abstract: Seeking to address sustainability issues associated with food waste (FW), and fat, oil, and grease (FOG) waste disposal, the City of Mesa commissioned the Biodesign Swette Center for Environmental Biotechnology (BSCEB) at Arizona State University (ASU) to study to the impact of implementing FW/FOG co-digestion at the wastewater treatment plant (WWTP). A key issue for the study was the “souring” of the anaerobic digesters (ADs), which means that the microorganism responsible for organic degradation were deactivated, causing failure of the AD. Several bench-scale reactors soured after the introduction of the FW/FOG feed streams. By comparing measurements from stable with measurements from the souring reactors, I identified two different circumstances responsible for souring events. One set of reactors soured rapidly after the introduction of FW/FOG due to the digester’s hydraulic retention times (HRT) becoming too short for stable operation. A second set of reactors soured after a long period of stability due to steady accumulation of fatty acids (FAs) that depleted bicarbonate alkalinity. FA accumulation was caused by the incomplete hydrolysis/fermentation of feedstock protein, leading to insufficient release of ammonium (NH4+). In contrast, carbohydrates were more rapidly hydrolyzed and fermented to FAs. The most important contribution of my research is that I identified several leading indicators of souring. In all cases of souring, the accumulation of soluble chemical oxygen demand (SCOD) was an early and easily quantified indicator. A shift in effluent FA concentrations from shorter to longer species also portended souring. A reduction in the yield of methane (CH4) per mass of volatile suspended solids removed (VSSR) also identified souring conditions, but its variability prevented the methane yield from providing advanced warning to allow intervention. For the rapidly soured reactors, reduced bicarbonate alkalinity was the most useful warning sign, and an increasing ratio of SCOD to bicarbonate alkalinity was the clearest sign of souring. Because I buffered the slow-souring reactors with calcium carbonate (CaCO3), I could not rely on bicarbonate alkalinity as an indicator, which put a premium on SCOD as the early warning. I implemented two buffering regimes and demonstrated that early and consistent buffering could lead to reactor recovery. / Dissertation/Thesis / Masters Thesis East Asian Languages and Civilizations 2020

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

La digestion anaérobie, procédé d’énergie renouvelable, constitue un atout indéniable de récupération des flux matière et énergie des déchets en réponse aux enjeux du développement durable. Ainsi, la présente étude a pour objectif de contribuer à la compréhension des mécanismes qui gouvernent l’environnement réactionnel de digestion en anaérobie et les effets des digestats sur la matrice bio-physico-chimique des sols à vocation agricole. Le développement des tests de lixiviation en réacteurs contrôlés aérobie et anaérobie, les modes de mobilisation du contenu organo-minéral des substrats et la valorisation du biogaz pour l’équarrissage des bêtes ont été réalisés. Les verrous techniques et physico-chimiques entachant la digestion anaérobie des déchets d’ananas ont été levés et optimisés grâce à des co-substrats notamment les bouses de vache et les cendres. Les digestats ont été apportés sur des sols agricoles, des sols des zones de forêts et des milieux sans matière organique ni argiles et ont permis de déceler les limites d’utilisation des digestats et les interactions avec les fractions organiques et minérales du sol. Cette étude montre ainsi, l’importance de développer la filière de méthanisation pour une élimination durable des déchets organiques. / Anaerobic digestion, a renewal energy process, constitutes an undeniable asset of material and energy flows recovering in response to sustainable development issues. Thus, the aim of this current study was to contribute to the understanding of mechanisms that govern the reactive environment of anaerobic digestion and the effects of digestates on the biophysico- chemical matrix of agricultural soils sector. The running of leaching tests in aerobic and anaerobic controlled reactors, organo-mineral mobilizations patterns of the substrates and the valorization of biogas in slaughtered animals knackering have been realized. The physicochemical and technical locks tarnishing the pineapple wastes anaerobic digestion have been lifted and optimized through the co-substrates including cattle manure and ashes. The digestates have been brought on agricultural soils, forests areas soils and medium free of organic matter and clays and allowed to detect the limits of digestates uses and the interactions with organic and mineral fractions of soils. This study, thus show, the importance to develop the anaerobic digestion sector for a sustainable removal of organic wastes.

Anaerobic digestion can be used to sustainably treat the organic byproducts of the biodiesel process (crude glycerol and biodiesel wastewater) while generating a renewable natural gas to be used for heating or electricity generation. The purpose of this thesis was to (1) investigate the possibility of co-digestion of biodiesel byproducts without use of external substrates or pretreatment and (2) assess the impact of various acclimatization rates on the stability and efficiency of such a system. Two inocula (effluent from a wastewater treatment plant digester and from an agro-industrial waste digester) and two acclimatization rates were studied. The results showed that co-digestion of crude glycerol and biodiesel wastewater at high organic loading rates(up to 6.8 g COD L-1day-1)is possible without addition of other substrates or pretreatment.Thecumulative biogas production of the digesters using inoculum from the agro-industrial waste digester was statistically greater than the digesters using the wastewater treatment plant digester, indicating that similar inoculum could be useful for additional experiments.In addition,maximum efficiency due to a slower rate of acclimatization was higher for both inocula, up to a maximum average daily biogas yield of 621 mL biogas g-1COD added.Finally, comparison of two methods for measuring gas production (mass difference and volumetrically using a syringe) revealed a reasonable correlation(R2= 0.97)between the methods. Additional validation could lead to use of the mass difference method as a validation method or an alternative gas production measurement method.

The Brazilian sugarcane and ethanol industries produce lot of waste which has potential for energy production. Anaerobic digestion (AD) can be effectively utilized for producing biogas from these wastes. During the AD process, huge volumes of digestate are produced with some being employed in fertilizer application whilst large volumes are mostly stored in uncovered tanks. This result in emission of residual methane and loss of energy which can be recovered through post- digestion approaches. To analyse optimal utilization of this digestate and enhanced biogas production, co- digestion of post- digestate from a continuously stirred reactor (CSTR) performing co-digestion of sugarcane waste from Brazil (Vinasse, filter cake and straw) with addition of different glycerol concentrations were studied. The addition of glycerol characterised by its biodegradability and high organic content makes it a suitable substrate to enhance biogas production. A biomethane potential was assessed when the digestate was co-digested with 15% and 25% CODg/L of glycerol. The batch test lasted for 39 days. The results demonstrated that, co-digestion of digestate with glycerol has the potential of increasing cumulative methane and biogas yield with 25% addition producing the highest methane and biogas yield (318 Nml/gCOD and 196 Nml/gCOD) which was approximately 6 times higher compared to mono-digestion of the digestate. Anaerobic co-digestion of digestate and glycerol was examined in two lab scale reactors (CSTR) at mesophilic conditions (35oC) and were run for 90 days. The reactor (R1) performing co-digestion increased methane and biogas production by 300% and 170% when glycerol concentrations of 15% and 25% of influent COD were added, respectively. Moreover, there was a decrease in CH4 yield when the reactors were continuously fed with 15% and 25% CODg/L of glycerol. This was an indication that, microorganisms easily digested glycerol addition at the early stages. Glycerol addition (50% CODg/L) resulted in a decrease in CH4 and biogas production.  This result shows, CH4 yields in the post-digester can be enhanced with glycerol addition if it does not exceed a limiting of 50% of the organic loading rates of the feed.

Content: The understanding of how chemical, physical and environmental parameters work during anaerobic digestion production and waste treatment is an important step in improving the efficiency and process stability. This study provides the evolution of the biogas production and the efficiency of the treatment of the anaerobic digestion of solid wastes of tanneries at-line monitored in batch laboratory-scale bioreactors. Leather shavings and sludge from wastewater treatment plants substrates were considered in the study. The findings suggest that AD of the tannery solid waste can be separated into three phases: a long lag phase, a log phase with a low metabolic rate and the final phase where all the shavings were metabolized. Take-Away: The AD of the tannery solid waste can be separated into three phases: a long lag phase, a log phase with a low metabolic rate and the final phase where all the shavings were metabolized

Wastewater treatment performance of three pilot-scale packed-bed anaerobic digesters with walnut shell medium was researched for treating dairy freestall barn flushwater. Reciprocation mixing was evaluated as a means to lessen channelization in the media bed and to improve biogas production and organic matter removal at ambient temperatures. Reciprocation has been used in biological nitrogen removal systems to introduce air into the system to repeatedly oxygenate nitrifying biofilm along with mixing (Behrends et al. 2003), but the anaerobic systems benefit from mixing. Two tanks were used in each system, where one was full and one was empty at any given time. Water was repeatedly pumped from one tank to the other and back again (reciprocation). A key research objective was to determine the minimum reciprocation frequency (between 0-10 per day) while still maintaining moderate methane production and treatment performance. Broken walnut shells with a specific surface area of 360 m2/m3 were used as the packed media. Digester influent, which was pretreated to remove large solids, had the following characteristics: total solids (TS) of 5.5 g/L, volatile solids (VS) of 2.8 g/L, 5-day carbonaceous biochemical oxygen demand (cBOD5) of 800 mg/L, and chemical oxygen demand (COD) of 4340 mg/L. Average digesting liquid temperatures ranged from 14.1 to 23.6 °C. At 6-day theoretical hydraulic residence times (V/Q where V is Lliquid, which is volume of liquid occupying the digester pores, and Q is total daily influent flow) and 1 reciprocation per day, methane production was 0.060 ± 0.10 LCH4/Lliquid-day and at 10 reciprocations methane production 0.058 ± 0.14 LCH4/Lliquid-day (mean ± standard deviation of measurements over time). COD percent removals were both 51% at 6-day V/Q. Since multiple reciprocations did not appear to make a difference in methane production and treatment performance, fewer reciprocations were used in subsequent experiments. Higher flow rates were also used in subsequent experiments to accelerate sludge clogging and channelization in the walnut-shell bed and thereby allow detection of any advantage provided by reciprocation compared to an upflow reactor. At 0 and 1 reciprocations per day and 0.35 and 0.50-day V/Qs, respectively, methane production was 0.24 ± 0.08 and 0.23 ± 0.08 LCH4/Lliquid-day and COD percent removal was 17 and 22%. Over the study period of 226 days, walnut shell porosities decreased due to sludge accumulation from 0.68 and 0.64 (start-up or clean-bed) to 0.31 and 0.24 in the 1 and 0 reciprocation per day reactors. Sludge accumulation and channelization did not appear to be affected by reciprocation mixing on the scale of this study.

La production de biogaz par digestion anaérobie (DA) est une technologie renouvelable de longue date et un bioprocessus en croissance continue. Les matériaux lignocellulosiques (ML) présentent plusieurs caractéristiques qui les rendent particulièrement attrayants parmi les substrats couramment employés dans les bioréacteurs anaérobies. En particulier, les ML sous la forme de résidus agricoles ont été reconnus comme la matière première la plus appropriée pour la production de biométhane en raison de leur haute disponibilité, de leur faible coût, de leur durabilité et de leur absence de concurrence directe avec la production alimentaire. Cependant, leur récurrence à la conversion biologique entrave leur application pour la production à grande échelle de biogaz et nécessite une étape de prétraitement pour améliorer la dégradabilité microbienne. En plus des défis posés par la structure lignocellulosique, la fourniture de oligo-éléments (OE) a souvent été jugée insuffisante dans les digesteurs de biogaz. La croissance microbienne dépend de la disponibilité et de la quantité optimale de plusieurs OE spécifiques, constituants essentiels des cofacteurs dans les systèmes enzymatiques impliqués dans la biochimie de la formation de méthane. Différents prétraitements chimiques, à savoir le N-méthylmorpholine-N-oxyde (NMMO), le procédé organosolv et un prétraitement alcalin à l'aide de NaOH ont été étudiés pendant plusieurs expériences en lots pour améliorer les rendements de production de biogaz différents peau, coquille de fève de cacao et paille de blé). Les changements dans la cristallinité de la cellulose, la valeur de rétention d'eau et la composition chimique ont été évalués pour mieux évaluer l'effet des différents prétraitements étudiés sur la structure lignocellulosique. En outre, l'addition de différentes doses de Fe, Co, Ni et Se sur la DA de paille de riz a été étudiée, évaluant l'influence de l'origine de l'inoculum, ainsi que la performance et l'effet synergique de la combinaison d'un prétraitement alcalin avec addition de trace éléments avant la DA de paille de riz. La biodisponibilité des OE lors des tests de potentiel de biométhane par lots a également été évaluée en appliquant une technique d'extraction séquentielle. Les trois prétraitements étudiés étaient des méthodes efficaces pour améliorer la production de biométhane à partir des LM utilisées. Le rendement en biométhane de la DA de paille de riz a augmenté de 82 et 41% respectivement après le NMMO et le prétraitement organosolv. Comparé à la même expérience, le prétraitement NMMO, organosolv et NaOH a permis d'améliorer la DA de la paille de blé, ce qui affecte différemment la composition chimique de la LM brute. Le rendement cumulatif de production de biométhane de 274 mL de CH4/g VS obtenu avec la paille de blé non traitée a été augmenté de 11% par le prétraitement du NMMO et de 15% par le prétraitement organosolv et alcalin. Les coquilles de noisettes et de fèves de cacao, qui n'avaient jamais été étudiées auparavant comme substrats AD, présentaient un bon potentiel de production de biogaz, avec des rendements cumulatifs de biométhane respectivement de 223-261 et 199-231 mL CH4/g VS pour les charges non traitées. Cependant, les prétraitements à la fois de NMMO et d'organosolv n'ont pas conduit à une amélioration significative des rendements de production de biométhane de ces deux LM. La supplémentation des OE n'a eu qu'un effet mineur par rapport aux méthodes de prétraitement. L'ajout de Fe, Co, Ni et Se n'a pas entraîné d'amélioration significative de la DA de paille de riz, alors que l'utilisation du prétraitement de NaOH au cours de la même expérimentation a provoqué une augmentation considérable de la DA, augmentant la production de biogaz de 21%. L'effet négligeable observé après la supplémentation des OE sur la paille de riz pourrait être lié à sa structure lignocellulosique complexe qui nécessite une amélioration de l'hydrolyse qui est l'étape limitante / Biogas production via anaerobic digestion (AD) is a long-standing renewable technology and a continuously growing bioprocess worldwide. Lignocellulosic materials (LMs) present several features that make them especially attractive among the organic substrates commonly employed in anaerobic bioreactors. In particular, LMs under the form of agricultural residues have been acknowledged as the most suitable feedstock for biomethane production due to their high availability, low cost, sustainability and no direct competition with food and feed production. However, their recalcitrance to biological conversion hinders their application for full-scale production of biogas and requires a pretreatment step to improve the LM microbial degradability. In addition to the challenges posed by the lignocellulosic structure, the supply of trace elements (TEs) has often been found insufficient within biogas digesters. The microbial growth depends on the availability and optimal amount of several specific TEs, which are essential constituents of cofactors in enzyme systems involved in the biochemistry of methane formation. Different chemical pretreatments, namely the solvent N-methylmorpholine-N-oxide (NMMO), the organosolv process, and an alkaline pretreatment using NaOH, were investigated during several batch experiments to enhance the biogas production yields from different LMs (i.e. rice straw, hazelnut skin, cocoa bean shell and wheat straw). Changes in the cellulose crystallinity, water retention value and chemical composition were assessed to better evaluate the effect of the different pretreatments studied on the lignocellulosic structure. Furthermore, the addition of different doses of Fe, Co, Ni and Se on the AD of rice straw was studied, evaluating the influence of the inoculum origin, as well as the performance and synergistic effect of combining an alkaline pretreatment with the addition of trace elements prior to the AD of rice straw. The bioavailability of TEs during batch biomethane potential tests was also evaluated applying a sequential extraction technique. The three pretreatments investigated were effective methods for enhancing the biomethane production from the employed LMs. The biomethane yield from the AD of rice straw increased by 82 and 41% after the NMMO and organosolv pretreatment, respectively. When compared within the same experiment, the NMMO, organosolv and NaOH pretreatment were able to improve the AD of wheat straw, differently affecting the chemical composition of the raw LM. The cumulative biomethane production yield of 274 mL CH4/g VS obtained with the untreated wheat straw was enhanced by 11% by the NMMO pretreatment and by 15% by both the organosolv and alkaline pretreatment. Hazelnut skin and cocoa bean shell, which were never investigated before as AD substrates, showed a good potential for biogas production, with cumulative biomethane yields of 223-261 and 199-231 mL CH4/g VS, respectively, for the untreated feedstocks. However, both NMMO and organosolv pretreatments did not lead to a significant enhancement of the biomethane production yields from these two LMs. The TE supplementation had only a minor effect compared to the pretreatment methods. The addition of Fe, Co, Ni and Se did not result in a significant improvement of the AD of rice straw, whereas the use of the NaOH pretreatment, during the same batch experiment, caused a considerable enhancement of the AD, increasing the biogas production yield by 21%. The negligible effect observed after TE supplementation on the AD of rice straw could be linked to its complex lignocellulosic structure, which requires an enhancement of the hydrolysis, which, rather than the methanogenesis, is the rate-limiting step

Das Ziel dieser Arbeit ist es biobasierte, bioabbaubare Biokunststoffe mit einfacher Prozesstechnik zu desintegrieren und für anaerobe Mikroorganismen verfügbar zu machen. Mittels der Ergebnisse der Untersuchungen soll nachgewiesen werden, dass eine anaerobe Verwertung der desintegrierten Biokunststoffe bzw. der generierten Flüssigkeiten möglich ist. Außerdem soll ermittelt werden, welches energetische Potenzial dabei freigesetzt wird. Im Rahmen einer Wirtschaftlichkeitsbetrachtung wird die Implementierung einer Desintegrationsstufe in einer Vergärungsanlage bewertet. Zu Beginn der Untersuchungen wird festgestellt, dass eine anaerobe Verwertung im mesophilen und im thermophilen Bereich nur unzureichend realisierbar ist. In den anschließenden Untersuchungen werden Maßnahmen zur Beschleunigung der Desintegration von zertifizierten bioabbaubaren Biokunststoffen untersucht. Nachdem ein Nachweis der Desintegration verschiedener Biokunststoffe erbracht und aus-reichend hohe Gehalte gelöster Organik nachgewiesen werden, erfolgt im Anschluss die anaerobe Verwertung der erzeugten Flüssigkeiten in einer mesophilen, kontinuierlichen Vergärung. Die Gärtests geben Aufschluss über die Vergärbarkeit, das Biogaspotenzial, die Biogasqualität und die Abbaugrade der desintegrierten Biokunststoffe. Der höchste Abbaugrad (71,3 %) wird bei der Untersuchung der Flüssigkeiten der Ecovio®-Biobeutel erreicht. Der Abbau der Activia®-Becher (39,6 %) verlief weniger effizient und wird durch hohe Gehalte organischer Säuren und Verdünnungseffekte beeinflusst. Die real erzeugten Biogaspotenziale schwanken zwischen 0,1 lN CH4/g CSB und 0,23 lN CH4/g CSB. Die Biogasqualität während der Versuche ist sehr gut. Die Verhältnisse von CH4 zu CO2 liegen überwiegend zwischen 50:50 und 60:40. Der Nachweis der energetischen Nutzbarmachung der desintegrierten Biokunststoffe für den mikrobiellen Umsatz bzw. zur Biogasbildung wird erbracht. Die Implementierung einer Desintegrationsstufe in eine bestehende Vergärungsanlage wird im Hinblick auf die Wirtschaftlichkeit bewertet. Die Implementierung ist technisch realisierbar. Die Kosten der Implementierung übersteigen die Erlöse um ein Vielfaches. Auch bei längeren Betrachtungszeiträumen kann kein Gewinn erwirtschaftet werden.

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