Made available in DSpace on 2017-07-10T19:23:38Z (GMT). No. of bitstreams: 1 Taiana.pdf: 1049826 bytes, checksum: 6b4cf77a1f5c7d5f54a87597ae4844ae (MD5) Previous issue date: 2013-04-04 / Sheep litter has in its composition manures incorporated to rice husk, which is a lignocellulosic material. Materials with this characteristic are stabilized for longer period of time and have restrictions on decomposing since they present strong fractions that can, sometimes, be inaccessible to micro-organisms. Some alternatives have been used in order to easy these nutrients recycling, for example its ordinary mixing with another residue. Thus, this essay aimed at evaluating vermicomposting, composting and anaerobic co-digestion applied to sheep litter mixed with cattle manure in order to provide available conditions to change such residues. Three assays were carried out from five ratios of sheep litter and cattle manure: 0:100, 25:75, 50:50, 75:25 and 100:0, which represented treatments T100, T75, T50, T25 and T0, respectively. The process of vermicomposting was carried out from November 2011 to march 2012. The material has undergone a preparation in order to eliminate toxic composts. Then, 0.88 kg of dry mass and 15 adult worms (Eisenia foetida) were allocated in the vermireactor. The ≥ 45% ash content was the stability parameter adopted in this assay. The composting piles were carried out from April to July 2012 in a covered area of concrete floor. Each pile had 200 kg of dry mass and received manual turnings two times a week during the first month and weekly from then on. Composting was supervised until the piles reached values close to room temperature, when the material was stabilized. The experimental period for anaerobic co-digestion occurred from May to October 2012. An entry mixture diluted with water was made in order to obtain a 5% content of total solids. And for residues fermentation, PVC bench scale bio-digesters were used to storage 6 L volume of such material. An anaerobic co-digestion was carried out in a batch system and observed until the curve of biogas production had decreased. In all assays, the adopted experimental design was completely randomized with univariate and multivariate statistics for data evaluation. The results showed that 50% of cattle manure was necessary in the mixture so that sheep litter could be efficiently absorbed in composting and in anaerobic co-digestion. This ratio generated a compost and biofertilizer with greater stability and content of nutrients as well as provided a larger scale of biogas production. In vermicomposting, the sheep litter showed potential to be used in a ratio up to 75% in mixture with cattle manure for Eisenia foetida specie development. However, greater ratios than 25% have decreased the vermicompost quality and in all assays, the rice husk was not transformed. / A cama de ovinos é composta por dejeções incorporadas a um material lignocelulósico, a casca de arroz. Materiais com essa característica apresentam maior tempo de estabilização ou limitações na decomposição, pois são constituídos de frações resistentes, por vezes inacessíveis aos microrganismos. Algumas alternativas são utilizadas para facilitar a reciclagem desses nutrientes, como a simples combinação com outro resíduo. Com este propósito, objetivou-se avaliar a vermicompostagem, a compostagem e a co-digestão anaeróbia de cama de ovinos em mistura com dejetos bovinos a fim de que fossem fornecidas condições adequadas para a transformação dos resíduos. Os três ensaios foram realizados a partir de cinco proporções de cama de ovinos e dejetos bovinos: 0: 100, 25: 75, 50: 50, 75: 25 e 100: 0, os quais representavam os tratamentos T100, T75, T50, T25 e T0, respectivamente. A vermicompostagem foi conduzida de novembro de 2011 a março de 2012. O preparo do material foi realizado a fim de que fossem eliminados os compostos tóxicos. Posteriormente, foram depositados 0,88 kg de massa seca e 15 minhocas adultas da espécie Eisenia foetida nos vermireatores. O conteúdo de cinzas de ≥ 45% serviu de parâmetro de estabilidade adotado neste ensaio. As leiras de compostagem foram conduzidas de abril a julho de 2012, em pátio coberto e com piso em concreto. Cada leira contou com 200 kg de massa seca e foram realizados revolvimentos manuais duas vezes por semana no primeiro mês e semanalmente a partir desse momento. A compostagem foi acompanhada até as leiras apresentarem valores de temperatura próximos a ambiente, quando considerou-se o material estabilizado. Na co-digestão anaeróbia, o período experimental foi de maio a outubro de 2012. A mistura de entrada, diluída com água, foi feita a fim de obter-se o teor de sólidos totais de 5%. Para fermentação dos resíduos, utilizaram-se biodigestores de PVC de bancada com volume útil de 6 L. A co-digestão anaeróbia foi conduzida em sistema batelada e acompanhada até o decréscimo da curva de produção de biogás. O delineamento experimental adotado em todos os ensaios foi inteiramente casualizado, com emprego de análises estatísticas univariadas e multivariadas para avaliação dos dados. Os resultados demonstraram a necessidade de 50% de dejetos de bovinos na mistura, para que a cama de ovinos pudesse ser absorvida eficientemente na compostagem e na co-digestão anaeróbia. Essa proporção deu origem a um composto e biofertilizante com maior estabilidade e conteúdo de nutrientes, além de proporcionar maiores produções de biogás. Em vermicompostagem, a cama de ovinos apresentou potencial de ser utilizada em proporção de até 75% na mistura com dejetos bovinos, para desenvolvimento da espécie Eisenia foetida. Porém, proporções superiores a 25% diminuíram a qualidade do vermicomposto. A casca de arroz não foi transformada em todos os ensaios.

Este estudo investigou a aplicação de um AnSBBR operado de forma descontínua e/ou descontínua alimentada com agitação mecânica, no processo de produção de hidrogênio a partir da codigestão de vinhaça e melaço. O desempenho do processo foi avaliado em função da eficiência de remoção da matéria orgânica, da estabilidade, e dos índices de desempenho referentes à produtividade e ao rendimento molar do hidrogênio e à composição do biogás gerado. Foram avaliadas a influência dos seguintes parâmetros: composição (codigestão com sacarose ou melaço) e concentração afluente, tempo de ciclo, suplementação de micronutrientes (completa/parcial/ausência), tipo de alimentação (batelada/batelada alimentada) e a necessidade do tratamento do inóculo. O sistema estudado se mostrou estável e a codigestão da vinhaça e melaço viável para produção de hidrogênio. Os melhores resultados foram obtidos na condição em que o reator foi operado em batelada (tempo de alimentação 5% do tempo de ciclo), afluente com concentração 6000 mgDQO.L-1 e composição 67% vinhaça e 33% melaço, tempo de ciclo de 3 horas, ausência da suplementação de micronutrientes e foi realizado tratamento térmico do inóculo. Nesta condição a produtividade molar foi de 13,5 mol H2.m-3.d-1 e metano não foi produzido. As demais condições mostraram que o aumento da porcentagem de vinhaça no afluente e a operação em batelada alimentada prejudicaram a produção de hidrogênio. O aumento da concentração da matéria orgânica do afluente, a diminuição do tempo de ciclo, a ausência da suplementação de micronutrientes e a realização do tratamento térmico do inóculo favoreceram a produtividade e rendimento molares de hidrogênio. / A mechanically stirred anaerobic batch and/or fed-batch reactor, containing biomass immobilized on inert support (AnSBBR) was investigated as to its ability to produce hydrogen from the co-digestion of vinasse and molasses. Process performance was assessed in terms of organic matter removal efficiency, stability, and of performance indicators related to hydrogen productivity and molar yield and to composition of the generated biogas. The effects of the following parameters have been assessed: influent composition and concentration (co-digestion with sucrose or molasses), cycle length, micronutrient supplementation (complete/partial/absence), feeding strategy (batch or fed-batch) and need for pre-treatment of the inoculum. The system showed to be stable and the co-digestion of vinasse and molasses showed to be feasible. The best results were obtained at the following conditions: 3-h cycle sequencing batch (feed time equaled 5% of cycle length), influent concentration of 6000 mgCOD.L-1 containing 67% vinasse and 33% molasses, preheating of the inoculum, and with no micronutrient supplementation. At this condition, the molar yield was 13.5 mol H2.m-3.d-1, and no methane was produced. The remaining conditions showed that increase in vinasse content in the influent and fed-batch operation were detrimental to system performance. The increase in organic matter concentration, reduction in cycle length, no micronutrient supplementation and inoculum preheating favored productivity and molar hydrogen yield.

A presente pesquisa teve como proposta avaliar o reator anaeróbio, operado de forma descontínua ou descontínua alimentada, contendo biomassa imobilizada em suporte inerte e com recirculação da fase líquida (AnSBBR) aplicado à produção de biohidrogênio a partir da codigestão de glicerina (efluente da produção de biodiesel) e soro de leite (efluente da produção de laticínios). A estabilidade, os índices de desempenho (referentes à produtividade e rendimento molar do hidrogênio) e o fator de conversão (entre biogás produzido e matéria orgânica consumida) foram analisados em função da composição afluente (porcentagem de cada substrato alimentado ao sistema), da variação da carga orgânica, do tempo de enchimento e da temperatura (20, 25, 30 e 35ºC). Os ensaios foram realizados em diferentes proporções dos substratos utilizando-se variadas cargas orgânicas volumétricas (10,3; 17,1 e 24,0 gDQO.L-1.d-1), as quais foram modificadas em função: (i) da concentração afluente (3, 5 e 7 gDQO.L-1) e (ii) do tempo de ciclo (4, 3 e 2 h, ou seja, 6, 8 e 12 ciclos diários). Também foram realizados ensaios para a produção de biometano a partir da codigestão proposta nesta pesquisa (com COAV de 7,6 gDQO.L-1.d-1) em diferentes proporções de mistura. Para a produção de biometano, a condição com 75% de soro e 25% de glicerina (base DQO) obteve os melhores resultados: produtividade molar de 101,8 molCH4.m-3.d-1 e rendimento por carga aplicada de 13,3 molCH4.kgDQO-1; o que representa um aumento de produtividade de cerca de 9% e 30% quando comparado com a digestão anaeróbia de soro e glicerina puros, respectivamente. A produção de metano no melhor ensaio aconteceu predominantemente pela rota hidrogenotrófica. Para a produção de biohidrogênio, a maior produtividade e rendimento do reator foram obtidas no ensaio operado com razão de mistura de 75% soro e 25% glicerina, com 7 gDQO.L-1 de concentração afluente, tempo de ciclo de 3 h e tempo de enchimento de 1,5 h (modo batelada alimentada - COAV de 23,9 kgDQO.m-3.d-1), a 30°C: foi obtida uma produtividade molar de 129,0 molH2.m-3.d-1 e rendimento de 5,4 molH2.kgDQO-1. Esses resultados representam um aumento de produtividade de 145% em relação a mono-digestão do soro na condição inicial, o que indica o benefício significativo da adição de glicerina ao afluente, provavelmente devido à sua capacidade tamponante, e a otimização das condições operacionais. A adição de glicerina e o aumento da COAV balancearam as rotas de produção de hidrogênio, sendo produzido de forma mais equilibrada pelas vias do ácido acético, butírico e valérico. A caracterização do consórcio microbiano desse ensaio indicou que a comunidade microbiana presente no AnSBBR foi dominada por Ethanoligenens e Megasphaera. / The current research evaluated an anaerobic reactor, operated in batch or fed-batch mode, containing immobilized biomass in inert support and with recirculation of the liquid phase (AnSBBR), applied to the production of biohydrogen co-digesting glycerin (effluent from biodiesel production process) and whey (effluent from dairy industry). Stability, performance (regarding productivity and molar hydrogen yield) and conversion factor (between biogas produced and organic matter consumed) were analyzed according to the percentage of each substrate fed to the system, organic loading rate, filling time and temperature (20, 25, 30 and 35ºC). Assays were carried out using different substrates proportions and organic loading rates (10.3; 17.1 and 24.0 gCOD.L-1.d-1), which have been modified in function of: (i) influent concentration (3, 5 and 7 gCOD.L-1) and (ii) cycle length (4, 3 and 2 h, i.e. 6, 8 and 12 cycles daily). Assays were also carried out aiming for biomethane production using the proposed co-digestion (with AVOL of 7.6 gDQO.L-1.d-1) with different proportions of substrate mixture. For biomethane production, the assay conducted with 75% whey and 25% glycerin (COD basis) obtained the best results: molar productivity of 101.8 molCH4.m-3.d-1 and yield per applied load of 13.3 molCH4. kgCOD-1; which is an increase in productivity of about 9% and 30% when compared with the anaerobic mono-digestion of whey and glycerin, respectively. Methane production in this assay came mainly from the hydrogenotrophic route. For biohydrogen production, the highest productivity and yield were achieved in the assay operated with 75% whey and 25% glycerin, with 7 gCOD.L-1 of influent concentration, 3 h of cycle time and filling time of 1.5 h (fed batch mode - AVOL of 23.9 kgCOD.m-3.d-1), at 30°C: a molar productivity of 129.0 molH2.m-3.d-1 and yield of 5.4 molH2.kgCOD-1 were obtained. These results represent a productivity increase of 145% in relation to whey mono-digestion at its initial condition, which indicates the significant benefit of glycerin addition to the influent, probably due to its buffering capacity, and improvement of operational conditions. The addition of glycerin and the increase in AVOL balanced the hydrogen production routes, since hydrogen was produced similarly by the acetic, butyric and valeric acid routes. The characterization of the microbial consortium of this assay indicated that the microbial community present in the AnSBBR was dominated by Ethanoligenens and Megasphaera.

The organic wastes including olive oil mill residues are an inseparable part of food manufacturing processes while implying multi-faceted damages to the environment. A good quantity of research has been conducted to examine the biogas enhancement level in the anaerobic process of olive residues.  Seeking the optimum pretreatment method and the co-digesting substrates, the current study has conducted aggregative research on 155 experiments out of 22 studies. The conducted meta-analysis recognized the chemical type of pretreatments as the most effective treating procedures, according to which, application of the combined alkaline and lime, followed by trace metal cobalt supplementations are recognized as the most effective methods.  Furthermore, the study found intriguing results on the optimum type of olive main substrate, inoculum, digester type and effective volume as well as the superior country and year, in the anaerobic digestion of the olive mill residues.

Biogas production through anaerobic digestion is an important part towards the achievement of a bio-based and circular economy in Sweden. In fact, Swedish government proposed a strategy suggesting that biogas production should be increased from 2 TWh today to 7 TWh by 2030. Sweden has a large potential for biogas production from agricultural residues, not the least the Region Västra Götaland (RVG) where the stakeholders from the present study are located. The study explores the possibilities to use farm manure in co-digestion with deep bedding to produce biogas. The possibilities include two main alternatives for biogas production; mainly combined heat and power (CHP) to produce heat and electricity and biogas upgrading to produce bio-methane. The study took two existing organic farms in the municipality of Götene as a case study as well as an under-construction biogas plant by the company Gasum. The results of the present study also confirm that biogas could be a better option both economically and environmentally than fossil fuels. Additional results show that diesel consumption and energy prices are seen as hotspots that greatly influence both technical performance and economic profitability of biogas production. Another parameter is the geographical location of the studied system which could delimit or enhance the biogas production prospects depending on the proximity to gas grid or biogas unit. The aim of the study is to assess which of the studied alternatives is most profitable and has less environmental impacts; sending liquid manure to a biogas plant and receiving liquid fertilizer in exchange (centralized scenario) or invest in a biogas plant at the farm (on-farm scenario). A life cycle assessment (LCA) was conducted to compare environmental impacts of producing the equivalent of 1 MWh of biogas through on-farm plant and a biogas unit operated by the Finnish company Gasum. While a life cycle costing (LCC) was carried out considering a 10 year period with a 3% interest rate to analyze which of the two aforementioned options is more profitable for both farmers. Further this study aims to spur the interest of other scholars to further explore the potential of biogas/biomethane production within the agriculture sector and provide a better understanding of the different dynamics that impact the balance between energy provisions and the farm production process, and thus assist farmers to take part in the transition to a more renewable energy source.

This study aimed at seeking for the solution to recover the energy from agriculture waste in the Mekong Delta, Vietnam. The spent mushroom compost - a residue from the mushroom growing - was chosen for co-digestion with pig manure in anaerobic batch and semi-continuous experiments. The results showed that in case of spent mushroom compost made up 75% of the mixed substrate, the gained biogas volume was not significantly different compared to the treatment fed solely with 100% pig manure. The average produced biogas was 4.1 L×day-1 in the experimental conditions. The semi-continuous experiments remained in good operation up to the 90th day of the fermentation without any special agitating method application. The methane contents in both experiments were around 60%, which was significantly suitable for energy purposes. These results confirm that spent mushroom compost is possibly an acceptable material for energy recovery in the anaerobic fermentation process. / Nghiên cứu này nhằm tìm kiếm giải pháp thu hồi năng lượng từ chất thải nông nghiệp tại ĐBSCL, Việt Nam. Rơm sau ủ nấm - phế phẩm sau khi trồng nấm rơm - được chọn để ủ kết hợp với phân heo trong các bộ ủ yếm khí theo mẻ và bán liên tục. Kết quả cho thấy nếu phối trộn đến 75% rơm sau ủ nấm trong nguyên liệu ủ, tổng lượng khí thu được không khác biệt đáng kể so với thí nghiệm ủ 100% phân heo. Trong điều kiện thí nghiệm, lượng khí thu được trung bình là 4.1 L.ngày-1. Thí nghiệm ủ bán liên tục vẫn vận hành tốt ở ngày thứ 90 mặc dù mẻ ủ không được khuấy đảo. Hàm lượng khí mê-tan đo được chiếm khoảng 60% hoàn toàn có thể sử dụng cho các nhu cầu về năng lượng. Những kết quả thí nghiệm khẳng định có thể sử dụng rơm sau ủ nấm để thu hồi năng lượng thông qua quá trình ủ yếm khí kết hợp.

No description available.

CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / The production of renewable energy and fertilizer, through anaerobic biodegradation (AnBio) of waste from pig farming, presents itself as a strategic solution to minimize the negative effects associated with the large volume of manure generated in a small production space. However, further studies should be conducted to improve the understanding on the process and propose improvements. In this sense, this work was divided into three stages. In the first stage, a study was conducted to evaluate the changes that occur in organic matter and in organic and inorganic forms of nitrogen (N) and phosphorus (P) of the solid fraction of pig manure (PM) using anaerobic bench-top reactors as a function of seven hydraulic retention times (7, 14, 21, 28, 35, 42 and 49 days of biodegradation) and compared with the raw manure. In the second stage, we developed a study of anaerobic co-digestion, in a semi-continuous reactor, using the PM and the industrial waste of tomato processing (WTP) at different mixing ratios, to improve the performance of digestion and establish the best ratio of the two substrates for the production of biogas and methane. The following proportions were used (% PM + % WTP): 10% + 90%, 20% + 80%, 30% + 70%, 50% + 50% and 40% + 60%. In the third stage, there was an innovative study to recover the N present in the digestate generated after AnBio, using semipermeable membranes made of expanded polytetrafluoroethylene (PTFE) submerged in the material. This system consists of forcing the volatilization of N present in the digestate in the form of NH3 and then recover it in an acid solution of 1N H2SO4 flowing through the inside of the PTFE membrane. The N is recovered as the ammonium ion (NH4+), with potential for being used as fertilizer. Besides the digestate, raw pig manure (RPM) was used to compare the N recovery potential of both materials. The accumulation of the NH4+ formed was determined at nine sampling times (0, 7, 20, 30, 44, 54, 70, 79 and 93 hours). Based on the results obtained in the first stage, it was concluded that, during the digestion process, the organic matter of higher lability, represented by the carbon of the fulvic acid fraction and carbon oxidizable with 2.5 mL of H2SO4, was partially consumed, promoting the accumulation of recalcitrant organic matter at the end of the process. The contents of organic N and NH4+ reduced respectively by 45.2% and 54.2%, compared with their initial contents in the RPM, probably due to loss by volatilization. The P content reduced by 41.25% in relation to the initial content, due to the chemical precipitation of the inorganic fraction extractable in water with metallic cations within the reactor. In the case of co-digestion, increasing PM proportion to up to 30% of the feed mixture led to the maximum daily production of biogas (175 L) and the largest proportion of methane (60%). Amounts above 30% of manure in the mixture reduced biogas and methane production due to the increase of free NH3 concentration (272 mg L-1), which is toxic to most methanogens. As regards the recovery of N using PTFE membranes, it was observed that the recovery efficiency of the digestate was 12% higher compared with that observed in the RPM. Quantitatively, 4555 mg NH4+ could be recovered from the digestate in 93 hours of experiment, which can be used later as a source of N to agricultural crops. / A produÃÃo de energia renovÃvel e fertilizante, atravÃs da biodegradaÃÃo anaerÃbia (BioAn) dos dejetos da suinocultura, apresenta-se como uma soluÃÃo estratÃgica para minimizar os efeitos negativos associados ao grande volume de dejeto gerado em um reduzido espaÃo de produÃÃo. Contudo, mais estudos devem ser realizados para melhorar o entendimento do processo e propor melhorias. Nesse sentido, realizou-se este trabalho que foi dividido em trÃs etapas. Na primeira, foi realizado um estudo com o objetivo de avaliar as mudanÃas que ocorrem na matÃria orgÃnica e nas formas orgÃnicas e inorgÃnicas de nitrogÃnio (N) e fÃsforo (P) da fraÃÃo sÃlida do dejeto suÃno (DS), utilizando reatores anaerÃbios de bancada, em funÃÃo de sete tempos de retenÃÃo hidrÃulica (7, 14, 21, 28, 35, 42 e 49 dias de biodegradaÃÃo) e comparados com o dejeto nÃo degradado. Na segunda etapa, desenvolveu-se um estudo de co-digestÃo anaerÃbia, em um reator semicontÃnuo, utilizando o DS e o resÃduo da indÃstria do processamento do tomate (RPT) em diferentes proporÃÃes de mistura, visando melhorar o desempenho da biodegradaÃÃo e estabelecer a melhor proporÃÃo dos dois substratos para a produÃÃo de biogÃs e metano. Utilizaram-se as seguintes proporÃÃes (% de DS + % de RPT): 10% + 90%, 20% + 80%, 30% + 70%, 50% + 50% e 60% + 40%. Na terceira etapa, realizou-se um estudo inovador visando recuperar o N presente no digestato gerado apÃs a biodegradaÃÃo, utilizando membranas semipermeÃveis de politetrafluoroetileno expandido (PTFE) submersas no material. Esse sistema consistiu em forÃar a volatilizaÃÃo do N presente no digestato na forma de NH3 e, posteriormente, recuperÃ-lo em uma soluÃÃo Ãcida de H2SO4 1N que circulava pelo interior da membrana de PTFE. O N foi recuperado na forma do Ãon amÃnio (NH4+), com potencial para ser utilizado como fertilizante. Utilizou-se alÃm do digestato, DS nÃo degradado, para comparaÃÃo do potencial de recuperaÃÃo de N dos dois materiais. A determinaÃÃo do acÃmulo de NH4+ formado foi realizada em nove tempos de amostragem (0, 7, 20, 30, 44, 54, 70, 79 e 93 horas). Com base nos resultados obtidos na etapa 1, concluiu-se que durante a biodegradaÃÃo, a matÃria orgÃnica de maior labilidade, representada pelo carbono da fraÃÃo Ãcido fÃlvico e carbono oxidÃvel com 2,5 mL de H2SO4, foi parcialmente consumida, promovendo o acÃmulo de matÃria orgÃnica recalcitrante no final do processo. Os conteÃdos de N orgÃnico e NH4+ reduziram respectivamente, 45,2% e 54,2% em relaÃÃo aos seus conteÃdos iniciais no dejeto nÃo degradado, devido, provavelmente, a perda por volatilizaÃÃo. O conteÃdo de P reduziu 41,25% em relaÃÃo ao seu conteÃdo inicial, devido à precipitaÃÃo quÃmica da fraÃÃo inorgÃnica extraÃvel em Ãgua com cÃtions metÃlicos no interior do reator. No caso da co-digestÃo, o aumento da proporÃÃo do DS atà o limite de 30% da mistura de alimentaÃÃo, proporcionou a mÃxima produÃÃo diÃria de biogÃs (175 L) e a maior proporÃÃo de metano (60%). Quantidades superiores a 30% de dejeto na mistura, reduziram a produÃÃo de biogÃs e metano devido ao aumento da concentraÃÃo de NH3 Livre (272 mg L-1) tÃxico a maioria dos microrganismos metanogÃnicos. No que se refere à recuperaÃÃo do N utilizando as membranas de PTFE, observou-se que a eficiÃncia de recuperaÃÃo no digestato foi superior em 12% em relaÃÃo ao observado no dejeto nÃo degradado. Em termos quantitativos, conseguiu-se recuperar 4555 mg de NH4+ proveniente do digestato durante 93 horas de experimento que poderÃ, posteriormente, ser utilizado como fonte de N para as culturas agrÃcolas.

Algae that are grown in wastewater treatment lagoons could be an important substrate for biofuel production; however, the low C/N ratio of algae is not conducive to anaerobic digestion of algae with economically attractive methane production rates. Increasing the C/N ratio in anaerobic, laboratory scale, batch reactors by blending algal biomass with sodium acetate resulted i increased methane production rates as the C/N ratio increased. The highest amount of methane was produced when the C/N was 21/1. When the C/N was 24/1, the biogas production rate decreased. Batch experiments were done to evaluate the effect of optimizing the C/N ratio on methane production from algae and to identify the most essential information needed to conduct research on co-digestion of algal biomass using the continuous, high-rate, up-flow anaerobic sludge blanket (UASB) reactor system. Based on the results obtained from batch reactor experiments, anaerobic co-digestion of algal biomass, obtained by continuous centrifugation from the Logan City, Utah, 5th stage wastewater treatment lagoon, and sodium acetate was conducted using laboratory scale UASB reactors with the C/N ratio in the feedstock adjusted to 21/1. Duplicate, 34 L UASB reactor systems were built of poly(methyl methacrylate). Both reactors were seeded with 11 L of anaerobic sediment from the 3rd stage lagoon. The pH of the feedstock was adjusted to the neutral range. The feedstock was initially introduced at a low organic loading rate of 0.9 g/L.d with a hydraulic retention time (HRT) of 7.2 days and then increased up to 5.4 g/L.d and a HRT of 5.5 days. These organic loading rates corresponded to an initial influent chemical oxygen demand (COD) of 6.25 g/L and increased to 27.2 g/L. Methane production increased from 270 mL/g to 349 mL/g COD biodegraded. COD removal efficiency was 80% and biogas methane composition was 90% at steady state. Algal biomass contributed 33-50% of the COD in the feed stock depending on the COD of the algae paste from centrifugation. The shortest HRT at which steady state was not affected was 5.5 days. At lower HRT all monitored parameters showed a slight decrease after the 75th day of operation.

<p dir="ltr">Improving environmental sustainability in energy production and waste management are of critical importance. Anaerobic digestion (AD) uses microbes to biologically decompose organic waste and produce biogas, which can be used for various forms of sustainable energy. It can be particularly valuable for livestock facilities considering AD of their manure, and potentially other feedstocks as well, a process known as co-digestion. Improved understanding of co-digestion of agro-industrial feedstocks is critical for these facilities. Understanding the macromolecular composition (carbohydrate, protein, and lipid portions) of potential AD feedstocks has the potential to provide important information for predicting important parameters of AD behavior. However, the stability of these macromolecules in AD samples during long-term storage must be confirmed. Furthermore, synergistic and antagonistic impacts of co-digestion on methane production and digestate composition need to be more thoroughly explored.</p><p dir="ltr">This dissertation investigates the impact of storage at refrigeration temperatures (4°C) for up to one-year on the macromolecular composition of various agro-industrial feedstocks (beef manure, starch, slaughterhouse waste, soap stock, and filter press slurry) and anaerobic co-digestion samples. These same feedstocks were co-digested with manure in batch digesters at different proportions, using two or three feedstocks to determine possible synergistic effects.</p><p dir="ltr">The findings show that minimal macromolecular degradation occurred in AD samples during storage at refrigeration temperatures for up to one-year. A major exception was samples containing high concentrations of readily biodegradable starches, which did experience >50% carbohydrate degradation. This indicates a need for methodological rigor during sample storage and reporting experimental design.</p><p dir="ltr">Furthermore, the co-digestion experiments demonstrated frequent improvements or synergy in specific methane yield, methane production rate, and a wide variety of physical and chemical parameters in the digester effluent. Specific methane yield was shown to be at least additive, with improvement ranging from 3-168%. Some improvements in kinetic performance were also observed and quantified. Statistical results suggest that influent characteristics could be useful as predictors for methane production. This research could catalyze additional work needed to optimize co-digestion feeding strategies for full-scale digesters.</p>