The objective of this research was to design an alternative wastewater treatment system for turkey processing plants to recover energy and reduce N and P to allowable discharge levels. The objective included: 1. Determine the quantity and quality of biogas produced from the turkey processing wastewater (TPW) and COD reduction efficiency. 2. Design a waste treatment system and validate proof of concept for simultaneous P and N removal with a goal of attaining effluent concentrations of 0.1 mg/L and 4 mg/L, for P and N, respectively. A lab-scale complete mixed anaerobic digester was used for turkey processing wastewater (TPW) digestion and biogas recovery running for 6 months. Along with the anaerobic digester, a two-sludge system called A2N-SBR consisting of an anaerobic-anoxic sequencing batch reactor and an attached growth post-nitrification reactor was added for biological nitrogen and phosphorus removal running for 3 months. Biogas production yields of 778 + 89 mL/gVSadded and 951.30 mL/g COD were obtained through anaerobic digestion. Also, an energy balance was conducted on a pilot scale digester for a turkey processing plant with wastewater production of 2160 m3/d and using a combined heat and power (CHP) enginefor conversion of biogas to heat and electricity. Although the biogas yield achieved in a complete mixed reactor was relatively lower than yields obtained in previous studies using reactors such as UASB, still a complete mixed reactor can be a good choice for biogas recovery from TPW and can be used for codigestion with some specific turkey processing byproducts for biogas recovery. Nitrogen and phosphorus removal in the A2N-SBR system were 47% and 75%, respectively, and during the study the nitrogen and phosphorus removal mean concentration in effluent did not meet the nutrient limits specified in the objectives. Average TP and TN in the effluent were 3.2 mg/L and 137 mg/L, respectively. Throughout the study, the nitrification reactor biofilm was not completely developed. Incomplete nitrification and poor settling might be the reasons that quality obtained in effluent was low. To improve the process condition in A2N-SBR, online monitoring of pH, dissolved oxygen (DO) and oxidation reduction potential (ORP) can help to optimize each stage in the SBR and stages duration can be set based on the results. / Master of Science

Biogas is of growing interest in Sweden, and a public inquiry suggested the government to set a goal of producing 10 TWh biogas in 2030 although only 2 TWh biogas was produced in Sweden in 2018 (Regeringskansliet, 2019) (Klackenberg, 2019). To achieve this optimistic goal and to meet the increased demand of biogas, new biogas production facilities needs to be built. The purpose of this report is to investigate the economic feasibility for the development of a biogas recovery process adjoined to an incineration facility in Sweden. The report first gives an overview of the largest incineration facilities in Sweden. The largest quantity of food waste was estimated in Gothenburg to be 56´744 WRQ SeU \eaU. For the economic feasibility, a conceptual facility was constructed with 169´000 ton residual waste per year of which 45´000 ton was food waste. A biogas process model was built in Excel where the biogas potential was calculated using characteristics for food waste. The annual production of liquid biogas was estimated to 43´970 MWK. The economic evaluation was based on the conceptual facility. In the baseline scenario the incomes for the process was the value of liquid biogas, 25,6 MSEK per year, a Gate-fee synergy of 5 MSEK per year and a Tax deduction synergy of 1 MSEK per year. The investment cost was estimated to 211,6 MSEK and the Operation & Maintenance cost was estimated to 6,3 MSEK per year. This resulted in an NPV of 69,5 MSEK and an IRR of 10,3% for the project, indicating a profitable investment. Three different scenarios were considered, apart from the baseline scenario, where the first excluded all synergies with the incineration facility, which generated an NPV of 2,3 MSEK. The second scenario only considered the minimal gate-fee synergy which gave an NPV of 37,8 MSEK. Finally, the third scenario where all synergies were included, and an additional investment grant was introduced gave the project an NPV of 111,8 MSEK. A sensitivity analysis was also conducted which showed that the input of food waste treated, weighted average cost of capital and potential grants had the biggest impact on the financial results. None of the results from the sensitivity analysis showed a negative NPV. / Intresset för biogas växer i Sverige och i en statlig utredning föreslogs regeringen att sätta upp ett mål att producera 10 TWh biogas 2030 (Regeringskansliet, 2019). Detta kan jämföras med 2018 då endast 2 TWh producerades (Klackenberg, 2019). För att uppnå detta optimistiska mål och för att möta den ökade efterfrågan på biogas behöver nya produktionsanläggningar byggas. Syftet med denna rapport är att undersöka de ekonomiska möjligheterna för utvecklingen av en biogasanläggning angränsad till en förbränningsanläggning i Sverige. Rapporten ger först en översikt över de största förbränningsanläggningarna som behandlar hushållsavfall i Sverige. Det uppskattades att den största mängden matavfall som går till förbränning i Sverige är i Göteborg där 56´744 ton matavfall förbränns per år. För att bestämma de ekonomiska förutsättningarna konstruerades en konceptuell anläggning som behandlar 169´000 ton restavfall per år varav 45 000 ton består av matavfall. En biogasprocess modellerades i Excel där den potentiella biogasen beräknades baserat på matavfallets karaktäristik. Slutligen uppskattades den årliga produktionen av flytande biogas till 43´970 MWh. Den ekonomiska utvärderingen baserades på den konceptuella anläggningen. I grund-scenariot bestod inkomsterna för av den flytande biogasen som motsvarade 25,6 MSEK per år, en ´gatefee´-synergi på 5 MSEK per år och en ´skatteavdrags´-synergi motsvarande 1 MSEK per år. Investeringskostnaden uppskattades till 211,6 MSEK och Operation & Maintenancekostnaderna uppskattades till 6,3 MSEK. Detta gav projektet ett nettonuvärde på 69,5 MSEK och en internränta på 10,3% vilket indikerar en lönsam investering. Vidare undersöktes även tre olika scenarier, utöver grund-scenariot, där det första utesluter alla synergier vilket gav ett nettonuvärde på 2,3 MSEK. Det andra scenariot beaktade endast den minimala ´gate-fee´-synergin vilket gav ett nettonuvärde på 37,8 MSEK. Det tredje scenariot inkluderade alla synergier samt ett investeringsbidrag vilket resulterade i ett nettonuvärde på 111,8 MSEK. En känslighetsanalys genomfördes också som visade att tillförseln av behandlat matavfall, kapitalkostnaden och potentiella investeringsbidrag hade den största påverkan på de finansiella resultaten. Inget av resultaten från känslighetsanalysen visade ett negativt nettonuvärde.

Le biogaz est une source d’énergie renouvelable, dont le potentiel est insuffisamment valorisé à l’heure actuelle. Avant toute valorisation énergétique, des traitements épuratoires coûteux (e.g. adsorption par des charbons actifs imprégnés, CAI) sont nécessaires, limitant la rentabilité économique. Un intérêt vers le développement de procédés de traitement « bon marché » est mis en évidence au travers d’études, la plupart à l’échelle du laboratoire, basées sur l’utilisation de déchets/sous-produits. Nous avons ainsi réalisé une étude de faisabilité d’un procédé d’élimination d’H2S, composé très corrosif et toxique, par des Mâchefers d’Incinération de Déchets Non Dangereux (MIDND). Une unité pilote a été installée sur la plateforme de valorisation de biogaz d’une installation de stockage de déchets non dangereux. Des essais à petite échelle (500 g) ont permis le screening de 6 différents MIDND et l’identification des paramètres influents sur le traitement d’H2S. Le transfert d’échelle (10 kg), ainsi que des conditions opératoires optimisées, ont permis d’obtenir une capacité d’adsorption des MIDND supérieure à 200 gH2S/kgMS, proche de celle de certains adsorbants commerciaux. Ce travail expérimental a été complété par un questionnement scientifique sur les mécanismes de rétention d’H2S. Un panel de techniques analytiques a permis de caractériser la matrice (avant et après traitement), de réaliser les bilans de soufre et d’identifier sa spéciation. Le mécanisme proposé repose majoritairement sur l’oxydation catalytique d’H2S en soufre élémentaire dans un contexte physico-chimique adéquat (humidité, pH, porosité, présence d’O2 et de métaux). L’intérêt économique de la mise en œuvre industrielle du procédé de désulfuration avec des MIDND a été démontré, avec une réduction conséquente des coûts de traitement par rapport à l’utilisation de CAI. Ce travail montre également l’intérêt environnemental d’un tel procédé qui entre parfaitement dans le cadre de l’économie circulaire. / Biogas is a renewable energy source, which potential is still under-evaluated. Before any energy production from biogas, costly purification treatments (e.g. adsorption by impregnated activated carbons, IAC) are necessary, limiting the economic profitability. An increasing interest in the development of "low-cost" treatments based on the use of waste/by-products is shown by several studies, most of all by tests at laboratory scale. Thus, a feasibility study of the use of Municipal Solid Waste Incineration (MSWI) Bottom ash (BA) for the removal of H2S, a very corrosive and toxic compound in biogas, has been carried out in this thesis. An experimental pilot was installed on an energy recovery plant from biogas produced in a landfill (non-hazardous waste). Small-scale trials (500 g) allowed the screening of 6 different BAs and the identification of key parameters of the desulfurization. The transfer to a bigger scale reactor (10 kg), as well as the optimized operating conditions, enabled to obtain an adsorption capacity higher than 200 gH2S/kgdy BA, similar to that of some commercial adsorbents. The on-site experimental study has been completed by a scientific investigation on the mechanisms involved on the H2S retention by BA. Several analytical techniques were used to characterize the material before and after the biogas treatment, to carry out the sulfur mass balances and to identify its chemical speciation. The proposed mechanism relies predominantly on the catalytic oxidation of H2S to elemental sulfur, in an adequate physicochemical context (moisture, pH, porosity, O2 and metal oxides). The economic benefit of an industrial implementation of the desulfurization treatment with MIDND has been demonstrated. The operational costs are reduced compared to a treatment with IAC. The environmental value of such a treatment is also shown and fits perfectly into a circular economy framework.

Au cours de cette thèse, les prévisions de la méthodologie d’Analyse de Cycle de Vie (ACV) sont améliorées, via l’exergie, pour l’analyse et l’éco-conception des procédés. Nous mettons l’accent sur le potentiel de l’analyse exergétique et de la Consommation d’Exergie Cumulée (CExC) dans l’évaluation du critère d’épuisement, de productivité et de recyclabilité des ressources naturelles. Dans ce cadre, les transferts de pollutions et les impacts environnementaux d’un système de traitement des eaux résiduaires (STEP) ont été analysés en relation avec l’exergie consommée (CExC) et de l’exergie détruite (étude a priori). L’étude montre que la décision est différente lorsque l’indicateur d’épuisement des ressources naturelles est basé sur la méthode CExC de celle basée sur la méthode CML. L’amélioration de l’éco-efficacité d’une STEP implique un recyclage des boues en agriculture. La stabilisation des boues par digestion anaérobie réduit le volume des boues et ainsi l’impact du transport en comparaison avec la stabilisation à la chaux. Toutefois, elle réduit le potentiel fertilisant des boues, d’une part, et augmente la consommation d’énergie et l’impact du réchauffement climatique à cause du traitement des retours en tête d’autre part. Bien que la valorisation du biogaz en cogénération réduise la dépendance énergétique de la STEP et améliore son éco-efficacité globale en comparaison avec le chaulage, elle n’offre pas la possibilité à un séchage des boues. Le séchage des boues constitue l’une des recommandations des agriculteurs, bien qu’il n’améliore pas le l’éco-efficacité globale de la STEP, en augmentant l’épuisement et l’exergie détruite des ressources brutes et du biogaz / The focus of the work has been to improve the predictions of Life Cycle Assessment (LCA) via exergy for processes analysis and eco-design. The potential of the exergetic analysis and Cumulative Exergy Consumption (CExC) in estimating the criterion of depletion, productivity and recyclability of natural resources has been investigated. In this context, the transfer of pollutants and the environmental impacts of a wastewater treatment system (WWTP) have been analyzed in relation with the consumed exergy (CExC) and the destroyed exergy. The study shows that decision is different if the indicator of depletion of natural resources is based on the method of CExC or on the CML method. The improvement of the overall eco-efficiency of a WWTP involves a recycling of sludge in agriculture. Stabilization of sludge by anaerobic digestion reduces the volume of sludge and consequently the impact of transport in comparison with the stabilization with lime. However, on one hand, it reduces the fertilizer potential of sludge. On the other hand it increases energy consumption and the impact of the global warming because of the treatment of digested sludge supernatant recycled to the WWTP. Although the recovery of biogas by cogeneration reduces the energy dependency of the WWTP and improves its overall eco-efficiency in comparison with the liming scenario, it does not provide the possibility for sludge drying. Drying the sludge is one of the recommendations of farmers, although it does not improve the overall eco-effectiveness of the WWTP, and increases the depletion and the destroyed exergy of raw resources and biogas