Digesters at a biogas plant have high temperatures and poor insulation. There is great potential to save energy by improving the construction. This study has two aims. One is to compare the difference between a simple steady-state calculation and a calculation that uses simulated values from Heat2. The second is to develop an improved insulation method at the concrete digester that can be used in future projects. Ten different insulation scenarios have been simulated to understand how to improve the insulation method to develop an idea of where the insulation has the most impact. Then a combined insulation method was created from the scenarios. That combined method was then simulated with 5 different insulation thickness to find the most profitable design. The conclusion was that there is great value in making more advanced calculations for the walls and floor because the energy losses are very excessive using the simplified calculation, especially on surfaces covered in soil. It was proved difficult to calculate the losses for the roof, this was because the assumption that was needed to perform the calculation does not mirror the reality. Due to this, the roof has been neglected in the suggested insulation method. The insulation method proposed provides an energy saving of 58 MW h/year and a discounted payback time of 4, 3 years if the saved energy can be delivered as 90◦C degree hot water into the district heating network.

There is growing interest in the use of high performance anaerobic digestion (AD) processes for the production of biogas at wastewater treatment facilities to offset the energy demands associated with wastewater treatment. Recuperative thickening (RT) is a promising technique which involves recycling a portion of the digested solids back to the incoming feed. In general there exists a significant number of knowledge gaps in the field of RT because the studies that have been conducted to date have almost exclusively occurred in pilot or full scale trials; this approach greatly limits the amount of process optimization that can be done in a given trial. In this work, a detailed and comprehensive study of RT processes was conducted at the lab scale; a demonstration of the optimization of polymer assisted dewatering is given and biogas production and quality monitored. Two custom designed digesters (capacity = 1.5 L) were operated in parallel with one acting as a ‘control’ digester and the other operating under a semi-batch RT mode; both digesters were also operated in parallel under RT with alternative polymer flocculants. There were no significant changes in the overall biogas methane composition; however the RT digester had an average biogas productivity over two times higher than the control one. It was found that the recycling of the polymer flocculant back into the RT digester resulted in a significant improvement in dewatering performance. At the highest polymer concentration tested, all polymer flocculants demonstrated equivalent dewatering performance achieving over 6 times lower CST’s than the control; at lower polymer concentrations the 4516 polymer flocculant had superior dewatering performance. Thus, there exists an opportunity to decrease the overall consumption of polymer flocculants through judicious selection of the flocculant and the dose that is used both for the thickening and end-stage dewatering processes in RT digesters. / Thesis / Master of Applied Science (MASc) / In wastewater treatment (WWT), solid wastes are treated using a technique called anaerobic digestion (AD) which involves the conversion of solids in biogas by anaerobic bacteria. Biogas is a mixture of mostly methane and carbon dioxide and can be used as a fuel source for energy production. There’s growing interest in the use of high performance AD processes for the production of biogas at WWT facilities to offset the energy demands associated with WWT. Recuperative thickening (RT) is a promising technique which involves recycling a portion of the digested solids back to the digester. In this work, a detailed and comprehensive study of RT processes was conducted at the lab scale; a demonstration of the optimization of polymer assisted dewatering is given and biogas production and quality monitored. Two 1.5 L custom designed digesters were operated in parallel one as a ‘control’ and the other operating under a semi-batch RT.

The world is currently heavily dependent on fossil sources and the use of fossil fuels leads to increased global warming. One of the solutions to this environmental problems is biogas. Biogas is produced through anaerobic digestion of organic material and can be used for electricity or heat production,upgraded and used as vehicle fuel or induced in the industry.Lillerudsgymnasiet is a school that has farm animals, food waste and crop residues. The school is interested in building a small-scale biogas plant for biogas production where they can digest different substrates to produce electricity or heat for their own use.The purpose of this study is to discover the biogas potential during co-digestion of different substrates that are available in agriculture. The goal is to investigate different scenarios to be able to give a recommendation on how Lillerudsgymnasiet should co-digest its substrate in order to optimize its biogas yield.Two different digestion experiments were carried out in an AMPTSⅡ-reactor, where three different cases could be digested per experiment. The substrates were digested in different combinations and the substrates investigated were horse manure with softwood shavings, horse manure with straw, cow manure, pig manure, food waste, silage and crop residues. Samples were also taken for total solids, volatile solids, pH, ammonium, volatile fatty acids and total organic carbon before and after digestion. The amount of methane gas per kilogram substrate and per year was investigated and calculated for the various substrate mixtures.The result shows that the highest methane yield per gram VS (organic material) is obtained when the substrates are mixed and digested based on an optimal C/N value, the yield is then 218 Nml/g VS. The second highest yield is obtained when the substrates are mixed and digested in the same ratio as they are available at Lillerudsgymnasiet and horse manure with softwood shavings has been excluded, the yield is then 216 Nml/g VS. The lowest methane yield per gram VS is obtained when the substrates are mixed and digested in the same ratio as is available at the school but with a maximum amount of horse manure with straw. The methane yield is then 156 Nml/g VS. The result also shows that the highest biogas yield per kilogram of substrate, at Lillerudsgymnasiet, is obtained when the substrates are mixed to obtain an optimal C/N value, the methane gas yield is then 48 NL/kg substrate. The highest amount of methane gas per year, at the school, is obtained when the substrate is digested in the same ratio as is available at the school. The amount of methane gas is then approximately 75,200 Nm3/year.The amount of metals (chromium, copper, zinc, nickel, mercury, cadmium and lead) in the digestate is far below the maximum permitted content for the digestate to be considered suitable as biofertilizer, according to SPCR 120 certification.The result shows that approximately 10% of all manure from horses, pigs and cows in Sweden is digested into biogas, which means that there is a great potential to increase biogas production from agriculture in Sweden. In China, 19% of the biogas production potential is used in rural areas, which shows that there is an opportunity to increase biogas production there as well. In conclusion, Lillerudsgymnasiet is recommended to digest its substrate in the mixture obtained when the C/N content is optimized, if the school can have access to a larger amount of food waste. Otherwise, the substrate should be digested in the ratio it is available at Lillerudsgymnasiet. Finally, the school is recommended to exclude the horse manure with softwood shavings from the decomposition

Greenhouse gas emissions significantly contribute to global warming, seriously threatening our ecosystem. Human civilisation is currently too dependent on fossil fuels and global energy resources that generate greenhouse gasses. A solution can be found in the sustainable development of renewable energy to reduce GHG (greenhouse gas emissions). Biogas production using various digestive materials represents an alternative to fossil fuels. Their replacement with methane gas, GHG emissions, and global warming are environmental factors encouraging the proliferation of the invasive plant species Fallopia japonica, commonly called Japanese Knotweed. This has been recognised as a significant threat to European biodiversity. Controlling this unwanted species is associated with high economic costs. A laboratory study, performed under controlled environmental conditions, was conducted on harvested stems and leaves of the Fallopia japonica plant using different digested matter (DM) to produce biogas energy. The presented study aimed to determine how different DM changed the levels of biogas produced and its methane content. Additionally, the plant material’s capability for regrowth at 37°C in a controlled environment following digestion was investigated. The results demonstrated that Fallopia japonica could be used to produce biogas with high methane concentration. However, the subsequent assessment did not demonstrate regeneration of Fallopia japonica following digestion

Abstrakt   Det förnyelsebara bränslet biogas har fått mer och mer intresse runt om i världen, men för att biogasen ska gå att använda som fordonsbränsle måste den först uppgraderas. I den processen separeras kolväten och andra föroreningar för att metanhalten ska ökas och därmed kommer biogasen att bli optimal för användning i förbränningsmotorer (Enefalk och Ersöz 2016).   Syfte med det här arbetet var att undersöka hur bra olika filter kan fungera för att ta bort orenheter från aminen i Puregas Solutions AB anläggningar. När undersökning av olika filter var gjord studerades underhållet för dessa filter. Experimentet utfördes i Puregas Solutions AB verkstad. Där användes ett aminprov från deras anläggning i Sverige för att den var extremt förorenad och därmed var det lättare att se hur bra de olika filtren filtrerar föroreningar.   Efter att mottagit provsvaren från DOW Chemical Company sammanställdes analyserna. Provsvaren visade på att de testade filtren inte tog bort orenheter från aminen. / Abstract   Renewable biogas fuel has become increasingly interesting around the world, however before biogas is used as fuel in vehicles it must first be upgraded. During that process the hydrocarbons and other pollutions are separated to increase the concentration of methane and make the biogas better suited for combustion engines (Enefalk and Ersöz 2016).   The purpose of this study was to examine how efficiently different filters can remove impurities from amine at Puregas Solutions AB upgrading plant. After the investigation of the different filters was completed we wanted to further study the maintenance of the filters. Experiments were performed at Puregas Solutions AB workshop, where the amine samples from their plant in Sweden were used to see how well the various filters performed.   After receiving the test results from Dow Chemical Company, the results were compiled and they showed that the tested filters did not remove impurities from the amine.

Fossila drivmedel ger en negativ påverkan på miljö och klimat. Men frågan är om biodrivmedel är bättre. Det kan skilja stort mellan olika drivmedel beroende på vilken råvara och framställningsprocess som används. Syftet med studien är att göra en sammanställning av fördelar och nackdelar med olika fossilfria drivmedel som används och kan komma att användas i kollektivtrafiken i Gävleborgs län. I samråd med X-trafik, den regionala kollektivtrafikmyndigheten, har det framkommit att det främst är biodiesel (HVO - hydrogenerade vegetabiliska oljor), biogas och el som är intressanta att analysera. Rapporten kommer att redogöra hur användningen ser ut i andra delar av landet och i världen för att kunna anpassa kunskaperna till Gävleborgs län. I studien ingår även en granskning av produktionspotentialen för dessa drivmedel i länet. Det slutgiltiga resultatet av studien kommer att bidra till utvecklingen av en fossilfri fordonsflotta i regionen. Genom intervjuer med närproducenter av biogas (Gästrike Ekogas AB) och biodiesel (Colabitoil AB) samt med X-trafik inhämtades kunskap om hur produktionen ser ut i länet och vilka behov som finns. Detta tillsammans med en litteraturstudie gav resultatet. X-trafik har huvudansvaret för kollektivtrafiken och utför den genom entreprenörer som fått uppdragen genom upphandling. HVO har många fördelar mot andra dieselbränslen och kan tankas direkt i fordonen utan att dessa behöver modifieras. Dessutom görs den HVO som Colabitoil distribuerar och kommer börja producera på restavfall. En av X-trafiks entreprenörer har slutit ett avtal med Colabitoil vilket betyder att all fossil diesel som bussarna kör på idag kommer att bytas ut mot biodiesel. I Gävle stad kör bussarna på biogas och gasen produceras på avloppsreningsverket Duvbacken. Denna produktion täcker upp 60 % av behovet och resten är fossil gas. Med den nya anläggningen som Gästrike Ekogas håller på att bygga kommer behovet mer än väl täckas upp. Biogasen är även den gjord på restavfall. I den nya biogasanläggningen kommer de också få en utmärkt biogödsel fri från föroreningar, som kan KRAV-märkas och användas till odling för att ersätta konstgödsel. Elbussar är något som diskuteras av X-trafik och kan vara bra alternativ på vissa linjer dock är tekniken under utveckling fortfarande och investeringskostnaden är hög. Det finns potential att kollektivtrafiken i Gävleborgs län kan köra på 100 % miljövänligt, hållbara och närproducerade drivmedel inom en snar framtid. / The purpose of this study is to make a summary of the advantages and disadvantages of various non-fossil fuels that are used and can be used in public transport in the county. In consultation with X-trafik, it has emerged that it is mainly biodiesel (in the form of  HVO - hydrogenated vegetable oils), biogas and electricity that are interesting to analyse. The report will describe the use in other parts of the country and the world to adapt the knowledge to the county. The study also includes an investigation of the production potential of these fuels within the county. The final results of the study will contribute to the development of a fossil free fleet in the region. Through interviews with local producers of biogas (Gästrike Ekogas AB) and biodiesel (Colabitoil AB) and X-trafik information was collected about how the production is performed in the county and what the needs are. This, together with a literature review yielded the results. X-trafik has the main responsibility for the public transport and carries it out through contractors with assignments through procurement. HVO has many advantages compared to other diesel fuels and can be refueled directly in vehicles without modifications of these. Additionally, the HVO that Colabitoil distributes and will begin producing is made of residual waste. One of X-Trafik's contractors has signed a contract with Colabitoil which means that all fossil diesel the buses run on today will be replaced with biodiesel. In Gävle city the buses run on biogas and the gas is produced at the sewage treatment plant. This production covers 60% of the need and the rest is fossil gas. The new facility, which Gästrike Ekogas is building, will produce more than the public transport needs. Biogas is also made from residual waste. The new facility will also yield a by-product in the form of an excellent bio-fertilizer free of contaminants that can be KRAV labelled and used for cultivation to replace chemical fertilizers. Electric buses are something that is discussed, and may be a good option on certain routes, however, the technology is still under development and the investment cost is high. There is great potential that the public transport in the county can run on 100% eco-friendly, sustainable and locally produced fuels in the near future.

Text in English / There are limits on performance of processes and reactions set by material balances and by thermodynamics. The interaction of these theoretical limits and how they influence the behaviour of reactions and equipment is of interest to researchers and designers. This thesis looks at the conversion of biomass to gaseous products under various conditions, including a range of temperatures from ambient to 1500 ⁰C and in the presence or absence of oxygen. The limits of performance of the material balance can be represented as an Attainable Region (AR) in composition or extent space; we call this the MB-AR. The MB-AR represents all possible material balances that can be achieved for a given a set of feeds and set of possible products. The dimension of this space depends on the number of independent material balances. The extreme points of the MB-AR are of particular interest as these define the limiting compositions and the edges of the boundary of the MB-AR represent the limiting material balances. The MB-AR does not depend on temperature. The thermodynamic limits of performance of can be represented as an AR in the space of Gibbs Free Energy (G) and Enthalpy (H); this is called the G-H AR. The G-H AR is always two dimensional, no matter what the dimension of the MB-AR. Extreme points in the G-H AR are also extreme points in the MB-AR are; however not all extreme points in the MB-AR are extreme points in the G-H AR. The extreme points in the MB-AR are transformed by calculating G and H of the points at the condition of interest (reaction temperature and pressure). It is then necessary to find the convex hull in G-H space of this set of transformed points which gives us the boundary of the G-H AR. The extreme points in the G-H AR can be associated with material balances and the extreme point with the minimum G represents the global equilibrium or equivalently the most favoured material balance for the system. The edges of G-H AR are defined by the lines between neighbouring extreme points in the boundary of the G-H AR. These edges represent the limiting material balances in terms of defining the extremes of the G and H of the system. The G-H AR depends on the feed and products through the MB-AR, but also depends on temperature (and pressure). The set of points which are extreme points of both the MB-AR and the G-H AR changes with temperature. Geometrically, the transformed set of extreme points for the MB-AR moves in the GH space as temperature is changed and they move at different rates. Hence when finding the convex hull in the G-H space of the transformed extreme points of the MB-AR, G-H points become either boundary (extreme) points or move into the convex hull at different temperatures. Thus, the material balance which corresponds to the global minimum in G may change with temperature, as do the material balances which are associated with the edges of the G-H AR. Experiments are performed on biomass anaerobically at ambient temperature using microbes as the catalyst, and the products of this process are called biogas. The experiments were performed in a nitrogen plasma system on biomass at higher temperatures (400 ⁰C to 1000 ⁰C) also in the absence of oxygen, and this process would typically be referred to as pyrolysis. Oxygen was added to the plasma system and operated at temperatures between 700 ⁰C and 900 ⁰C, and this would typically be referred to as gasification. Thus, it was able to change the MB-AR by presence or absence of oxygen. By changing operating temperatures, the G-H AR is effectively changed with either the same or different MB-AR’s. The experiments show that in all cases, the product tends towards minimum G. Although this might not be surprising at the higher temperatures, minimizing G is not thought to be the driving force in microbial systems. An important insight from this is that if one were to try and make hydrogen only in a biological system, the system would need to have organisms that make hydrogen only. This is because the material balance that produces hydrogen has a lower change in G than the material balance that make methane. Thus, if there was a consortium of organisms and some of them could make methane, the methane producing organisms would dominate as they have the higher Gibbs Free Energy driving force. If the boundary of the G-H AR around the minimum G is fairly flat, or if many of the extreme points of the MB-AR lie close to the minimum G in the boundary of the G-H AR, then there are many material balances that will give the same G and H. Thus, there are a range of compositions with similar G and H and how one approaches the minimum G will determine the chemical composition of the product. This has important implications for the design, scale up and operation of equipment if a particular product is desired rather process efficiency. The low temperature anaerobic route to gasifying waste, using microbes as catalysts, has a very simple G-H AR, and the preferred products are CH4 and CO2, known as biogas. These units should be relatively stable to operate as none of the other products have G’s that are as negative as that of the biogas. Although not part of this thesis, small-scale anaerobic digesters were installed in communities and these do run easily and stably with fairly little intervention from the operator which seems to support our conclusion. We however could ask, why then have simple technologies, such an anaerobic digestion, not been widely adopted in Africa? To this end we worked with communities and spoke to people about their knowledge about the technology, their concerns and their possible interest in using new approaches to supply energy for cooking and lighting. We found that people were not aware of the technology but would be very interested in adopting a technology that supplied energy cheaply. To our surprise however, their major concern was around hygiene and safety, in that if the gas was made from “poo” how could the gas be clean and would cooking with it not contaminate the food and make people sick? This in hindsight is a very reasonable concern, although it had never occurred to us that this would be a perception. Engineers will have to work with social scientists and psychologist, amongst others, to address the concerns and needs of communities in order for sustainable technologies to be successfully adopted by communities. In summary, this thesis presents a tool for analysing biomass conversion to gaseous products in general, whether microbial or thermal. This tool gives insight into what is achievable, what the major factors are that affect the favoured product and how this can be manipulated to improve efficiency from an overall material and energy point of view. / Physics / D. Phil. (Physics)

Driftdata från More Biogas anläggning i Kalmar har sammanställts och analyserats för att föreslå förbättringar i sammansättningen av den inkommande substratmixen för att öka gasproduktionen. C/N kvoten för den inkommande substratmixen är låg då en optimal C/N kvot är mellan 20 till 30. För att få upp den totala C/N kvoten till 15 behövs 27 ton halm i månaden tillsättas och 80 ton för att få upp den till 20. Det är även bra att tillsätta halm från ströbädd eller hönsgödsel som har en hög TS-halt eftersom det finns möjlighet till en ökad VS-belastning i processen.Slakteriavfall gav en positiv effekt på gasproduktionen och efter en jämförselse av två tidsperioder gav resultatet att gasproduktionen ökade med en MWh per ton TS av tillsatt slakteriavfall.Det finns inget tecken på att processen är hämmad av de inhiberande parametrarna eftersom inte gasproduktionen minskade de månader då de inhiberande parametrarna var högre.

A fermentação anaeróbia da matéria orgânica produz uma mistura de gases chamada biogás. Este biogás contém CH4 e CO2 como componentes majoritários. Estes dois compostos são gases de efeito estufa e sua utilização é muito importante do ponto de vista ambiental e econômico. O presente trabalho teve por objetivo produzir gás de síntese (H2/CO), uma matéria prima de alto valor industrial, a partir da reforma oxidativa do biogás com adição de oxigênio (1,5CH4+1,0CO2+0,25O2) sobre catalisadores de NiO-MgO-ZrO2 e NiO-Y2O3-ZrO2. Os catalisadores foram preparados usando o método de polimerização numa única etapa e foi estudada a variação do teor de MgO e de Y2O3 contido nas amostras. Estes materiais foram caracterizados por DRX, RTP, Adsorção-dessorção de N2, XPS, XAS-XANES, MEV e EDX e foram avaliados na reação de reforma oxidativa de um biogás modelo (composição molar:1,5 CH4/1CO2) em presença de oxigênio, a 750&deg;C e 1atm, visando à obtenção de gás de síntese. Os teores de MgO utilizados no sistema NiO/MgO/ZrO2 foram de 0%, 4%, 20%, 40% e 100% em relação ao ZrO2 (os mesmos teores foram utilizados para Y2O3 no sistema NiO/Y2O3/ZrO2) e o teor mássico de Ni foi 20%. As análises de DRX, TPR, XPS confirmaram a formação das soluções sólidas NiO-MgO e MgO-ZrO2 nos catalisadores NiO-MgO-ZrO2, e das soluções sólidas NiO-Y2O3 e Y2O3-ZrO2 nos catalisadores NiO-Y2O3-ZrO2. Estas soluções sólidas juntas, nos correspondentes catalisadores, melhoraram o desempenho catalítico, levando a altos valores de conversão e baixas taxas de deposição de coque. O teor de MgO ótimo foi de 20%mol no sistema NiO/MgO/ZrO2, e de 20% e 40% mol de Y2O3 no sistema NiO/Y2O3/ZrO2. Nos catalisadores NiO-MgO-ZrO2, a solução sólida NiO-MgO favoreceu principalmente a reação de reforma seca do metano (CH4+CO2), enquanto que nos catalisadores NiO-Y2O3-ZrO2 a solução sólida Y2O3-ZrO2 favoreceu principalmente à oxidação parcial do metano (CH4+1/2O2). Os catalisadores Ni20MZ e Ni20YZ apresentaram resultados promissores para a reforma oxidativa de biogás em presença de oxigênio sendo estes catalisadores melhores do que uma amostra comercial de Ni/Al2O3 (20%Ni) testada nas mesmas condições de reação. A razão H2/CO nos produtos das reações sobre os melhores catalisadores foi muito próxima de 1,0; o que permite seu uso direto em diversas reações, como reação de Fischer-Tropsch, síntese direta de dimetil-éter (processo STD) e síntese de formaldeído. / The anaerobic fermentation of the organic material produces a mixture of gases called biogas. This biogas contains CH4 and CO2 as major components. These two compounds are greenhouse gases and their use are very important from the environmental and economic point of view. The present study aimed to produce synthesis gas (H2/CO), a high-value raw material for the chemical industry, from the oxidative reforming of biogas using oxygen (1.5CH4 +1.0CO2+0.25O2) over NiO-MgO-ZrO2 and NiO-Y2O3-ZrO2 catalysts. These catalysts were prepared by the one-step polymerization method. The variation content of MgO and Y2O3 in each catalyst was studied. These materials were characterized by XRD, TPR, adsorption-desorption of N2, XPS, XAS, SEM and EDX; they were evaluated in the oxidative reforming reaction of a model biogas (molar composition: 1.5 CH4/1CO2) in the presence of oxygen at 750 &deg;C and 1atm, aiming to produce synthesis gas.<br /> The content of MgO in the NiO/MgO/ZrO2 system was varied ranging from 0-100% (0%, 4%, 20%, 40% and 100%mol in relation to ZrO2) , the same contents were used for the Y2O3 in the NiO/Y2O3/ZrO2 system. All catalysts had 20% wt of Ni. The XRD, TPR and XPS confirmed the formation of NiO-MgO and the MgO-ZrO2 solid solutions in the NiO-MgO-ZrO2 catalysts; and NiO-Y2O3 and Y2O3-ZrO2 solid solutions in the NiO-Y2O3-ZrO2 catalysts. These solid solutions together, in the corresponding catalysts, inproved the catalytic performance, leading to high conversion rates and low carbon deposition rates. The optimum MgO content was 20mol% for the NiO/MgO/ZrO2 system and 20% and 40mol% of Y2O3 for the NiO/Y2O3/ZrO2 system. In the NiO-MgO-ZrO2 catalysts, the NiO-MgO solid solution promoted primarily the dry reforming reaction of methane (CH4 + CO2), while in the NiO-Y2O3-ZrO2 catalysts, the Y2O3-ZrO2 solid solution primarily favored the partial oxidation of methane (CH4 + 1/2O2). The Ni20MZ and Ni20YZ catalysts showed promising results for the oxidative reforming of biogas in the presence of oxygen; these catalysts being better than a commercial catalysts (Ni/Al2O3; 20%wt Ni) tested under the same reaction conditions. The H2/CO ratio in the reaction products over the best catalysts was very close to 1.0, which allows its direct use in various processes such as Fischer-Tropsch process, Syngas-to-dimethyl-ether process (STD) and in the synthesis of formaldehyde.

L‘objectif de ce travail est d‘étudier le développement d‘une énergie renouvelable, la méthanisation, comme potentiel vecteur de transformation de l‘activité agricole et de son intégration dans les espaces ruraux en Allemagne. Il s‘agit d‘analyser la dimension spatiale de ce changement social. L‘hypothèse centrale consiste à considérer que les modalités du changement sociotechnique qu‘est la transition énergétique dépendent de la manière dont les acteurs, ici principalement des agriculteurs, se saisissent des possibilités offertes par les objets techniques et les politiques publiques. Ces phénomènes sont ici étudiés dans une enquête structurée par l‘association entre les concepts de multifonctionnalité et de capital territorial, portant sur quatre territoires de projet situés en Allemagne. Les enquêtes deterrain démontrent l‘ambivalence des changements agricoles liés à l‘activité de méthanisation, entre le renforcement de l‘intégration agro-industrielle et celui de l‘ancrage territorial des exploitations agricoles. Elles permettent de dresser une typologie de ces formes d‘hybridation. Il a également pu être démontré que cette ambivalence était fortement liée à l‘évolution des politiques publiques. Cependant, elle est également influencée par les types d‘investisseurs ainsi que par les contextes géographiques, dont les acteurs peuvent mobiliser les caractéristiques (dynamiques récessives ou intégration urbaine des espaces ruraux, héritages territoriaux, rapports localisés à l‘énergie). / This research aims at investigating the connections between energy transitions and agricultural transformations through a comparative research focused on four case studies in Germany. The starting point of this inquiry was the ambivalence of these changes. On the one hand, biogas generation tends to reinforce the socio-economic integration of farms intoagro-industrial value chains. On the other hand, this activity could also strengthen the connections with local stakeholders, for example through the implementation of localised heating networks in neighbouring villages or cities. The first aim of this research is to depict these ambivalent agricultural changes, to identify and evaluate key drivers that shape these processes. The main hypothesis of this work is that not only changes in German policies could explain this ambivalence. The various kinds of investors and the individual farmer‘s aims and needs influence the particular ways in which these changesoccur. Finally, the use of resources bounded to specific contexts contributes to shape these changes, but also generate social inequalities. / Das Ziel dieser Arbeit bestand darin, die Auswirkungen der Energiegewinnung durch Biogas auf die Landwirtschaft und die ländlichen Räume anhand einer vergleichenden Studie in vier deutschen Untersuchungsgebieten zu untersuchen. Dafür wurden die Konzepte der landwirtschaftlichen Multifunktionalität und des territorial capital in Verbindung mit der multi-level perspective auf den soziotechnischen Wandel verwendet. Dabei wurde zunächst der Trend zu einer Hybridisierung dieses Wandels herausgearbeitet. Biogas kann die produktivistischen Praktiken der Betriebe verstärken, aber auchabschwächen. Die Untersuchung zeigt, dass diese gegenläufigen Entwicklungspfade gleichzeitig in den landwirtschaftlichen Betrieben ablaufen können. Darüber hinaus belegt diese Arbeit, dass die Entwicklung der Gesetzgebung und auch die Art von Investoren (industrielle oder finanzielle Firmen, landwirtschaftliche Betriebsarten) ebenso wie die lokalen Merkmale (Peripherisierungsprozesse bzw. Bevölkerungsrückgang im ländlichen Raum, Formen des territorialen Erbes— „héritage territorial― — oder eine besondere lokale Geschichte in Bezug auf das Thema Energie) diese ambivalenten Entwicklungspfade beeinflussen können, sobald die Akteure die betreffenden Merkmaleund Ressourcen nutzen. Deshalb kann es zur Entstehung von umweltbezogenen sozialen Ungleichheiten kommen.