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The production of municipal solid waste has continued to grow in recent years. In Italy, municipal solid waste production reaches about 29 million tons per year. The organic fraction of municipal solid waste (OFMSW), which accounts for 30-40% of the total waste, usually undergoes biological treatments such as anaerobic digestion or composting, or is incinerated or landfilled. Biological treatments are considered not economically viable due to the long processing time (20-30 days), while incineration and landfilling are considered as low cost but polluting processes. In contrast, Hydrothermal Carbonization (HTC) is a cost-effective process to treat organic waste especially for the shorter processing time (0.5-8 h) and the possibility to treat directly wet heterogeneous materials. This thesis aims to investigate the potential use of HTC to upgrade OFMSW and other biomasses to biofuels or valuable byproducts. Chapter 1 gives an overview on the state of the art of HTC technology applied to organic wastes, focusing both on mechanisms and on the characteristics of reaction products. Chapter 2 investigates the potential use of HTC to upgrade the organic fraction of municipal solid waste (OFMSW) into biofuel and byproducts. The impact of process conditions (process time, temperature and solid load) on the formation, chemical and energy properties of hydrochar was deeply investigated. To analyze the behavior of hydrochar as a solid biofuel, the combustion (oxidation) of hydrochar and the co-firing (co-oxidation) of hydrochars and coals was also investigated. The results show that, especially at HTC harsher conditions, hydrochar is a “coal-like” material, that can be used as a valuable solid biofuel. The results evidenced that hydrochar is composed of primary char and secondary char. Primary char (non-extractable with organic solvents) has characteristics similar to coal and could be recovered for combustion, while secondary char is an amorphous and more volatile solid, easily extracted with organic solvents, which found possible application as a source of biochemicals and liquid bio-fuel. Chapter 3 investigates the use of HTC as a promising pre-treatment to enhance the biomethane potential during anaerobic digestion of OFMSW. Anaerobic digestion experiments were carried out using the HTC process liquid and the entire HTC reaction mixtures. Results proved that, when compared to the raw OFMSW, the use of HTC liquid and HTC mixture into AD lead to an increase of biomethane production of up to 37% and 363% by volume, respectively. Chapter 4 reports an HTC kinetics study and a kinetic model, which accounted for reactions leading to the production of primary and secondary char, as well as the liquid and gas phases. The model was optimized using experimental data performed on a lignocellulosic feedstock (olive trimmings) and validated on two other types of biomasses (grape marc and Opuntia Ficus Indica) and was used as a reliable tool to predict the carbon distribution among HTC products. In this chapter an in-depth analysis was also carried out to understand the evolution of feedstock characteristics during the heat-up transient phase before reaching the HTC set-point temperature. The results show that during heat up, the feedstock carbonized to a considerable extent at 220-250 °C. Tests clearly show evidence of the transition between thermal hydrolysis and HTC. Chapter 5 presents a study conducted to evaluate the economic feasibility and the detailed energy and cost analyses of a hypothetical HTC plant transforming wet biomass into pelletized dry hydrochar. To achieve these goals, a model was developed on the basis of experimental results obtained previously on two other organic materials (grape marc and off-specification compost). The results show that, when operating the HTC plant with grape marc at the optimal HTC conditions (T=220 °C, t=1 h, dry biomass to water ratio=0.19), the production cost of hydrochar were determined to be 157 €/ton, competitive with the price of wood pellets (150-200 €/ton). This makes HTC a promising process for a large development at the industrial scale.

In the first chapter, we discuss various techniques and strategies used to synthesize lignin-derived functional materials. The transformation of lignin during pyrolysis and hydrothermal carbonization is also reported. Furthermore, current applications and surface properties of lignin-based carbonaceous materials in the fields of catalysis, bio-absorption removal of pollutants, and supercapacitors are summarized. The second chapter focuses on using electromembrane extraction with high performance liquid chromatography (HPLC) for preconcentration and determination of ampicillin residues in cow milk. In the third chapter, step growth polymerization or polycondensation has been used as an efficient pathway to synthesize polymers with high thermal stability. The resulting materials have different industrial applications. For instance, they can be used as coatings or films in industries, where the materials should be stable in very high temperature (above 500 °C).

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Direct carbon fuel cell (DCFC) is a high temperature fuel cell (around 700 "C) that produces electrical energy from the direct conversion of the chemical energy of carbon. DCFC has a higher achievable efficiency of 80% compared to other fuel cells and the corresponding CO2 emission is very low compared to conventional coal-burning power plants. Moreover, a DCFC can use diversified fuel resources even waste material, which is advantageous compared to other types of fuel cells which are limited to specific fuels. DCFCs are still under development due to a number of fundamental and technological challenges such as the efficiency of carbon fuels and the effect of impurities on the performance and lifetime of the DCFC. These are key factors for the development and commercialization of these devices. In this study, three biochars obtained from the pyrolysis of poultry litters (PL) collected from Tunisian and US farmers, were characterized to see whether they can be potential anode fuels for DCFC or not. PL biochars have low fixed carbon contents (19-35 wt%) and high ash contents (32.5-63 wt%). These ashes contain around 40 wt% catalytic oxides for carbon oxidation reaction, however, these oxides have very low electrical conductivities, which resulted in the very low (negligible) electrical conductivity of the PL biochars (7.7x10-9-70.56x10-9 S/cm) at room temperature. Moreover, the high ash contents resulted in low surface areas (3.34-4.2 m"/g). These findings disqualified PL biochar from being a potential anode fuel for DCFCs. Chemical demineralization in the sequence HF/HCl followed by carbonization at 950" C of the PL biochars will result in higher fixed carbon content, higher surface area, and higher electrical conductivities. Moreover, the treated PL biochars would contain a potential catalyst (Calcium in the form of CaF2) for carbon oxidation. All these criteria would qualify the treated PL biochars to be potential fuels for DCFC. / Master of Science

Phytomining is a promising method for metal recovery, but rare studies have been devoted to metal recovery from hyperaccumulator biomass. The objective of this study was to propose efficient and sustainable methods for treating REE hyperaccumulators, aimed at enhancing REE recovery and obtaining value-added byproducts. Firstly, grass seeds fed with a solution containing Y, La, Ce, and Dy, were found to have the capacity to accumulate around 510 mg/kg (dry basis) of total rare earth elements (TREEs) in grass leaves. With the use of conventional hydrometallurgy, around 95% of Y, La, Ce, and Dy were extracted from the GL using 0.5 mol/L H2SO4 at a solid concentration of 5 wt.%. Subsequently, microwave-assisted hydrothermal carbonization (MHTC) was used to convert the leaching residue into hydrochar to achieve a comprehensive utilization of GL biomass. Scanning electron microscopy (SEM) analysis revealed that the original structure of GL was destructed at 180 °C during MHTC, producing numerous microspheres and pores. As the reaction temperature increased, there was a concurrent increase in carbon content, HHV, and energy densification, coupled with a decrease in hydrogen and oxygen contents of hydrochar. The results showed that the waste biomass of the GL after REE extraction can be effectively converted into energy-rich solid fuel and low-cost adsorbent via MHTC. In addition to utilizing conventional hydrometallurgy for REE recovery and employing MHTC to convert leaching residue into hydrochar, MHTC was also applied to directly recover REEs and produce hydrochar from the GL as a more efficient approach. The effects of acid type and acid concentration on REE extraction from GL using MHTC were investigated. The utilization of 0.2 mol/L H2SO4 led to the extraction of nearly 100% of REEs from the GL into the resulting biocrudes. Concurrently, the acid-mediated MHTC system also caused the degradation of amorphous hemicellulose and crystalline cellulose present in the GL, thereby enhancing the thermal stability of the resulting hydrochar. The physiochemical properties of the hydrochar were also influenced by acid type and acid concentration. Using 0.2 mol/L H2SO4 as the reaction medium, MHTC resulted in a yield of 28% hydrochar with enhanced high heating value and energy densification. These results suggest that MHTC in the presence of an appropriate concentration of H2SO4 is an effective way to extract REEs and produce hydrochar from the GL. A process that combines solvent extraction and struvite precipitation was developed for the treatment of biocrudes containing REEs and other elements. In the extraction step, 95.6% of REEs were extracted using 0.05 mol/L di(2-ethylhexyl)phosphoric acid (D2EHPA) with an aqueous to organic (A/O) ratio of 1:1 at pH 3.0. However, other impurity metals were co-extracted into the organic phase with the REEs. To solve this issue, a subsequent scrubbing step using deionized water was applied, with the removal of over 98% of these impurities, while incurring negligible loss of REEs. After the scrubbing step, over 97% of REEs were ultimately stripped out from the organic phase as REE oxalates using 0.01 mol/L oxalic acid. Furthermore, phosphorous (P) was found to be retained in the raffinate after the solvent extraction process. 94.4% of the P was recovered by forming struvite precipitate at pH 9.0 and a Mg/P molar ratio of 1.5. In general, high purity and value-added REE products and struvite precipitate were eventually achieved from biocrudes in environmentally friendly and economically viable ways. In summary, this study contributes a sustainable and efficient framework for REE hyperaccumulator treatment that integrates acid leaching, MHTC, solvent extraction, and struvite precipitation. This work supports a circular economy, minimizing waste and promoting resource reuse. / Doctor of Philosophy / Rare Earth Elements (REEs) are essential for technologies like smartphones and electric vehicles, but traditional mining is environmentally harmful and resource-intensive. Innovations are needed to reduce waste and enhance resource reuse. In this study, grass, a natural accumulator, was found to be able to extract REEs from contaminated soils. Nearly all REEs can be recovered efficiently using a mild sulfuric acid solution, and the residual biomass was also transformed into valuable byproducts such as energy-rich solid fuel and low-cost adsorbents. Furthermore, a more sustainable and efficient method, microwave-assisted hydrothermal carbonization, was also investigated to treat grass aiming at recovering REEs and achieving value-added products. High purity REE product and phosphorous-rich fertilizer were finally produced. This method reduces the environmental impact of REE mining, utilizes renewable resources, and cuts costs, thereby supporting economic sustainability. By turning environmental challenges into opportunities, this research highlights how innovative, greener methods can drive a more sustainable future in resource management.

Ce mémoire traite de la carbonisation de différents déchets de biomasse par pyrolyse douce dans une première étape. Dans une seconde étape, les charbons produits ont été activés à la vapeur d'eau. Six essences de bois (charme, chêne, douglas, épicéa de Sitka, hêtre et peuplier) ont été carbonisées et l'activation a été étudiée sur 4 essences (chêne, douglas, épicéa et peuplier). La première partie de ce mémoire consiste en une étude bibliographique sur la biomasse et sa valorisation énergétique, la production de charbons et l'activation. La deuxième partie de ce rapport présente les résultats expérimentaux relatifs à la carbonisation. Lorsque la carbonisation est complète, on peut corréler les principales propriétés physiques des charbons produits à partir des propriétés initiales du bois anhydre. Les modifications anatomiques induites par la carbonisation ont été expliquées à partir de mesures sur un porosimètre à mercure et d'observations au microscope électronique. Dans la troisième partie, les charbons obtenus à partir des 4 essences citées ont été activés à la vapeur d'eau à 800 °C pendant une heure. Les principales propriétés physiques caractérisant les charbons activés ont été déterminées. L'adsorption du phénol en phase aqueuse a été étudiée et les isothermes de sorption à 25 °C ont été décrites. L'étude des transferts de matière a montré que l'adsorption du phénol pouvait être caractérisée par un coefficient global de transfert de matière. Pendant l'adsorption, trois étapes limitantes successives ont été observées pendant lesquelles le coefficient global de transfert de matière est assez constant et dont la valeur est divisée par un facteur 10 à chaque changement d'étape / This report concerns the carbonization of different biomass wastes by soft pyrolysis in a first part. In a second part, the charcoals produced have been activated by water vapor. 6 wood species (ash, oak, douglas, Sitka spruce, beech and poplar) have been carbonized and the activation has been investigated on 4 wood species (oak, douglas, spruce and poplar). The first chapter of this report consists in a bibliographical study on biomass, its energetic valorization, production of charcoals and their activation. The second chapter of this report presents the experimental results concerning the carbonization. When the carbonization is complete, the main physical properties of the charcoals produced can be correlated to the initial properties of oven dry woods. The anatomic changes induced by pyrolysis have been explained from measurements performed on a mercury porosimeter and observations on an electronic microscope. In the third chapter, charcoals produced from the 4 wood species cited have been activated with water vapor at 800 °C during 1 hour. The main physical parameters characterizing the activated carbons have been determined. The adsorption of phenol in an aqueous phase has been investigated and the isotherms of sorption at 25 °C have been described. The study of mass transfers shows that the adsorption of phenol can be characterized by a global mass transfer coefficient. During the adsorption, 3 successive limiting steps have been observed. For each step, the mass transfer coefficient is quite constant but its value is divided by about 10 after each change of step

De acordo com o Plano Nacional de Resíduos Sólidos - PNRS, a destinação de resíduos industriais é de responsabilidade do seu gerador. Serrarias do estado de Roraima enfrentam uma série de dificuldades para cumprimento desta norma, principalmente, pela falta de informações e ausência de estudos que comprovem alternativas viáveis específicas para a região. Sabe-se, contudo, que de uma forma ampla e genérica, alternativas poderiam ser propostas. Dentre elas, a conversão direta dos resíduos para geração de energia e a pirólise visando a produção de carvão vegetal e seus co-produtos. Neste sentido, o objetivo geral deste estudo foi identificar, caracterizar e realizar análises a isto vinculadas, considerando os resíduos madeireiros gerados nas serrarias localizadas no pólo de Rorainópolis, Roraima, Brasil. Foram realizadas aferições da granulometria, umidade, composição química, densidade e poder calorífico do material in natura (CAPÍTULO 1). Ainda sobre este material foram realizadas carbonizações à temperatura de 450°C e 650°C e avaliação do carvão vegetal e gases do processo (CAPÍTULO 2). Além disso, foram avaliadas as características físicas, químicas, energéticas dos resíduos obtidos em diferentes seções das pilhas preexistentes nas serrarias (CAPÍTULO 3). / According to the National Solid Waste Plan - PNRS, a destination of industrial solid waste is responsibility of it generator. Roraima\'s sawmills face a series of difficulties to comply this standard, mainly for lack of studies proving feasible alternatives specific to region. It is known, however, that of broad and generic form can be applied alternatives. Among them, the direct conversion of the waste to the generation of energy and pyrolysis for the production of charcoal and co-products. In this sense, the general objective of this study was to identify, characterize and carry out related analyzes, considering the wood residues generated at sawmills located at the Rorainópolis Timber Hub, state of Roraima, Brazil. The granulometry, moisture, chemical composition, density and calorific value of the in natura material were measured (CHAPTER 1). Carbonisations were also carried out at 450°C and 650°C and charcoal and process gases were evaluated (CHAPTER 2). In addition, the physical, chemical and energetic characteristics of residues obtained in different sections of the pre-existing piles in the sawmills were evaluated (CHAPTER 3).