutamique, guaiacol et acide linoléique) et deux polymères modèles (cellulose microcristalline et lignine alkali) ont été choisis pour cette étude. Une méthodologie basée sur les plans d’expérience de mélange a été mise en œuvre, afin d’aboutir à la construction de schémas réactionnels, et à l’élaboration de corrélations modélisant les rendements des produits en fonction de la composition initiale des mélanges. L’analyse des produits montre que la conversion hydrothermale des résidus agroalimentaires résulte principalement de dégradations primaires et d’interactions binaires entre les composants de la biomasse. Les corrélations obtenues à partir des composés modèles permettent de décrire avec un bon accord les rendements des produits de conversion hydrothermale de mélanges modèles et de plusieurs résidus agroalimentaires : drêches de brasserie, marc de raisin et akènes de framboise. / This work presents a study of hydrothermal liquefaction of food processing residues using a batch reactor, to produce bio-oil. The objective is to study the influence of operating conditions on bio-oil production, and to contribute to the understanding of the reaction mechanisms occurring during hydrothermal conversion of biomass. Hydrothermal liquefaction of food processing residues was studied using blackcurrant pomace, a berry pressing residue, as an example. A parametric study evaluated the influence of temperature, holding time, biomass concentration and the use of sodium hydroxide as additive on the yields of products. This study allowed the identification of favorable operating conditions to produce bio-oil. The bio-oil yield can in particular benefit from recycling the aqueous phase as reaction solvent (maximum bio-oil yield: 31%). Physicochemical characterization of the bio-oil showed that it has some similarities with heavy crude oil and heavy oils, especially thanks to a lower oxygen content than pyrolysis oils. The bio-oil can be considered as a bio-heavy crude oil, but it still requires significant upgrading before any potential applications. Hydrothermal conversion of model molecules, selected from the characterization of blackcurrant pomace, was studied at a temperature of 300 °C and a holding time of 60 min. Five model monomers (glucose, xylose, glutamic acid, guaiacol and linoleic acid) and two model polymers (microcrystalline cellulose and alkali lignin) were chosen for this study. A mixture design of experiments methodology was followed, to combine reactivity studies with the elaboration of correlations describing the mass yields of products as a function of the initial mixture composition. Analysis of the products shows that hydrothermal conversion of food processing residues is mainly due to degradations of individual compounds and binary interactions between components of biomass. The correlations obtained from the model compounds describe with good accuracy the mass yields of the products from hydrothermal conversion of a model mixture and several food processing residues: brewer’s spent grains, grape marc and raspberry achenes.

In a worldwide context where the community has to make giant leaps forward to contain the catastrophic consequences of climate change, we need to face the discordant “How do we power our economies?” with green and circular solutions instead of hiding behind the hypocrisy of fossil fuels. Biomass, renewable, abundant, and cheap, can trigger a shift towards a zero-carbon emission economy, in which it substitutes fossil fuels for the production of energy and materials. Among the strategies to valorize biomass, hydrothermal processes are green pathways for producing biofuels and bio-based materials. However, research has yet to fill several gaps to make these processes ready for industrial scaling and spreading. Therefore, along with this Ph.D. thesis, we provide new insights into hydrothermal processes, touching several scientific areas: from in-depth research around the thermochemical fundamentals to the engineering of new sustainable and biorefinery concepts. Through fundamental research, we try to answer “What’s happening during hydrothermal processes?” facing the enormous complexity of the process by investigating chemical pathways, kinetics, and thermodynamics. Facing sustainability, we explored the coupling of hydrothermal conversion with concentrated solar energy to develop a zero-energy process and the integration of hydrothermal carbonization with subsequent treatments to valorize by-products.