Anaerobic digestion (AD) is a biochemical process consisting of the microbiological conversion of organic materials for the purpose of generating biogas. Biogas is typically composed of 50 to 70% methane (CH4) and 50 to 30% carbon dioxide (CO2) with trace amounts of other compounds. Anaerobic digestion technology is a bioprocessing technology that has the potential to be integrated into an ethanol facility to further capture energy, in the form of methane gas, for use in a combined heat and power (CHP) generator or for integration into the natural gas pipeline grid after undergoing an upgrading process. The most simplistic design of an AD system is the solid state digester (SSD) which is able to process very high solids content materials (greater than 15% solids). A SSD has the potential to be utilized as a manure management system in a beef cattle feedlot and it has the potential to integrate seamlessly into a combined ethanol- feedlot operation to capitalize on the eco-cluster concept in bioenergy production. This thesis investigates the biogas and digestate composition seen from four material blends in a solid-state digester (SSD) system operated as a batch reactor. Wet distiller grains (WDG) from a grain ethanol process and cattle manure were the substrates investigated. To assess the biogas composition the system was operated over a period of time to achieve a quasi steady state within the microbial population to maximize the CH4 concentration in the biogas composition. To assess the robustness of the microbial population within each substrate blend, the biogas concentrations were measured over three cycle periods where a portion of the used substrate was replaced with an equal amount of fresh substrate. The digestate composition was analyzed at the end of each of the cycles and compared with the raw substrate to determine changes in solids and nutrient values. The biogas production calculated in this study determined 0.17, 0.21, 0.18, and 0.12L per gram (VS) within 100% WDG, 75%WDG and 25% manure, 25% WDG and 75% manure and the 100% manure substrate (Group 1 through 4) respectively, averaged over all three digestion cycles. At the end of three cycles of digestion the biogas within the substrate blend containing 25% WDG and 75% manure (Group 3) achieved a measured CH4 concentration of 49% and the biogas within the 100% manure substrate (Group 4) achieved a 59% concentration of CH4. The duration for each of Group 3 and Group 4 to achieve the production of viable biogas was 100 and 90 days of operation respectively. Thus it can be concluded that a SSD system start up duration will be between three and four months in duration. The gas data gathered in this research study indicates Group 3 had the most robust methanogenic culture established as it has the lowest overall N2 and CO2 concentration detected in the biogas, and the most consistent performance of CH4 production during each cycle. The investigation conducted on the nutrient data gathered in this research supports the conclusion drawn from the gas data regarding the overall methanogenic performance of the substrate blends. The nutrient data for Group 3 maintained an average carbon to nitrogen (C:N) ratio of 25:1 over all three digestion cycles. The nitrogen, phosphorous, potassium, and sulphur components of the manure fertilizer value were maintained through the digestion process of this investigation thus typical manure application rate calculations are applicable when field applying digestate.

Anaerobic digestion (AD) is a biochemical process consisting of the microbiological conversion of organic materials for the purpose of generating biogas. Biogas is typically composed of 50 to 70% methane (CH4) and 50 to 30% carbon dioxide (CO2) with trace amounts of other compounds. Anaerobic digestion technology is a bioprocessing technology that has the potential to be integrated into an ethanol facility to further capture energy, in the form of methane gas, for use in a combined heat and power (CHP) generator or for integration into the natural gas pipeline grid after undergoing an upgrading process. The most simplistic design of an AD system is the solid state digester (SSD) which is able to process very high solids content materials (greater than 15% solids). A SSD has the potential to be utilized as a manure management system in a beef cattle feedlot and it has the potential to integrate seamlessly into a combined ethanol- feedlot operation to capitalize on the eco-cluster concept in bioenergy production. This thesis investigates the biogas and digestate composition seen from four material blends in a solid-state digester (SSD) system operated as a batch reactor. Wet distiller grains (WDG) from a grain ethanol process and cattle manure were the substrates investigated. To assess the biogas composition the system was operated over a period of time to achieve a quasi steady state within the microbial population to maximize the CH4 concentration in the biogas composition. To assess the robustness of the microbial population within each substrate blend, the biogas concentrations were measured over three cycle periods where a portion of the used substrate was replaced with an equal amount of fresh substrate. The digestate composition was analyzed at the end of each of the cycles and compared with the raw substrate to determine changes in solids and nutrient values. The biogas production calculated in this study determined 0.17, 0.21, 0.18, and 0.12L per gram (VS) within 100% WDG, 75%WDG and 25% manure, 25% WDG and 75% manure and the 100% manure substrate (Group 1 through 4) respectively, averaged over all three digestion cycles. At the end of three cycles of digestion the biogas within the substrate blend containing 25% WDG and 75% manure (Group 3) achieved a measured CH4 concentration of 49% and the biogas within the 100% manure substrate (Group 4) achieved a 59% concentration of CH4. The duration for each of Group 3 and Group 4 to achieve the production of viable biogas was 100 and 90 days of operation respectively. Thus it can be concluded that a SSD system start up duration will be between three and four months in duration. The gas data gathered in this research study indicates Group 3 had the most robust methanogenic culture established as it has the lowest overall N2 and CO2 concentration detected in the biogas, and the most consistent performance of CH4 production during each cycle. The investigation conducted on the nutrient data gathered in this research supports the conclusion drawn from the gas data regarding the overall methanogenic performance of the substrate blends. The nutrient data for Group 3 maintained an average carbon to nitrogen (C:N) ratio of 25:1 over all three digestion cycles. The nitrogen, phosphorous, potassium, and sulphur components of the manure fertilizer value were maintained through the digestion process of this investigation thus typical manure application rate calculations are applicable when field applying digestate.

Orientador: Roberto de Oliveira Roça / Resumo: O objetivo deste estudo foi determinar a excreção de patógenos e inocuidade da carcaça de bovinos alimentados com diferentes níveis de silagem inoculada de grãos úmidos de destilaria desengordurados (WDG). Um total de 100 bovinos machos não castrados, 50% Angus e 50% Nelore, foram divididos aleatoriamente entre quatro dietas (N = 25) compostas por diferentes níveis de silagem de WDG (0, 15, 30 e 45% da matéria seca dietética). Amostras de fezes foram colhidas por meio de suabe da junção reto anal, 15 dias antes do abate, para determinar as ocorrências e quantificação de Escherichia coli produtora de toxina Shiga (STEC), E. coli enteropatogênica (EPEC) e Salmonella spp. por meio da técnica qPCR. Também foram colhidas, 52 dias antes do abate, amostras de fezes de cada animal do piso do curral, logo após defecação, as quais foram submetidas a análises físico-químicas. Logo após o abate, a ocorrência e a contagem de indicadores higiênicos e sanitários, E. coli não patogênica, coliformes totais e bactérias aeróbias mesófilas, assim como, a ocorrência de STEC, EPEC e Salmonella spp., foram determinados a partir de amostras colhidas por meio de esponja da superfície das carcaças das regiões do coxão, flanco, peito e pescoço. Os resultados quantitativos foram submetidos a análises de variância e os dados binários foram submetidos a análises logísticas com razão de chances. Todas as análises estatísticas foram realizadas no software estatístico SAS 9.4 considerando um nível de signifi... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objective of this study was to determine the pathogen excretion and carcass safety of cattle fed different levels of inoculated silage from degreased wet distillery grains (WDG). A total of 100 male, 50% Angus and 50% Nelore male bulls were randomly divided into four diets (N = 25) composed of different levels of WDG silage (0, 15, 30 and 45% of dietary dry matter) . Stool specimens were collected by rectal anal junction swab 15 days prior to slaughter to determine the occurrences and quantification of Shiga toxin-producing Escherichia coli (STEC), E. coli enteropathogenic (EPEC) and Salmonella spp. by the qPCR technique. Samples of faeces from each animal on the corral floor were also collected, 52 days before slaughter, immediately after defecation, which were submitted to physical-chemical analysis. Immediately after slaughtering, the occurrence and counting of hygienic and sanitary indicators, non-pathogenic E. coli, total coliforms, and mesophilic aerobic bacteria, as well as the occurrence of STEC, EPEC and Salmonella spp., were determined from samples collected by medium of the surface of the carcasses of the regions of the tail, flank, chest and neck. The quantitative results were submitted to analysis of variance and the binary data were submitted to logistic analyzes with odds ratio. All statistical analyzes were performed in SAS 9.4 statistical software considering a significance level of 5%. The results showed that there was no difference between treatments fo... (Complete abstract click electronic access below) / Doutor