La Digestion Anaérobie (DA), ou méthanisation, est un procédé qui permet le traitement de déchets organiques et la production d’énergie renouvelable sous forme de biogaz. La DA par voie sèche permet en particulier la valorisation de substrats solides, offrant plusieurs possibilités aux traitements de résidus d’origine agricole tels les fumiers, des substrats constitués d’un mélange de paille, fèces et urine accumulés dans les litières des étables. Parmi les technologies disponibles en méthanisation, les « leach-bed reactors » (LBRs), constituent une option valide mais toutefois peu connue et peu développée soit au niveau scientifique qu’industriel.Dans le but d’optimiser ce procédé, plusieurs problématiques ont été affrontées : (i) la caractérisation bio-physico-chimique du fumier et du potentiel énergétique exprimé dans un LBR; (ii) l’optimisation de l’inoculation des réacteurs et de la température de digestion ; (iii) la co-digestion du fumier avec un substrat facilement biodégradable et la problématique reliées à la gestion des acides gras volatiles (AGVs) ainsi produits.Les résultats montrent que le fumier est un substrat lentement biodégradable qui nécessite un long temps de digestion. Cependant, il s’agit d’un déchet agricole adapté à la valorisation par méthanisation et dont les rendements de dégradation et de production de méthane en LBRs sont intéressants industriellement. Ce substrat est par conséquent une ressource organique précieuse dans le contexte agricole.Il a été montré que le fumier bovin contient une population méthanogène active capable de démarrer un procédé de digestion anaérobie efficacement sans l’ajout d’un inoculum externe spécifique, autant en mode mésophile que thermophile. Une analyse économique a démontré que cette propriété peut être exploitée afin de diminuer les coûts d’investissement initiaux d’un projet à l’échelle industrielle, en favorisant de cette manière le développement de la filière. De plus, les résultats montrent que pour la digestion du fumier en LBRs le mode thermophile ne comporte aucun intérêt par rapport à la production finale de méthane (qui est similaire pour les deux régimes) et que, au contraire, la valorisation par cogénération du méthane produit en thermophile diminue le rendement de production électrique surtout à cause d’une production de méthane très importante en début de digestion. Le régime mésophile parait donc être le mode de fonctionnement le plus adapté dans ce contexte.Enfin, le rôle joué par la percolation du lixiviat sur la mobilisation des AGV accumulés dans la fraction solide a été mis en lumière dans un réacteur de co-digestion traitant une fraction de lentement biodégradable (le fumier) et une fraction facilement biodégradable. Une stratégie a été développée afin d’étudier le problème de l’extraction et de la consommation des AGV dans le but d’améliorer le rendement global du procédé.Pour conclure, ce travail a permis d’optimiser certains paramètres fondamentaux dans la gestion d’un LBR. Cette technologie s’est révélée efficace dans le traitement du fumier, autant en mono-digestion qu’en co-digestion avec un substrat facilement biodégradable. Ces recherches montrent que l’utilisation des LBR est appropriée au contexte agricole et que la modification des paramètres de contrôle permet à ce procédé de répondre efficacement aux problématiques du terrain. Ce travail représente une avancée significative vers la compréhension et le développement des LBRs pour le traitement des résidus agricole et, plus globalement, des énergies renouvelables mobilisant des biomasses agricoles / Anaerobic Digestion (AD) is a process which allows the treatment of organic waste and the production of renewable energy. In particular, dry AD allows the treatment of solid organic substrates, offering several possibilities to the enhancement of agricultural waste such as spent livestock bedding (a mixture of straw, faeces and urine). Among the available biotechnologies in AD, leach-bed reactor (LBRs) is a promising but yet poorly known process both at scientific and industrial level.In order to develop this process, several issues have been studied: (i) the bio-physico-chemical characterization of spent animal bedding and its digestion potential in LBRs; (ii) the optimization of the start-up and the operating temperature of the digesters; (iii) the co-digestion of spent animal bedding with an easily-degradable substrate and the issues connected to the management of the volatile fatty acids (VFAs) produced.The results showed that spent animal bedding is a slowly-degradable substrate which needs a long digestion time. However, it is a substrate suitable to be treated through AD displaying high degradation and methane production rates when processed in LBRs. This substrate is, therefore, a valuable organic resource in the agricultural context.Spent animal bedding was shown to contain an active methanogenic population able to start the process efficiently, both in thermophilic and mesophilic temperature, without requiring a specific external inoculation. An economic study at industrial scale proved that this peculiarity can be used to diminish the investment costs and then promote the development of this process. Moreover, thermophilic temperature was proved to be less advantageous over mesophilic condition. In fact, despite the very close methane yield reached in both temperature range, the different biogas production rates in thermophilic conditions would lead to a reduction of the final electric energy production in this condition. Mesophilic temperature was then shown to be the best operating condition for this process.Finally, the role played by the leachate recirculation in the mobilization of the VFAs accumulating in the solid bulk was highlighted in the case of a reactor co-digesting slowly- (spent livestock bedding) and easily-degradable substrates. A strategy was even proposed to efficiently face such a problem by optimizing both the VFA extraction and consumption with the objectives of increasing the overall process efficiency.In the end, this work allowed to optimize some important parameters for the correct management of the LBRs. This technology was proved to be efficient in the treatment of spent livestock bedding, both as a sole substrate or in co-digestion with an easily-degradable substrate. This research study demonstrates that LBRs is an adapted process for the agricultural context and this technology can easily answer to the full scale issues usually encountered. This work represents a significant advance towards the comprehension and development of LBRs to treat agricultural waste and, more generally, to the development of renewable energies based on biomass

The Ontario biogas industry is relatively young and the overall objective of this research was to help support the growth of the industry with investigating the use of co-substrates and reactor design to enhance biogas production, recommend guidelines on the operation of full scale systems to optimize performance and characterize digestate quality. Laboratory studies evaluated the use of various substrates in the co-digestion with liquid dairy manure. These studies were used to establish ultimate biogas yields, % volatile solids (VS) reduction and minimum hydraulic retention times (HRTs). Box-Wilson Central Composite design models for corn thin stillage and waste grease (as co-substrates with dairy manure) suggest methane yields optimize with increasing proportion of the feed VS from co-substrates (constant total VS in all assays) and increasing temperatures; however, temperature had a great effect. Bench scale studies were conducted to determine a change in digester design to optimize biogas yields and increase digestate stability. A two-phase digestion system was implemented for co-digestion systems using thin stillage and waste grease with dairy manure, and methane yields showed to increase by over 22% when compared with single-phase systems. Based on current FIT contracts of 18 to 20¢/kWhe, the increased electricity and heat production could make the two-phase system economically attractive for producers. Organic loading rates (OLRs) over 4.4 g VS/L led to digester upset and OLRs of over 4.2 g VS/L·day are not recommended. On-farm anaerobic digester systems were studied for digester performance and digestate quality. Residual biogas potential (RBP) yields were effective at evaluating the stability of digestate and the U.K. PAS 110:2014 limit of 0.45 L biogas/g VS (28 days incubation) was assessed too lenient for the Ontario systems studied. A limit of 0.25 L biogas/g VS after 28 days of incubation or 0.45 L biogas/g VS after 60 days of incubation are recommended. VS reductions ranged from 56 to 76% and easily achieved the O. Reg. 267/03 regulated 50% VS reduction. E.coli and Salmonella were typically 1 to 3 logs CFU/100 mL lower than raw manure and increased HRT did not demonstrate a significant impact on the bacterial log reductions. Intermediate alkalinity (IA)/partial alkalinity (PA) proved to be a valuable tool in determining potential digester upset and has been recommended as a standard performance parameter for on-farm systems.

MSCAGR (Soil Science) / Department of Soil Science / Poultry manure (PM) is an inexpensive source of fertilizer but it decomposes quickly and releases carbon and greenhouse gases. Biochar (BC) could be an alternative source of carbon to improve soil quality and reduce greenhouse gas emission. This study investigated the effect of co-application of BC and PM on selected soil physical and chemical properties and performance of maize. A field experiment was conducted at the University of Venda experimental farm during 2015/2016 and 2016/2017 seasons. The experiment was a 4 x 3 factorial arrangement consisting of four rates of BC (0, 5, 10 and 20 t ha-1) and three rates of PM (0, 2, and 4 t ha-1) in a RCBD arrangement replicated three times. Maize was planted in both seasons. After harvest, soil bulk density was determined at four soil depths (0-5, 5-10, 10-15, and 15-20 cm), while aggregate stability and selected soil chemical properties were determined at two soil depths (0-15 cm and 15-30 cm). Data were subjected to ANOVA using Genstat 17th edition. The least significant difference was used to compare the treatment means at P < 0.05. Soil aggregate stability, organic carbon, Ca2+, Mg2+, K+, maize dry matter and maize grain yield increased with increasing rates of BC and PM application at 0 - 15 cm depth in both seasons. The combination of BC at 20 t ha-1 and PM at 4 t ha-1 significantly (P < 0.05) decreased soil bulk density at 5 - 10 cm depth but increased soil available P and total N at the two depths in both seasons. The results of this study suggested that BC and PM improved soil ability to retain and supply nutrients through improved soil aggregate stability and reduced bulk density thereby improving maize dry matter and grain yield. Combining BC with PM proved to enhance the ability of soil to function by improving selected soil physical and chemical properties thereby improving maize dry matter and grain yield. / NRF

Poultry manure is a useful nutrient source but recently it has raised environmental concern due to possible P movement from P saturated soils to waterbodies. This study was conducted to determine the effects of using phytase and high available phosphorous corn diets on the solubility and plant uptake of P, Cu, and Zn in poultry manure and soils amended with manure. Five diet treatments were used in the study: 1) normal phytic acid corn and 0.135% inorganic P (NPA), 2) normal phytic acid corn, 600 units phytase, and 0.135% inorganic P (NPA+Phytase), 3) normal phytic acid corn and 0.345% inorganic P (NPA+P), 4) high available phosphorous corn and 0.135% inorganic P (HAP), 5) high available phosphorous corn, 600 units phytase, and 0.135% inorganic P (HAP+Phytase). The NPA+P diet and NPA+Phytase diets are most similar to the conventional and alternative phytase supplemented diets currently used commercially. Three Virginia soils (Groseclose, Cecil, Mahan) were amended with manure from the diet treatments at rates of 25 and 50 g/kg and P and Cu were extracted with 0.01 M CaCl2 and Mehlich III extractant after incubation periods of 6 and 12 months. Corn was grown in a greenhouse experiment using these same Virginia soils and sand amended with 8.96 Mg/ha poultry manure from each of the five diet treatments. Poultry manure was nonsequentially extracted for determination of P, Cu, and Zn fractions. Comparing the alternative NPA+Phytase, HAP, and HAP+Phytase treatments to the conventional NPA+P treatment on an N- (nitrogen) basis all reduced both CaCl2 and Mehlich III-soluble P concentrations (P<0.05). Comparing these same treatments on a P-basis increased P extracted with CaCl2 24, 26, and 37%, respectively, and P extracted with Mehlich III P 5, 4, and 9%, respectively (P<0.05). The alternative NPA+Phytase and HAP+Phytase treatments increased water-soluble Cu compared to the conventional NPA+P on both a N- and P-basis, while no differences were observed in Mehlich III solubility between these treatments (P<0.05). The alternative NPA+Phytase treatment did not differ in Pand Cu in corn tissue or plant uptake when compared to the NPA or NPA+P (N- or P-basis) treatments. No difference in Zn in corn tissue was observed between these treatments on a N-basis, while NPA+Phytase was higher on a P-basis. Plant uptake of Zn was higher in the NPA+Phytase treatment compared to the NPA+P treatment on both a N- and P-basis. Addition of phytase reduced P solubility from all reagents except for CaCl2 (P<0.05). Replacing the conventional NPA+P treatment for the alternative NPA+Phytase treatment resulted in higher Cu concentrations for all reagents except for K-pyrophosphate and nitric acid. This same replacement increased Zn extracted by water, CaCl2, and CaNO3, while it reduced Zn extracted by HCl, acetic acid, PbNO3, K-pyrophosphate, and NH4-oxalate in the light. The use of phytase decreased P solubility from manure amended soils when treatments are compared on an equal N-basis, and increased P solubility when compared on an equal P-basis. No effect on plant uptake of P or Cu occurredfrom the NPA+Phytase treatment. / Master of Science

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Ammonia emissions from dairy and livestock operations are of significant environmental and human health concern in the United States. Conservation of ammonia from fall surface-applied manure could benefit farmers by retaining nitrogen for use by crops in the spring growing season. The primary goal of this research was to investigate a management strategy for mitigating ammonia volatility from cow manure at the time of field application with no incorporation in the fall before snow fall. The hypothesis is that application of manure in cooler fall temperatures will slow the rate of ammonia volatilization. The objective was achieved by measuring temperature and rates of ammonia volatility from surface-applied liquid dairy manure every month over a period of four months from September to December, 2008. Manure was surface-applied to a field cover-cropped with winter rye (Secale cerealeL.) in September. Ammonia emissions were measured using a dynamic chamber method. Colder temperatures significantly reduced rates of volatility and amounts of nitrate found in the soil. However, N-accumulation in the cover crop fluctuated and was not significantly different from month to month. The greatest spring nitrogen retention and lowest rates of ammonia volatility in the fall were from December plots. Surface application of liquid dairy manure should be conducted as late as possible in the fall before snow fall for the least amount of nitrogen loss due to ammonia volatilization. Planting a cover crop at the time of fall harvest in conjunction with a late fall (November or December) manure application is a nutrient management strategy which deserves further investigation.