The biochemical methane potential (BMP) of a substance is a measure of the volume of methane gas produced per unit mass of that substance, through the process of anaerobic biodegradation. As the socio-economic consequences of climate change have become more apparent, the ability to predict the long-term cumulative environmental impact of various human activities has become more necessary. Landfills can be a substantial source of methane (a greenhouse gas) to the atmosphere, and consequently BMP is an important tool for predicting the potential cumulative long-term impacts of a landfill to the environment. From a strictly economic perspective, the practice of landfill methane extraction for industrial uses is becoming much more common. In this case, BMP is an important tool for predicting the economic feasibility of such a project. Current methods for determining the BMP of municipal solid wastes (MSW) are both time-consuming and inconsistent. A review of literature on the topic yields many different descriptions of the test, with large variations in sample sizes, incubation times, procedures, etc. Most of these methods also require expensive, and specialized equipment. This thesis describes a simple approach to the BMP test that might be carried out in a variety of laboratory settings, such as an on-site lab equipped with basic, simple, and inexpensive equipment. The method relies on a much larger than typical sample mass to produce large volumes of gas that are measured for composition multiple times over the course of the test. The volume and composition data is then used to produce a cumulative methane potential curve which can be fitted to a first-order decay model in order to predict an ultimate BMP value. The taking of multiple measurements on large volumes of gas, allows for the use of a portable field instrument called the GEMTM2000 to measure gas composition. By fitting the data to a curve in order to determine ultimate methane potential, individual measurement errors are averaged out and the final result has a precision similar to more traditional BMP methods, which rely on bulky and expensive gas chromatographs. Testing has been conducted on MSW samples from 3 separate sites. The method used involved comparatively large samples of waste (~200 g) and no limit was set on incubation time. The use of large waste samples produces large quantities of gas that must be collected and analyzed often. The method provided favourable results, consistent within acceptable limits of variability when compared with other BMP methods. There is even some evidence suggesting that the use of large waste samples improves the accuracy of the test, despite the use of equipment which provides less precise measurements of gas concentration. Given the long duration required for testing, the results were also evaluated for possible correlations between loss on ignition data and specific gravity measurements; two simple tests that can be conducted rapidly. Both data sets show a rough correlation with BMP, and may be used to quickly estimate ultimate BMP values, but the loss on ignition relationship provides the better correlation. Lastly, initial steps were taken in the development of what has been dubbed the Biochemical CO2 Potential (BCP) test, taking advantage of the relatively quicker rate of aerobic degradation. There are preliminary indications that the BCP method may be a viable alternative to the BMP, but the data set so far is small and further research is required to confirm that hypothesis.

abstract: Eighty-two percent of the United States population reside in urban areas. The centralized treatment of the municipal wastewater produced by this population is a huge energy expenditure, up to three percent of the entire energy budget of the country. A portion of this energy is able to be recovered through the process of anaerobic sludge digestion. Typically, this technology converts the solids separated and generated during the wastewater treatment process into methane, a combustible gas that may be burned to generate electricity. Designing and optimizing anaerobic digestion systems requires the measurement of degradation rates for waste-specific kinetic parameters. In this work, I discuss the ways these kinetic parameters are typically measured. I recommend and demonstrate improvements to these commonly used measuring techniques. I provide experimental results of batch kinetic experiments exploring the effect of sludge pretreatment, a process designed to facilitate rapid breakdown of recalcitrant solids, on energy recovery rates. I explore the use of microbial electrochemical cells, an alternative energy recovery technology able to produce electricity directly from sludge digestion, as precise reporters of degradation kinetics. Finally, I examine a fundamental kinetic limitation of microbial electrochemical cells, acidification of the anode respiring biofilm, to improve their performance as kinetic sensors or energy recovery technologies. / Dissertation/Thesis / Doctoral Dissertation Civil, Environmental and Sustainable Engineering 2020

The objective of this paper is to evaluate the effectiveness of leachate recirculation and bioreactor landfills at enhancing biodegradation, and to optimize the operation of a bioreactor. Waste Management has been examining leachate recirculation landfills for several years. Samples of Municipal Solid Waste (MSW) from existing leachate recirculation (LR) landfills were collected and analyzed for several physical and biochemical properties. These parameters of interest were moisture content, pH, density, temperature, volatile solids, cellulose/lignin ratios, and biological methane potential (BMP). Leachate recirculation increased the dry density 55% faster and decreased the BMP 125% more rapidly. Moisture content was the biggest factor influencing overall degradation. Therefore, leachate reciculation effectively increases biodegradation of MSW in landfills. Waste Management built a pilot-scale bioreactor in Franklin, WI, which was sampled for one year. It contained a bioreactor side and a control side. The volatile solids, cellulose, and BMP degradation rates for the bioreactor were increased by 56%, 87%, and 271% versus the control, respectively. Moisture content was the biggest factor influencing overall degradation. The column study is designed to optimize three parameters under the control of an operator: moisture content, initial aeration period, and biosolids addition. The optimum moisture content is above 45%, but it is not safe to operate heavy equipment on refuse with greater than 45% moisture. Initial aeration did not speed up the overall degradation, but it did shorten the acidogenic phase. Finally, biosolids did not have a significant effect on degradation rates. The columns maintained an average temperature of 70oF. / Master of Science

Currently Vietnam is facing several problems with waste handling. For instance, a lot of the municipal organic solid waste is dumped at landfills, which contributes to environmental difficulties such as greenhouse gas emissions. Anaerobic digestion has proven to be an adequate method for solving environmental problems such as waste treatment, where biogas can be produced. The methane content in the biogas can subsequently be used as a prosperous energy source for heating, electricity and vehicle fuel. The production and utilization of biogas in Vietnam is in a developing face. However, there are issues that should be tackled to improve and expand the biogas production and use. In Vietnam the main substrate used for anaerobic digestion is animal manure as most of the biogas digesters are placed on farms. The purpose of this master thesis was to identify additional potential substrates for biogas production, with focus on Thái Nguyên city and Sông Công city in the Thái Nguyên province. In order to find suitable substrates, interviews and literature research were carried out in Vietnam. Subsequently biochemical methane potential (BMP) tests were performed for the identified and acquired substrates. The BMP-tests were first performed at Thái Nguyên University but as the results were inconclusive, further experiments were performed at Linköping University (Sweden) where eight substrates from the Thái Nguyên province were investigated. The identified substrates used for the BMP-tests were three types of beer waste from the Vicoba brewery in Thái Nguyên city, food waste from different restaurants in Sông Công city, fruit waste from the fruit market in Thái Nguyên and household vegetable waste. The highest methane yield could be observed for household vegetable waste (543 Nml/g VS) followed by beer waste (yeast) with a methane potential of 497 Nml/g VS. Beer waste (hops boiling) had the lowest methane potential with a value of 230 Nml/g VS. Estimation of the total methane potential in both cities together from food waste from restaurants, beer waste and sewage sludge from the upcoming waste water treatment plant (WWTP) in Thái Nguyen city were made by combining data from interviews, literature values and the BMP-results. The estimation showed that from Thái Nguyên City and Sông Công city about 137,500 m3 CH4/year can be produced from food waste from restaurants, about 1.7 millionCH4 m3/year can be produced from sludge from the WWTP in Thái Nguyên city (under construction) and there is also a possibility to produce about 10,700 m3 CH4/year from the beer brewery in Thái Nguyên city. Thus, the total estimated methane potential sums up to 1.8 million m3 CH4/year. The results show that Thái Nguyên city and Sông Công city have potential wastes that preferably could be used as substrates for biogas production which could add on to the biogas produced currently at farm level in the Thái Nguyên region. / I dagsläget står Vietnam inför svåra problem med rådande avfallshantering. En stor del av det organiska avfallet deponeras. Detta bidrar till miljöproblem som exempelvis utsläpp av växthusgaser. Kontrollerad rötning har visat sig vara en bra metod för avfallshantering av organiskt avfall, eftersom biogasen som produceras exempelvis kan användas som energikälla för matlagning, elektricitet och fordonsbränsle, samtidigt som avfallsmängden kraftigt reduceras. Utvecklingen av kommersiell biogasproduktion i Vietnam är fortfarande i ett inledande stadie. De främsta substraten för biogassubstratet som används i landet i nuläget är olika typer av gödsel med anledning av att de flesta rötkammare är placerade på bondgårdar. Syftet med denna studie är att undersöka kompletterande potentiella substrat som kan användas för biogasproduktion i städerna Thái Nguyên och Sông Công som är belägna i provinsen Thái Nguyên. För att identifiera möjliga biogassubstrat genomfördes intervjuer på plats tillsammans med litteraturundersökningar. Vidare genomfördes metanpotentialbestämningar (BMP) för identifierade, utvalda och, erhållna substrat. Det visade sig ej vara möjligt inom tidsramen för besöket att genomföra BMP-testerna på ett fullgott sätt vid Thái Nguyêns universitet med anledning av begränsningar i metodförutsättningar, varför BMP-tester även genomfördes på Linköpings universitet. Totalt testades metanpotentialen för åtta olika substrat från städerna Thái Nguyên och Sông Công. De identifierade substraten som användes i BMP-studien var tre typer av bryggeriavfall från Vicoba bryggeri i Thái Nguyên, matavfall från olika restauranger i Sông Công, fruktavfall från fruktmarknaden i Thái Nguyên och hushållsavfall från ett hushåll i Thái Nguyên. Det högsta metanutbytet kunde observeras för matavfall från hushåll (543 Nml/g VS) följt av bryggeriavfall i form av jäst (497 Nml/g VS). Ölavfall från vörtkokning påvisade det lägsta metanutbytet av samtliga testade substrat motsvarande 230 Nml/g VS. En uppskattning av den totala metanpotentialen i de båda städerna från matavfall från restauranger, bryggeriavfall samt avloppsslam från reningsverket som är under uppbyggnad i Thái Nguyên genomfördes baserat på intervjuer, litteraturvärden samt genomförda metanpotentialtester (BMP). Uppskattningen visade att cirka 137 500 m3 CH4/år skulle kunna produceras från matavfall från restauranger, cirka 1,7 miljoner CH4 m3/år från avloppsreningsverksslam samt från ölbryggeriet i Thái Nguyên är det möjligt att producera cirka 10 700 CH4 m3/år. Sammantaget indikerar det en uppskattad metanpotential motsvarande ca 1,8 miljoner CH4 m3/år. Slutsatsen av den här studien visar att det finns stor potential för biogasproduktion i Thái Nguyên och Sông Công. / Developing strategies and methods for participatory planning in Thái Nguyên and Linköping

Submitted by Edineia Teixeira (edineia.teixeira@unioeste.br) on 2017-08-30T13:20:01Z No. of bitstreams: 2 Deisi_Tapparo2017.pdf: 1334800 bytes, checksum: e1f7fae75650df8c87e6f134d2dad8cf (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-08-30T13:20:01Z (GMT). No. of bitstreams: 2 Deisi_Tapparo2017.pdf: 1334800 bytes, checksum: e1f7fae75650df8c87e6f134d2dad8cf (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-02-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The swine breeding stands out on worldwide due to its constant growth. However, environmental problems have increased as the activity gains recognition, consequently, planning and management of waste produced have been required in the systems. Animal carcasses disposal inside or outside the animal rearing farms is under concern and object of discussion about good practices to do it considering biosecurity aspects. One alternative is the swine manure and swine carcass co-digestion in order to improve biogas production. At the same time, it is known that animal carcass has some pathogenic microorganisms of zoonotic importance. In this context, this research aimed at studying swine carcass co-digestion and swine manure as well as its implications on biogas yield and digestate sanitation. This study was carried out under mesophilic temperature (37 ºC) and triplicate tests. Biogas volume was measured using eudiometer tubes, according to VDI 4630. The trials used the carcass sample digestion in a separate way and loading rates of carcass/manure were 3, 7.5 and 15kg.m-3manure, which represented 1, 2.5 and 5 times of mortality/manure production rates on typical swine farms (Mortality rate of 7% .year-1 for matrices). The inactivation trials were carried out in separated. Then it was evaluated the inactivation of the following microorganisms models (E. coli, Salmonella enterica serovar Senftenberg, PCV2, and bacteriophage MS2 and PhiX-174). Four inactivation strategies were carried out at two temperatures (24 ºC and 37 ºC) and two swine carcass/swine manure ratios were also studied (3kgcarcass.m-3manure and 15 kgcarcass.m-3manure). The swine carcass presented biochemical methane potential (BMP) of 1076 ± 48 LNbiogas.kgSVadic-1, and its co-digestion with swine manure increases biogas production potential when compared to manure monodigestion. The model microorganisms such as E. coli, S. Senftenberg and PCV2 (37°C) were completely inactivated until 30 days, while PCV2 (24°C), MS2 and PhiX-174 were more resistant. The temperature of co-digestion process influences the time required for microorganisms’ inactivation. Inactivation results suggest that, during co-digestion at 37°C, there is a greater pathogen reduction when compared to the same process at 24° C. It is recommended to use a pre-treatment process to biodigestor without heating system and under mesophilic temperature to ensure biosafety. / A suinocultura se destaca no cenário mundial devido ao seu constante crescimento. Todavia, os problemas ambientais aumentam à medida que a atividade ganha reconhecimento, por isso, são necessários planejamento e gestão dos resíduos produzidos nos sistemas. Um dos desafios da atividade é a destinação de animais mortos, logo, são necessárias alternativas que aliem proteção do meio ambiente e saúde pública bem como opções de baixo custo. Uma das alternativas é realizar a codigestão de carcaça suína com dejeto suíno para melhorar a produção de biogás. Ao mesmo tempo, é de conhecimento que a carcaça animal possui micro-organismos patogênicos de importância zoonótica. Nesse contexto, o objetivo desta pesquisa foi estudar a codigestão de dejeto suíno e carcaça suína, suas implicações sobre a produção de biogás e sanitização do digestato. Os estudos de digestão foram conduzidos em batelada, sob condições mesofílicas (37ºC) e em triplicata. Foram utilizados tubos eudiômetros para mensurar o biogás produzido, conforme norma VDI 4630. Os experimentos envolveram a digestão de amostras de carcaça em separado e das relações de mistura entre carcaça e dejeto nas seguintes proporções: 3; 7,5 e 15 kgcarcaça.m-3dejeto, as quais representaram 1; 2,5 e 5 vezes a mortalidade encontrada em granjas comerciais (mortalidade de 7%.ano-1 para matrizes). Os experimentos de inativação de patógenos foram conduzidos em separado. Avaliou-se a inativação de micro-organismos modelos (E. coli, Salmonella entérica serovar Senftenberg, PCV2, MS2 e PhiX-174). Quatro estratégias de inativação foram estudadas: duas temperaturas (24ºC e 37ºC) e duas relações de carcaça suína/dejeto suíno (3kg.m-3 e 15kg.m-3). Os resultados mostraram que a carcaça suína tem um potencial de 1076 ± 48 LNbiogás.kgSVadic-1, e a sua codigestão com dejeto suíno aumenta o potencial de produção de biogás comparando com a monodigestão do dejeto. Os micro-organismos modelo E. coli, S. Senftenberg e PCV2 (37 ºC) foram totalmente inativados em 30 dias, enquanto o PCV2 (24 ºC), MS2 e PhiX -174 foram mais resistentes. A temperatura do processo de codigestão influencia no tempo necessário para a inativação dos micro-organismos. Os resultados de inativação sugerem que, durante a codigestão a 37 ºC, ocorre maior redução de patógenos quando comparada ao mesmo processo a 24 ºC. Recomenda-se a utilização de processo de pré-tratamento para biodigestores sem sistema de aquecimento e em temperaturas mesofílicas, a fim de garantir a biossegurança.

In this study, anaerobic treatability of opium alkaloid wastewater and the effect of radiation pretreatment (gamma-rays) on anaerobic treatability were investigated. Biochemical Methane Potential (BMP) assay was performed with alkaloid wastewater having initial COD values of 2400, 6000 and 9600 mg/L with and without basal medium (BM). The highest anaerobic treatment efficiency of 77% was obtained in the BMP reactor containing alkaloid wastewater with initial COD of 9600 mg/L and BM. Co-substrate use was investigated by using BMP assay. Alkaloid wastewater having initial COD concentrations of 9000, 13000 and 18000 mg/L were used with glucose, acetate and glucose-acetate as co-substrates. Results revealed that co-substrate use did not improve alkaloid removal efficiency significantly but it abrogated the acclimation period of anaerobic bacteria to alkaloid wastewater. Continuous reactor experiments were carried out in Upflow Anaerobic Sludge Blanket (UASB) reactors. Highest overall efficiencies (above 80%) were obtained in the reactor fed with co-substrate (R2) for all initial COD concentrations. Up to 78% removal efficiency was obtained in R1 (fed with alkaloid wastewater only) at initial COD concentration of 19 g/L. Effect of radiation was sought by using BMP assay with two initial COD concentrations of 14 and 25 g/L, and two radiation doses 40 and 140 kGy. At 14 g/L COD, there was no effect of radiation on gas production for both doses. However at initial COD of 25 g/L, reactors containing wastewater dosed with 140 and 40 kGy produced gas with higher rates above certain point with respect to raw wastewater.

Il mais rappresenta una delle colture più diffuse nel Nord Italia. Negli ultimi anni si è assistito ad un notevole incremento della superficie a mais legato soprattutto all'uso dell'insilato di mais come substrato per la produzione di biogas. Per questo motivo è necessario avere il maggior numero di informazioni possibili per migliorare le performance della coltura. In letteratura ci sono molti studi che valutano l’impatto dell’ambiente e del management sulle caratteristiche chimico nutrizionali e sul potenziale metanigeno del foraggio di mais ma non ci sono lavori che considerano entrambi i parametri. L’obiettivo della tesi è stato quello di investigare come il danno da grandine , la genetica e il momento di raccolta possano influenzare la composizione della pianta intera tradotta come potenziale metanigeno e valore nutrizionale del foraggio. / In the Po Valley the maize crop represent one of the most cultivated plant used for cattle feeding but in the last 10 years it is also used as biogas substrate. Considering the importance of this cultivation, there is the continuous need to obtain information about this plant with the aim to improve the crop performance. There are numerous studies investigating the impact of environmental aspects and management practices on chemical and nutritional composition, and methane production in the literature but very few that evaluate those parameters together. The general objective of this thesis is to investigate how hail damage, type of hybrid and the harvesting date affect the whole plant composition. To accomplish this, two specific objectives are posed: i) verify the effects of hail damage levels on yield, chemical and nutritional feature as well as on BMP of maize grown in the Po Valley; and ii) to evaluate the value of different hybrids for animal nutrition and methane production in anaerobic fermenters and as delaying harvesting after the usual stage of maturity affects these features. It was also aimed to verify if chemical composition and in vitro digestibility tests could allow to estimate methane yield potential in maize whole plant.

Orientador: Marcus César Avezum Alves de Castro / Resumo: No Brasil são geradas quantidades significativas de resíduos orgânicos provenientes das perdas no segmento de produção e processamento da cadeia de fornecimento de alimentos, ou desperdiçadas no varejo e no consumo final. Ainda, no país há carência de aplicações do processo de digestão anaeróbia no tratamento dos resíduos orgânicos alimentares, tornando pertinente seu estudo. Este trabalho analisou a influência de diferentes proporções de resíduos alimentares no processo de biometanização. Os substratos consistiram de resíduos orgânicos coletados em restaurante universitário, sendo divididos em dois grupos: Resíduos de Pré-Preparo dos alimentos (RPP) e Resíduos de Sobras das refeições (RS). Testes em batelada foram realizados para avaliar o Potencial Bioquímico de Metano (BMP) das diferentes proporções de resíduos, sob condições mesofílica e termofílica, tendo como fontes de inóculos dois lodos anaeróbios granulares provenientes de reatores UASB (Upflow Anaerobic Sludge Blanket). Para verificar a atividade dos lodos foram realizados testes de Atividade Metanogênica Específica (AME), tendo o acetato como fonte de carbono, com aplicação de diferentes relações Substrato/Inóculo (So/Xo) (0,5, 1,0 e 1,5). Os resultados dos testes de AME sob condições mesofílica e termofílica demonstraram bom desempenho dos inóculos com índices 0,1965 e 0,1559 g DQOCH4.g STV-1.d-1, respectivamente, sendo que a relação So/Xo=1,0 foi a mais indicada para aplicação na biodigestão anaeróbia dos resíduo... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In Brazil, significant amounts of organic waste are generated from losses in the production and processing segment of the food supply chain, or wasted on retail and final consumption. Still, in the country there is a lack of applications of the anaerobic digestion process in the treatment of organic food residues, making its study pertinent. This work analyzed the influence of different proportions of food residues on the biomethanization process. The substrates consisted of organic residues collected in a university restaurant, being divided into two groups: Food Pre-Preparation Residues (RPP) and Residues of Leftovers from meals (RS). Batch tests were carried out to evaluate the Biochemical Potential of Methane (BMP) of the different proportions of residues, under mesophilic and thermophilic conditions, having as inoculum sources two granular anaerobic sludge from UASB (Upflow Anaerobic Sludge Blanket) reactors. In order to verify the activity of the sludges, tests of Specific Methanogenic Activity (AME) were carried out, with acetate as carbon source, applying different Substrate/Inoculum (So/Xo) ratios (0.5, 1.0 and 1.5). The results of the AME tests under mesophilic and thermophilic temperatures showed good performance of the inoculum with indexes 0.1965 and 0.1559 g DQOCH4.g STV-1.d-1, respectively, with the ratio So/Xo=1.0 was the most indicated for application in anaerobic biodigestion of food waste. BMP tests under different proportions of food residues demonstrated ... (Complete abstract click electronic access below) / Mestre

Submitted by Neusa Fagundes (neusa.fagundes@unioeste.br) on 2017-09-05T19:08:26Z No. of bitstreams: 1 Thiago_Edwiges2017.pdf: 2041114 bytes, checksum: f435c702dd49431aa0534c4ce49e2533 (MD5) / Made available in DSpace on 2017-09-05T19:08:26Z (GMT). No. of bitstreams: 1 Thiago_Edwiges2017.pdf: 2041114 bytes, checksum: f435c702dd49431aa0534c4ce49e2533 (MD5) Previous issue date: 2017-08-18 / The economical development and urbanization process have contributed to the increase in solid waste generation and problems related to final disposal. Thus, the National Solid Waste Policy reinforces treatment in order to improve efficiency in the management of solid waste as one of its priorities and stimulates to recover and use energy. Anaerobic digestion has been suggested as a promising approach to the treatment of organic fraction of solid waste, mainly because it represents an opportunity to reduce environmental pollution and minimizes impacts concerning the energy crisis. So, this trial aimed at evaluating FVW biogas potential, collected in a wholesale market (Unit from Foz do Iguaçu/PR) through batch and semicontinuous tests. Fruits and vegetables trading from that unit generates approximately 70,500 t year-1, with 2,800 kg d-1 solid waste, composed of almost 85% organic matter. The influence of chemical composition of twelve FVW different samples with different compositions on biochemical methane potential (BMP) was analyzed. The BMP ranged from 288 LN CH4 kg VS-1 to 516 LN CH4 kg VS-1, with significant statistical differences among means. This was explained by in the waste chemical composition over time. BMP variation was most strongly correlated for lipid content and high calorific values (HCV). Linear regression analyses were carried out to develop statistical models to predict as fast as possible methane potential of this kind of waste. The models were analyzed according to chemical compounds and HCV based on simple and multiple regression. The model with the best statistical metrics included lipid, protein, cellulose, lignin, and HCV, with a 92.5% R² and lignin content negatively correlated to BMP. Since HCV and lipids were strongly correlated, and because HCV can be determined more rapidly than chemical composition, HCV may be useful for predicting BMP. In addition to batch tests, the performance of anaerobic digestion was also investigated in a semicontinuous mode using a FVW mixture as a single substrate. The performance of a continuous stirred tank reactor (CSTR) was monitored along with the gradual increase of organic loading rates (OLR) from 0.5 gVS L–1 d–1 to 5.0gVSL–1d–1. BMP of FVW used as a feedstock to CSTR was 370 LN CH4 kg VS-1 with 81% biodegradability. During the whole trial pH was stable and there was an adequate level of buffering capacity in the system. Volumetric biogas production (LN biogas L–1 d–1) increased linearly (R² = 94.4%) according to OLR increase. On the other hand, the specific methane production (LN CH4 kg VS-1) has registered the best performance at an OLR of 3.0 g VS L–1 d–1 and 30 days of hydraulic retention time, with 285 LN CH4 kg VS-1 added, reaching 74% of BMP measured by batch tests. A clear accumulation of volatile fatty acids (VFA) was monitored with a decreased specific methane yield was detected with an OLR above 3.0 g VS L–1 d–1. / O crescimento econômico e o processo de urbanização vêm contribuindo para o aumento da geração de resíduos sólidos e problemas relacionados à disposição final. A Política Nacional de Resíduos Sólidos reforça o tratamento com o intuito de melhorar a eficiência quanto ao gerenciamento dos resíduos sólidos no país, como uma de suas prioridades e enfatiza o incentivo à recuperação e ao aproveitamento energético. A biodigestão anaeróbia tem sido apontada como uma abordagem promissora ao tratamento da fração orgânica dos resíduos sólidos, sobretudo por representar oportunidade de reduzir a poluição ambiental e minimizar os impactos da crise energética. Assim, o objetivo deste trabalho foi avaliar o potencial de produção de biogás de resíduos de frutas e hortaliças (RFH) coletados na Central de Abastecimento (CEASA – Unidade de Foz do Iguaçu/PR) a partir de testes em batelada e em regime semicontínuo. A comercialização de frutas e hortaliças da unidade é de aproximadamente 70.500 t ano-1, com geração de resíduos sólidos de 2.800 kg d-1, compostos por aproximadamente 85% de matéria orgânica. A influência da composição química de doze amostras de RFH com diferentes composições sobre o potencial bioquímico de metano (PBM) foi analisada. O PBM dos resíduos variou entre 288 LN CH4 kg SV-1 e 516 LN CH4 kg SV-1, com diferenças estatísticas significativas entre as médias, o que pôde ser explicado pela variação na composição química dos resíduos ao longo do tempo. A variação do PBM foi mais fortemente correlacionada à variação do teor de lipídeos e do poder calorífico superior (PCS). Foram realizadas análises de regressão linear visando desenvolver modelos estatísticos para estimar, de forma mais rápida, o potencial metanogênico deste tipo de resíduo. Os modelos foram analisados considerando os componentes químicos e o PCS a partir de regressão linear simples e múltipla. O modelo com as melhores métricas estatísticas foi obtido considerando lipídio, proteína, celulose, lignina e PCS, com R² de 92,5% e com teor de lignina negativamente correlacionado ao PBM. Como o PCS e os lipídeos apresentaram forte correlação, e como o PCS pode ser determinado, em geral, de forma mais rápida que a composição química, o PCS pode ser considerado um parâmetro útil para a estimava do PBM. Além dos testes em batelada, investigou-se também o desempenho da biodigestão anaeróbia em regime semicontínuo utilizando-se uma mistura de RFH como único substrato. O desempenho de reator de mistura completa (do inglês CSTR) foi monitorado juntamente com o aumento gradativo da carga orgânica volumétrica (COV) de 0,5 g SV L-1 d-1 até 5,0g SV L-1 d-1. O PBM dos RFH utilizado para alimentar o reator foi 370 LN CH4 kg SV-1 com biodegradabilidade de 81%. Durante todo o ensaio o pH se manteve estável e o sistema apresentou boa capacidade tampão. A produção volumétrica de biogás (LN biogás L-1 d-1) aumentou de forma linear (R² = 94,4%) de acordo com aumento da COV. Já a produção específica de metano (LN CH4 kg SV-1) indicou o melhor desempenho com COV de 3,0 g SV L-1 d-1 e 30 dias de tempo de retenção hidráulica, com 285 LN CH4 kg SV-1 adicionados, e atingiu 74% de PBM, medido a partir dos testes em batelada. Observou-se um acúmulo evidente de ácidos graxos voláteis (AGV), com consequente redução da produção de metano a partir da COV acima de 3,0 g SV L-1 d-1.

<p>Anaerobic digestion uses a mixed, microbial community to convert organic wastes to biogas, thereby generating a clean renewable energy and reducing greenhouse gas emissions. However, few studies have quantified the relationship between waste composition and the subsequent physical and chemical changes in the digester. This Ph.D. dissertation aimed to gain new knowledge about how these differences in waste composition ultimately affect digester function. This dissertation examined three areas of digester function: (1) hydrogen sulfide production, (2) digester foaming, and (3) methane yield. </p> <p>To accomplish these aims, a variety of materials from four different large-scale field digesters were collected at different time points and from different locations within the digester systems, including influent, liquid in the middle of the digesters, effluent, and effluent after solids separation. The materials were used for biochemical methane potential (BMP) tests in 43 lab-scale lab-digester groups, each containing triplicate or duplicate digesters. The materials from field digesters and the effluents from the lab-digesters were analyzed for an extensive set of chemical and physical characteristics. The three areas of digester function were examined with the physical and chemical characteristics of the digester materials and effluents, and the BMP performances. </p> <p>Hydrogen sulfide productions in the lab-digesters ranged from non-detectable to 1.29 mL g VS^-1. Higher H₂S concentrations in the biogas were observed within the first ten days of testing. The initial Fe(II) : S ratio and OP concentrations had important influences on H₂S productions. Important parameters of digester influents related to digester foaming were the ratios of Fe(II) : S, Fe(II) : TP, and TVFA : TALK; and the concentrations of Cu. Digesters receiving mixed waste streams could be more vulnerable to foaming. The characteristics of each waste type varied significantly based on substrate and inoculum type, and digester functioning. The influent chemical characteristics of the waste significantly impacted all aspects of digester function. Using multivariate statistics and machine learning, models were developed and the prediction of digester outcomes were simulated based on the initial characteristics of the waste types. </p>