The aim of the work was to examine microalgae growth and nutrient elimination in various diluted digestates in the first trial, then to study CO2 removal from a simulated biogas mixture by the same strain in the second trial. Scenedesmus SCCP K-1826 was cultivated in the digestate from Sundet biogas plant diluted 10, 20 and 30 times. The cultures were open-air with occasional CO2 injections to control pH. On day 15, the best growth was obtained in the 10 times diluted sample. COD, TN and TP removal efficiencies were similar in each bottle as the strain didn’t perform better in any specific dilution. The control proved that additional mechanisms other than photosynthesis contributed to digestate cleaning. Using the 10 times diluted sludge, Scenedesmus was grown in sealed flasks filled with simulated biogas (35.3 % CO2 + 32.3 % CH4 + 32.3 % N2). More algal biomass was produced in this batch culture. Nutrient removal efficiencies were close to the ones reached in the open-air flasks. After 10 days, 96 % of carbon dioxide was reduced. Methane content was depleted as well, possibly due to undesirable methane oxidizing bacteria which infiltrated the medium.

A range of porous solid adsorbents were synthesised and their ability to separate and capture carbon dioxide (CO2) from gas mixtures was examined. CO2 separation from flue gas – a type of exhaust gas from fossil fuel combustion that consists of CO2 mixed with mainly nitrogen and biogas (consists of CO2 mixed with mainly methane) were explicitly considered. The selected adsorbents were chosen partly due to their narrow pore sizes. Narrow pores can differentiate gas molecules of different sizes via a kinetic separation mechanism: a large gas molecule should find it more difficult to enter a narrow pore. CO2 has the smallest kinetic diameter in zeolites when compared with the other two gases in this study. Narrow pore adsorbents can therefore, show enhanced kinetic selectivity to adsorb CO2 from a gas mixture. The adsorbents tested in this study included mixed cation zeolite A, zeolite ZK-4, a range of aluminophosphates and silicoaluminophosphates, as well as two types of titanium silicates (ETS-4, CTS-1). These adsorbents were compared with one another from different aspects such as CO2 capacity, CO2 selectivity, cyclic performance, working capacity, cost of synthesis, etc. Each of the tested adsorbents has its advantages and disadvantages. Serval phosphates were identified as potentially good CO2 adsorbents, but the high cost of their synthesis must be addressed in order to develop these adsorbents for applications. / <p>At the time of the doctoral defence the following papers were unpublished and had a status as follows: Papers 4-8: Manuscripts.</p>

Membrane technology can help alleviate problems of matching supply and demand associated with upgrading on a small-scale level through its flexibility in operation. This paper provides a techno-economic assessment of the use of membrane technology via a quantitative and partial qualitative analysis at farm-based level. The purpose of the analysis is to investigate how the economic and environmental utility of the membranes can be maximised, along with outlining the possible reasons to its lack of diffusion. It combines an applied system research method by way of linear programming with interviews and the use of the innovation-decision process theory. A framework was set out to deliver hard and soft data that could also provide contextual in-depth analysis and discussion. It was found that membranes could provide good compatibility with farm based upgrading systems with desirable outcomes for both an economic and environmental viewpoint. More specifically, upgrading to 80 percent (which is below natural gas standards of 96 percent), was found to be more favourable than to upgrade to 96 percent. However, in addition to much further research and deliberation needed before 80 percent biogas can be used commercially in tractors, the study also outlined priority that needs to be given to the local market demand as well as for the need to introduce closer, more personal engagement with the farmers and make trialing and observing membrane technology better facilitated and funded so as to increase its adoption.

L’épuration est une solution attractive pour la valorisation du biogaz. Néanmoins, les coûts associés à ces procédés constituent un frein au développement, en particulier pour l’épuration du biogaz d’origine agricole.Ces travaux ont évalué le contacteur à membranes, technologie issue du poumon artificiel, pour le développement d’un procédé d’absorption physique, robuste et répondant aux exigences de la filière. Un pilote expérimental modulaire (150-880 NL/h biogaz) a permis d’investiguer les performances du procédé en termes de rendement méthane R_CH4 et de qualité méthane y_CH4,out.Le contacteur à membranes permet de produire un biométhane répondant aux spécifications de l’injection réseau. Les paramètres opératoires clés ont été mis en évidence par un plan d’expérience. Parmi les limites connues du procédé, l’effet de l’humidification de la membrane sur le débit d’absorption du CO2 reste limité (< 10.5%) : une nouvelle description de l’humidification des pores a été proposée. La composition du gaz est plus limitante : le coefficient de transfert du CO2 est divisé par un facteur 2-3 lorsque celui-ci est présent en mélange plutôt qu’en gaz pur. Plusieurs configurations et solvants ont été testés pour améliorer les performances. L’intégration d’une boucle de recyclage et le remplacement de l’eau par une solution de sels (KCl) ont permis de déployer un procédé breveté atteignant les performances visées (R_CH4=98.7%, y_CH4,out=97.5%) : le flux membranaire est de 42 NL/m2/h CO2.En vue d’un dimensionnement industriel, un modèle original de transfert a été développé pour intégrer la géométrie interne spécifique du module membranaire. Optimisé et validé pour l’absorption de CO2 pur, cet outil numérique a nécessité l’optimisation d’une correction additionnelle inspirée des lois de diffusion pour décrire la limite observée en présence d’un mélange de gaz.Une mise à l’échelle est proposée pour 3 unités industrielles (100, 250 et 500 Nm3/h biogaz) sur la base des équipements disponibles. Les dimensionnements obtenus par analyse dimensionnelle ou par modélisation numérique diffèrent de 25 à 40 % et doivent encore être validés. / Upgrading is an attractive pathway for biogas utilization. Yet, the costs associated to these processes are still an obstacle to a widespread development, specifically in the case of farm anaerobic digestion units.This PhD has assessed membrane contactor, a technology derived from the artificial lung, for the development of a robust gas-liquid physical absorption process meeting the biogas industry expectations. A modular experimental pilot (150-880 NL/h biogas) was designed to investigate the performances in terms of methane recovery R_CH4 and methane quality y_CH4,out.The membrane contactor technology turned out to be suitable to produce a gas-grid quality biomethane. Key operating parameters were identified through a Design of Experiments. Among known process limitations, membrane wetting was found to have little influence on CO2 absorption (< 10.5%): a new pore wetting description was suggested. Gas composition was a stronger limitation: the CO2 mass transfer coefficient was divided by a factor 2-3 in the presence of a gas mixture instead of as a pure gas.Process configurations and solvents were successively tested to improve the performances. The addition of a methane recycling loop and the replacement of water by a saline solution (KCl) were combined into a patent and reached the targeted performances (R_CH4=98.7%, y_CH4,out=97.5%): the corresponding absorbed flux is 42 NL/m2/h CO2.For a process upscaling purpose, an original mass transfer model was developed to describe the specific internal geometry of the membrane module. Firstly optimized and validated for the absorption of pure CO2, this numerical tool has required an optimized additional correction inspired from diffusion laws to account for the mass transfer limitation observed for a binary gas mixture.Process designs are suggested for 3 industrial cases (100, 250 and 500 Nm3/h biogas) based on an available membrane contactor range. The process sizings resulting from the dimensional analysis methodology or numerical simulation differ from 25 to 40 % and must then be confirmed.

A geraÃÃo de ResÃduos SÃlidos Urbanos (RSU) vem aumentando a cada ano no PaÃs, sendo a fraÃÃo orgÃnica normalmente responsÃvel por mais da metade da quantidade total de RSU gerada. Entre as alternativas existentes para o aproveitamento dos resÃduos sÃlidos orgÃnicos, destaca-se a digestÃo anaerÃbia, uma soluÃÃo atrativa, tendo em vista que hà produÃÃo de biogÃs durante o processo. Entretanto, para que suas possibilidades de aplicaÃÃo sejam mais abrangentes, à necessÃrio que o biogÃs seja purificado e posteriormente submetido a um processo de upgrade, a fim de que adquira caracterÃsticas similares ao do gÃs natural. O presente trabalho teve como objetivo sintetizar Carbonos Ativados (CAs) a partir de endocarpo de coco seco (Cocos nucifera), de coco babaÃu (Orbignya speciosa) e a partir de vagem de flamboyant (Delonix regia) por meio de ativaÃÃo com diÃxido de carbono em Ãnica etapa. As caracterÃsticas texturais das amostras foram determinadas por meio de isotermas de adsorÃÃo de N2 a -196 ÂC. Os maiores valores de Ãrea superficial especÃfica e volume de microporos foram obtidos para o bioadsorvente sintetizado a partir do coco seco, com valores de 1452 m2/g e 0,60 cm3/g, respectivamente. Foram selecionados os CAs de coco seco e de coco babaÃu para a anÃlise de suas eficiÃncias na separaÃÃo de misturas CO2/CH4 para aplicaÃÃo no upgrade de biogÃs. Para tanto, ensaios de equilÃbrio de adsorÃÃo dos componentes puros (CO2 e CH4) e da mistura (30% vol. CO2, 70% vol. CH4) foram realizados a 20 ÂC utilizando uma balanÃa de suspensÃo magnÃtica. A capacidade de adsorÃÃo de CO2 pouco se diferenciou entre as duas amostras, apresentando o CA de coco seco melhores resultados. Essa amostra apresentou valores bem maiores de captura de metano a pressÃes acima de 3,0 bar. Os dados experimentais foram comparados com os obtidos pelo ajuste do modelo de TÃth e da IAST (Teoria da SoluÃÃo Adsorvida Ideal) para os dados mono e multicomponentes, respectivamente. Os ajustes de TÃth foram bastante precisos, enquanto os da IAST se adequaram moderadamente. As seletividades das amostras para o CO2 em relaÃÃo ao CH4 foram determinadas e comparadas com a de outros adsorventes comerciais. O CA do coco seco apresentou resultados melhores que o coco babaÃu a baixas pressÃes, com valor de seletividade de 4,2 a 1,0 bar, indicando ser um material competitivo para a aplicaÃÃo proposta. / The generation of Municipal Solid Waste (MSW) is increasing every year in Brazil, being the organic matter responsible for more than half of the total MSW generated. Among the current alternatives to the use of organic solid waste, the anaerobic digestion is the most attractive as biogas production occurs in the process. Nevertheless, to increase its usage possibilities, biogas has to be purified and upgraded, in order to acquire characteristics similar to that of natural gas. The present work aims to prepare activated carbons (ACs) from coconut endocarp (Cocos nucifera), babassu coconut (Orbignya speciosa) and flamboyant pods (Delonix regia) by one step CO2 activation. The textural characteristics were determined by N2 adsorption isotherm at -196 ÂC. The best results of BET surface area and micropore volume were obtained for bioadsorbent synthesized from coconut shell, with values of 1452 m2/g and 0.6 cm3/g, respectively. ACs from coconut shell and babassu coconut were selected to analyze their efficiency in CO2/CH4 separation mixture for biogas upgrading application. Therefore, pure component (CO2 and CH4) and mixture (30% vol. CO2, 70% vol. CH4) adsorption equilibria were performed at 20 ÂC using a magnetic suspension balance. The CO2 adsorption capacity slightly differed between samples, presenting the AC from coconut shell better results. This sample had higher methane uptake above pressures of 3.0 bar. The experimental data were compared with the fit of Toth and IAST (Ideal Adsorbed Solution Theory) models for mono and multicomponent data, respectively. The Toth fitting was fairly accurate, while the IAST fit was moderate. The samples selectivity to CO2 over CH4 were calculated and compared with another commercial adsorbent. The AC from coconut shell presented better results than babassu coconut at low pressures, with a selectivity value of 4.2 at 1.0 bar, indicating to be a competitive material for the proposed application.

Bioenergy contributes significantly towards the share of renewable energies, in Europe and worldwide. Besides solid and liquid biofuels, gaseous biofuels, such as biogas or upgraded biogas (biomethane), are an established renewable fuel in Europe. Although many studies consider biomethane technologies, feedstock potentials, or sustainability issues, the literature on the required legislative framework for market introduction is limited. Therefore, this research aims at identifying the market and legislative framework conditions in the three leading biomethane markets in Europe and compare them to the framework conditions of the top six non-European biomethane markets. This study shows the global status and national differences in promoting this renewable energy carrier. For the cross-country comparison, a systematic and iterative literature review is conducted. The results show the top three European biomethane markets (Germany, United Kingdom, Sweden) and the six non-European biomethane markets (Brazil, Canada, China, Japan, South Korea, and the United States of America), pursuing different promotion approaches and framework conditions. Noteworthy cross-national findings are the role of state-level incentives, the tendency to utilise biomethane as vehicular fuel and the focus on residues and waste as feedstock for biomethane production. Presenting a cross-country comparison, this study supports cross-country learning for the promotion of renewable energies like biomethane and gives a pertinent overview of the work.

Im Rahmen der vorliegenden Arbeit wird die CH4-Oxidation an LaFeO3-Katalysatoren unter CH4-reichen und O2-reichen Reaktionsbedingungen betrachtet. Durch Analyse der Struktur-Aktivitätsbeziehungen wird gezeigt, dass eine Kombination von hoher BET-Oberfläche und großer Anzahl an 6-fach von Sauerstoff koordinierten perowskitischen Fe3+-Spezies für eine hohe CH4-Oxidationsaktivität vorteilhaft ist. Mit dem aktivsten LaFeO3-Perowskit kann Sauerstoff unter technisch relevanten Bedingungen bereits bei Temperaturen unterhalb von 350 °C vollständig aus Biogas entfernt werden. Mit einem auf dem Langmuir-Hinshelwood-Mechanismus basierenden kinetischen Modell kann die Methanoxidation unter CH4-reichen Bedingungen erfolgreich simuliert werden. Weiterhin kann der aktivste LaFeO3-Katalysator unter O2-reichen Bedingungen zur Oxidation von Formaldehyd im Abgas magerer Gasmotoren im Temperaturbereich von 350 bis 500 °C eingesetzt werden.:1. Einleitung und Problemstellung 1 2. Einführung in die Literatur 5 2.1. Die Perowskitstruktur 5 2.2. Verwendung von Perowskiten als Katalysatoren 7 2.2.1. CH4-Oxidation 7 2.2.2. CO-Oxidation 12 2.2.3. Oxidation weiterer Kohlenwasserstoffe 14 2.2.4. Minderung von Stickoxiden 16 2.2.5. Weitere katalytische Anwendungen 17 2.3. Katalytische CH4-Oxidation an Edelmetallkatalysatoren 18 2.4. Reaktive Sauerstoffspezies von Perowskitkatalysatoren 20 3. Experimenteller Teil 22 3.1. Synthese von LaFeO3-Katalysatoren 22 3.1.1. PVA-Synthese 22 3.1.2. Citratsynthese 23 3.1.3. Pechini-Synthese 24 3.1.4. NH3-Selbstverbrennung 24 3.1.5. Glycinselbstverbrennung 25 3.1.6. Herstellung von Granulaten 25 3.1.7. Herstellung beschichteter Wabenkatalysatoren 26 3.2. Verwendete Laborapparatur 27 3.3. Charakterisierung der Katalysatoren 28 3.3.1. N2-Physisorption 29 3.3.2. Temperaturprogrammierte Desorption von NH3 30 3.3.3. Temperaturprogrammierte Reduktion mit H2 31 3.3.4. Röntgendiffraktometrie 33 3.3.5. Mößbauerspektroskopie 34 3.3.6. Röntgenphotoelektronenspektroskopie 35 3.4. Katalytische Untersuchungen 36 3.4.1. CH4-Oxidation an LaFeO3-Pulverkatalysatoren im CH4-Überschuss 36 3.4.2. Hydrothermale Alterung des aktivsten LaFeO3-Katalysators 39 3.4.3. Experimentelle Untersuchungen zum Isotopenaustausch mit 18O2 39 3.4.4. Katalytische Aktivitätsmessungen unter sauerstoffreichen Reaktionsbedingungen 41 3.4.5. Testung beschichteter Waben unter sauerstoffreichen Reaktionsbedingungen 42 3.4.6. Untersuchungen zur Verweilzeitverteilung 43 4. Auswertung und Diskussion der Ergebnisse 45 4.1. CH4-Oxidationsaktivität und physikalisch-chemische Eigenschaften der mittels verschiedener Synthesetechniken hergestellten LaFeO3- Katalysatoren 45 4.2. Struktur-Aktivitätskorrelation der mittels Citratsynthese hergestellten LaFeO3-Katalysatoren 49 4.3. Einfluss der Substitution von La durch Ce oder K auf die CH4- Oxidationsaktivität von LaFeO3-Katalysatoren 68 4.4. Einfluss der Raumgeschwindigkeit auf die CH4-Oxidationsaktivität des aktivsten LaFeO3-Katalysators 79 4.5. Einfluss des O2- und CH4-Gehalts im Gasstrom auf die CH4- Oxidationsaktivität des aktivsten LaFeO3-Katalysators 81 4.6. Einfluss der hydrothermalen Alterung auf die CH4-Oxidationsaktivität des aktivsten LaFeO3-Katalysators 84 4.7. Isotopenaustausch mit 18O2 87 4.8. Kinetische Modellierung der CH4-Oxidation unter CH4-reichen Bedingungen am aktivsten LaFeO3-Katalysator 95 4.8.1. Formalkinetischer Ansatz 97 4.8.2. Kinetischer Ansatz auf Basis eines Langmuir-Hinshelwood-Mechanismus 103 4.8.3. Vergleich der beiden kinetischen Modelle 110 4.9. CH4-Oxidation an LaFeO3-Katalysatoren im Sauerstoffüberschuss 112 4.10. Kombinierte Entfernung von CH4, CO und Formaldehyd an mit dem aktivsten LaFeO3-Katalysator beschichteten Mullit-Wabenträgern aus dem Abgas von mager betriebenen Gasmotoren 117 4.11. Anwendung des kinetischen Langmuir-Hinshelwood-Modells auf die CH4- Oxidation am aktivsten LaFeO3-Katalysator unter O2-reichen Reaktionsbedingungen 123 5. Zusammenfassung und Ausblick 130 6. Literaturverzeichnis 134 7. Verzeichnis der verwendeten Formelzeichen 145 8. Anhang 148

La produzione di biogas è un tematica di forte impatto globale per due ragioni principali: il prossimo esaurimento dei combustibili fossili e l’inquinamento ambientale dovuto allo smaltimento di scarti organici. La Digestione Anaerobica (DA) è un processo biologico che permette la risoluzione di entrambi i problemi, producendo energia (in forma di biogas) e convertendo gli scarti organici in metano e anidride carbonica. Tale processo è basato su una complessa catena sintrofica tra consorzi microbici che produco il substrato per la fase finale di metanogenesi. Il siero di latte è uno scarto altamente inquinante derivante dal processo di lavorazione del formaggio e per questo è stato ampiamente investigato come substrato per la DA. Tuttavia esiste uno scarto meno noto prodotto dalle fasi di porzionatura e grattugia del formaggio a lunga stagionatura. Il presente studio analizza il microbioma di digestori anaerobici processanti scarti dell’industria lattiero-casearia, quali letame bovino, siero di latte e scarto del formaggio a pasta dura. In particolare, viene analizzato l’effetto dei parametri di processo, delle diverse configurazioni dei reattori e del tipo di scarto, su tale microbioma. L’obiettivo è raggiunto tramite tecniche biomolecolari che permettono di quantificare e identificare le principali specie presenti nei reattori, insieme alla differente espressione genica in seguito all’iniezione di idrogeno a scopo di upgrading del biogas. / Biogas production is a hot topic, which has globally gained interest from many researchers over the past years. This fact is mainly due to the depletion of fossil fuels and environmental concerns regarding wastes disposal. Anaerobic Digestion (AD) represents a biological way to obtain both energy (in form of biogas) and waste discard, by converting the polluting organic matter. The overall process relies on a syntrophic chain where different microbial consortia produce the feed necessary for the final methanogenic step. Cheese whey has been largely investigated for AD treatment, since is a high polluting waste derived from the cheese-making process. However, there is a less-known waste originating from the portioning and shaving phases of long-ripened hard-cheese. This study aimed to investigate the microbiome of anaerobic digesters processing dairy industry wastes, such as cattle manure, cheese whey and hard-cheese powder wastes. In particular, the effects of process parameters, reactor configurations and type of dairy wastes, on the microbial populations, have been analyzed. The goal was achieved by means of culture-independent methods and high throughput sequencing, which allowed quantifying and identifying the main species present, as well as their differential gene expression in relation to hydrogen injection for biogas upgrading purposes.

The thesis deals with the issue of removing carbon dioxide from biogas using membrane separation. Addresses the impact of the implementation of a small research facility at the existing operation of the biogas plant. Assessment of the impact on traffic is solved in terms of technical and economic.

Strategies to harness the energy from organic waste is gaining importance on a global scale, especially in countries with large quantities of it. In this paper, a techno-economic analysisand a field study were performed to investigate the feasibility of five scenarios for a conceptual biogas facility, based on a case study from Colombia. The plant designs involved anaerobic digestion followed by different combinations of biogas upgrading, combined heat and power and/or steam methane reforming technologies and investigated four different feedstocks. The results demonstrated that the road infrastructure leading to the current proposed site is inadequate, and a new location should be found. Anaerobic digestion alone was most profitable with the shortest payback period. Organic Municipal Solid Waste and Poultry Manure produced high techno-economic potential depending on the scenario. The production of hydrogen using anaerobic digestion, steam methane reforming and combined heat and power with or without upgrading is not recommended due to the current market prices and high heat consumption. However, it can be profitable to implement green energy initiatives as a strategy to establish and lead future energy markets.