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Le changement d’occupation des sols contaminés est susceptible de modifier la nature et la quantité des matières organiques du sol (MOS). Les matières organiques sont connues pour avoir un rôle de source trophique pour les organismes des sols et un rôle de ligand vis-à-vis des éléments traces métalliques (ETM) dans les sols contaminés. Des changements de matières organiques dus aux changements d’occupation des sols contaminés peuvent modifier la spéciation des ETM et leur disponibilité. Mais dans ce cas, le rôle de la matière organique dans le déterminisme de la disponibilité des ETM est peu documenté. L’objectif du travail présenté dans cette thèse était de mettre en évidence le rôle des matières organiques dans la disponibilité des ETM, dans le cas de sols agricoles contaminés après un changement de cultures annuelles vers des cultures pérennes à vocation non-alimentaire. Le travail a concerné l’étude de la disponibilité du Cu, Pb, Zn et Cd dans les sols de deux sites différents en texture et en origine de pollution i.e. le site de Metaleurop (Nord de la France) avec des sols limoneux contaminés par des retombées atmosphériques et le site de Pierrelaye (Région Parisienne) avec des sols sableux contaminés par les apports d’eaux usées brutes de la ville de Paris. Le rôle de la matière organique a été étudié en travaillant 1) sur des échantillons de sols sous deux cultures différentes i.e. sous culture annuelle et culture pérenne à vocation énergétique miscanthus depuis trois ans, 2) sur les échantillons de sol avant et après incubation in vitro afin d’accélérer la minéralisation de la matière organique, et 3) sur des échantillons de sol avec et sans matières organiques particulaires (MOP) i.e. les fractions libres des MOS afin de mettre en évidence leur rôle spécifique. Une approche combinée d’évaluation de la disponibilité par des extractions chimiques des ETM et d’étude de la localisation des ETM dans des fractions granulométriques a été utilisée. Les résultats obtenus montrent que l’impact de l’occupation des sols (sous culture annuelle ou pérenne miscanthus) sur la disponibilité des ETM était différent pour les deux sites étudiés. Pour les sols du site de Metaleurop les résultats ont montré que la disponibilité de Cu et Pb diminuait sous miscanthus tandis qu’une augmentation de leur localisation dans les fractions fines était observée. Par contre aucun changement n’a été observé pour Zn ni Cd dans ce site. Au contraire pour les sols sableux riches en matières organiques de Pierrelaye le changement d’occupation a impacté la disponibilité de Zn et Cd tandis que celle de Pb et Cu n’a pas évolué. Les résultats des sols avant et après incubation montrent que l’impact de la minéralisation des MOS sur la disponibilité des ETM était site dépendant pour Pb et Cd alors que l’effet sur Cu et Zn était similaire pour les sols des deux sites. En travaillant sur les sols avec et sans MOP, nous avons pu observer que les MOP en tant que fraction organique libre participaient à la disponibilité des ETM telle qu’étudiée, et que une partie du cuivre lié aux MOP était disponible pour un organisme dans nos conditions. Ces résultats de disponibilités des ETM dans des sols qui varient avec la nature et la quantité des matières organiques sont discutés. / The changes in land use of contaminated agricultural soils are susceptible to modify their trace metal availabilities by changing the quality and quantity of soil organic matter. But the role of soil organic matter in the determinism of trace metal availabilities in contaminated soils is not well known. The objective of the present study was to assess the role of soil organic matter in determinism of trace metal availabilities and their dynamics in contaminated soils varying in their texture and nature of pollution. A strategy of studying Cu, Pb, Zn and Cd availabilities of two sites with different texture and origin of pollution was adopted and the role of organic matter was assessed through; 1) sampling the soils of two parcels at each site with two different land uses i.e. under annual crop and under perennial energy crop miscanthus, 2) changing the soil organic matter of these soils through in vitro soil incubations. A combined approach of chemical metal extractions and metal localization study in different soil size fractions was used. The results of the trace metal availabilities of the soil under miscanthus compared to annual crop soil showed that the influence of changes in organic matter through land use was different at both sites. In the silty clayed soil, the availability of Cu and Pb which are the metals known to be preferentially bound to organic matter was decreased with an increase in their localization in soil finer fractions. In the site with organic matter rich sandy soils the availability of metals which are known to be bound to soil mineral phases i.e. Zn and Cd was changed without a change in their localization. The results of laboratory incubation experiments revealed that the mineralization of soil organic matter affects the trace metal availability in two ways. Cu and Zn availabilities are changed in all soils whatever the texture while Pb and Cd availabilities changed only in sandy soils. This difference of the change of metal availabilities in both cases of organic matter variations i.e. between the soil samples under different land use and in the samples of laboratory incubations can be explained by the fact that the changes in organic matter were not similar in both cases. Our work on the metal enriched particulate organic matter (POM) fractions, the most labile organic matter fractions showed that POM act as source and sink of the metals in our conditions and POM associated copper is bioavailable in liquid medium but its bioavailability is less than the metal added as salt solution. These results, increasing the understanding of the role of soil organic matter in the determinism of trace metal availability in different textured soils, are discussed.

Die anaerobe Vergärung von nachwachsenden Rohstoffen und Gülle zur Biogasproduktion als regenerative Energiequelle erfährt seit einigen Jahren einen erheblichen Boom. Dabei werden in Deutschland in der Regel Nassvergärungs-Biogasanlagen betrieben, in denen kontinuierlich Energiepflanzen und Rinder- oder Schweinegülle gemeinsam eingesetzt werden (Kovergärung). Aber auch die alleinige Nassvergärung von Energiepflanzen ohne Gülle (Monovergärung) ist möglich. Häufig fehlen jedoch belastbare Daten zur Auslegung der Biogasanlage und für die Früherkennung kritischer Belastungszustände. Im vorliegenden Projekt sollen Kenntnisse über die Kinetik der Biogasbildung aus nachwachsenden Rohstoffen in Laborversuchen unter praxisrelevanten Prozessbedingungen gewonnen werden. Über diskontinuierliche Batch-Gärtests lassen sich Biogas- und Methanausbeuten unterschiedlicher Substrate auf einfache Weise ermitteln. Bei einheitlichen Laborbedingungen ist damit eine gute Vergleichbarkeit gegeben. Kontinuierliche Belastungssteigerungsversuche sind hingegen nur als Langzeitversuche möglich. Sie geben jedoch zusätzlich Auskunft über den Einfluß der täglichen Belastung des Biogasreaktors mit organischer Substanz und erlauben mit Einschränkungen Aussagen über die optimale Betriebsweise. Die Versuche wurden mit Mais, Rüben und Roggen in Form von Silage als Mono- und Kosubstrat in der Mischung mit Rinder- und Schweinegülle bei meso- und thermophilen Temperaturstufen durchgeführt. Die Versuchsergebnisse konnten ein neu hergeleitetes kinetisches Modell weitgehend bestätigen, das den Zusammenhang zwischen Biogasausbeute und Raumbelastung in Abhängigkeit von den substrat- und prozessspezifischen Parametern wie maximal mögliche Biogasausbeute, Zulaufkonzentration, Dichte des Biogases und des Ablaufes sowie Reaktionsgeschwindigkeitskonstante aufzeigt. Dies kann damit Betreibern von Biogasanlagen als Richtlinie für eine stabile Prozessführung mit hoher energetischer Effizienz dienen. / Anaerobic digestion of energy crops for biogas production has attracted much interest in recent years. In Germany, the most common process is the continuous wet-fermentation of energy crops with cattle slurry or pig slurry (co-digestion). But also the digestion of energy crops as single substrate without slurry (mono-digestion) becomes more important. Because of the great diversity of substrates and the danger of an overload of the reactor at the digestion of high-energetic substrates, sufficient experience for energy crops is still missing. This project should investigate the kinetics of biogas production from energy crops in lab-scale experiments. Biogas and methane yield of different substrates can be estimated easily by discontinuous batch-experiments. These experiments allow a good comparability in case of equal conditions. On the other hand, the influence of the reactor performance and the optimal operational mode can be identified only by continuous long-term experiments with loading increase. Therefore, long-term lab-scale experiments were conducted with maize silage, whole-crop rye silage and fodder beet silage as mono-substrate and co-substrate in a mixture with both cattle slurry and pig slurry under mesophilic and thermophilic conditions. For calculation of biogas yield as function of the organic loading rate, a hyperbolic equation was developed on base of a first order reaction rate for substrate degradation. The biogas yield also depends on the corresponding maximum biogas yield, the concentration of volatile solids of the input, the density of the effluent, the density of the biogas and the reaction rate constant which are all substrate- and process-specific. The results of the experiments approve this model and allow an estimation of the parameters. This is helpful as a guideline for a stable and efficient biogas process.

Thesis (Ph.D.)--Mississippi State University. Dave C. Swalm School of Chemical Engineering. / Title from title screen. Includes bibliographical references.

Thesis (Ph.D.)--Mississippi State University. Dave C. Swalm School of Chemical Engineering. / Title from title screen. Includes bibliographical references.

Biofuels have been used as an energy source for heating and cooking since the beginning of time. However, recent changes in the demand for energy, and in particular, renewable energy, have spurred the growth of liquid biofuel industries in developed countries. Many developing countries, including South Africa have the potential to produce biofuels with benefits extending into the economic and social spheres. Despite government commitments and targets, the South African biodiesel and bio-ethanol industries have stalled in the starting blocks. This research aims to assess the reasons why. South Africa does not have the climate to compete with Brazil in bio-ethanol production and the scope for bioethanol is limited by environmental factors. However our neighbours show significantly more promise in this area. Biodiesel production is more likely to be commercially viable due to the country’s ability to grow oil crops and the need for the by-products. Despite the availability of land for cultivation of energy crops, the required technology and suitable infrastructure, progress has been slow. Uncertainty, high risk and misdirected government interventions have hampered investment in the sector and those involved in biofuel projects are very negative about the government’s ability to stimulate the industry. Consequently, they are looking towards importing feedstock material and exporting the biofuel. This will create a limited number of jobs, but will be energy and carbon negative, and will not aid rural development. Currently there is no medium or large scale virgin oil to biofuel producer operating in the country and the start-up dates for projects are beyond 2013. The WVO biodiesel industry has grown rapidly in the last five years but is limited to small scale operators with limited benefit potential. With the exception of Brazil, other world leaders in biofuels are facing heavy criticism and the mechanisms used to initially boost the industry have very limited application in South Africa. The benefits of biofuel production in South Africa are plentiful and align well with social need and development goals. / Thesis (MBA)--North-West University, Potchefstroom Campus, 2013.

Biofuels have been used as an energy source for heating and cooking since the beginning of time. However, recent changes in the demand for energy, and in particular, renewable energy, have spurred the growth of liquid biofuel industries in developed countries. Many developing countries, including South Africa have the potential to produce biofuels with benefits extending into the economic and social spheres. Despite government commitments and targets, the South African biodiesel and bio-ethanol industries have stalled in the starting blocks. This research aims to assess the reasons why. South Africa does not have the climate to compete with Brazil in bio-ethanol production and the scope for bioethanol is limited by environmental factors. However our neighbours show significantly more promise in this area. Biodiesel production is more likely to be commercially viable due to the country’s ability to grow oil crops and the need for the by-products. Despite the availability of land for cultivation of energy crops, the required technology and suitable infrastructure, progress has been slow. Uncertainty, high risk and misdirected government interventions have hampered investment in the sector and those involved in biofuel projects are very negative about the government’s ability to stimulate the industry. Consequently, they are looking towards importing feedstock material and exporting the biofuel. This will create a limited number of jobs, but will be energy and carbon negative, and will not aid rural development. Currently there is no medium or large scale virgin oil to biofuel producer operating in the country and the start-up dates for projects are beyond 2013. The WVO biodiesel industry has grown rapidly in the last five years but is limited to small scale operators with limited benefit potential. With the exception of Brazil, other world leaders in biofuels are facing heavy criticism and the mechanisms used to initially boost the industry have very limited application in South Africa. The benefits of biofuel production in South Africa are plentiful and align well with social need and development goals. / Thesis (MBA)--North-West University, Potchefstroom Campus, 2013.

La tesi ha un filo logico che inizia con la quantificazione e caratterizzazione degli impatti ambientali della produzione del latte. La ricerca prosegue con l'analisi delle opzioni per mitigare questi impatti, tra cui la produzione di biogas da reflui zootecnici. Il passo successivo è stato quello di analizzare la sostenibilità ambientale della co-digestione della biomassa da colture dedicate e reflui zootecnici. La digestione anaerobica dei reflui zootecnici per la produzione di biogas e la sua combustione per produrre energia elettrica è risultata un approccio tecnologico efficace per ridurre le emissioni di gas serra in quanto riduce le emissioni dallo stoccaggio dei liquami e sostituisce la produzione di energia elettrica da combustibili fossili. La produzione di biogas da biomassa da colture dedicate, anche se non fornisce benefici ambientali di per sé, può essere considerata come una opzione per facilitare e incrementare la digestione dei reflui, ma la biomassa da colture dedicate deve essere utilizzato in modeste quantità. I risultati di questa tesi - realizzati utilizzando la metodologia LCA - possono aiutare i responsabili politici nella pianificazione delle misure volte ad aumentare la sostenibilità della produzione del latte e del biogas nelle aziende zootecniche. / The thesis has a logical thread that starts with the quantification and characterization of the environmental impacts of milk production. The research continues with the analysis of the options for mitigating these impacts, among which biogas production from manure results very effective. The next step was to analyse the environmental sustainability of co-digestion of manure and energy crops. The anaerobic digestion of manure to biogas and its combustion to produce electricity resulted as an effective technological approach to mitigate GHG emissions because it reduces the emissions from slurry storage and contributes to the displacement of electricity generation from fossil fuels. Biogas production from energy crops, although not providing environmental benefits per se, may be regarded as an option to facilitate and increase the digestion of manure, if allowed only in small shares. The results of this thesis – achieved using LCA methodology – can assist policy makers in the planning of measures aimed at increasing the sustainability of milk and biogas production from dairy farms.

Thesis (M.E.S.)--The Evergreen State College, 2007. / Title from title screen (viewed 1/24/2008). Includes bibliographical references.