In Canadian remote northern communities most electricity is generated by burning diesel fuel. However, because it is expensive to import fuel into remote communities the cost of electricity is very high. Waste management is also difficult in remote northern communities. The goal of this thesis was to investigate the co-gasification of refuse waste materials and biomass as a means of reducing solid waste volumes while also using locally available materials for power generation. As part of this research, thermo-gravimetric analysis (TGA) was investigated as a potential means of characterizing refuse derived fuels (RDF). Laboratory sample preparation of RDF for TGA had not been thoroughly considered. Laboratory sample preparation is important since RDF is very heterogeneous compared to other solid fuels and since TGA typically requires a very small sample size. A TGA method was applied to a variety of materials prepared from a commercially available RDF using a variety of procedures. The repeatability of the experimental results was related to the sample preparation methods. Cryogenic ball milling was found to be an appropriate means of preparing RDF samples for TGA. Applicability of the TGA method to the determination of the renewable content of RDF was considered. Air-blown auto-thermal gasification experiments using materials representative of waste and biomass were performed at 725°C, 800°C, and 875°C, using a 0.15 m internal diameter bubbling fluidized bed gasifier located at NRCan CametENERGY in Ottawa, Ontario. Commercially prepared RDF and PET scrap were used to represent waste materials. Commercially produced hardwood pellets were used to represent biomass. The co-gasification of hardwood pellets and commercially produced RDF indicated that each fuel make a contribution to the results which is proportional to its fraction in the feed mixture. Inclusion of the RDF in the fuel mixture led to bed agglomeration at the 875°C temperature condition. Higher temperatures were found to provide better conversion of the fuel to gas, and the limitation which inclusion of RDF places on the operating temperature of the gasifier negatively affects conversion of biomass. Results obtained with RDF suggested that utilization of mixed waste for a thermal conversion process located in a Canadian remote northern community is probably not a viable option. It was then decided to target plastic waste in particular. Plastic could be source-separated, collected, and gasified alongside biomass. Polyethylene terephthalate (PET), which is often used for food and beverage containers, was chosen to represent plastic. Initially, attempts were made to co-gasify mixtures of PET pellets and hardwood pellets. These attempts failed due to the formation of coke above the bed. To alleviate these problems hardwood-PET composite pellets were manufactured and these were gasified at 725°C, 800°C, and 875°C. Inclusion of PET in the pellets dramatically increased the amount of tar produced during gasification.

Fossil fuel depletion, economic development, urban expansion and climate change present tough challenges to municipal- and regional-scale energy systems. Regional energy system planning, including waste treatment, renewable energy supply, energy efficiency, and climate change, are considered essential to meet these challenges and move toward a sustainable society. This thesis includes studies on energy system from municipal waste, potential for a fossil fuel-independent regional energy system with increased renewable energy products using waste as one of energy sources, and the performance of biomass-fired combined heat and power (CHP) plants. A top-down method is adopted to organize the studies, from national waste-to-energy (WtE) scenarios to individual energy plants. The first study considers the overall potential contribution of WtE to energy supply and greenhouse gas (GHG) emissions mitigation in Sweden until 2050 under several different scenarios. Depending on WtE scenario considered, the study shows that WtE can supply energy between 38 and 186 TWh and mitigate between CO2 of 1 and 12 Mt per year by 2050 based on the baseline of year 2010. At a regional level, static and dynamic optimization models with a focus on WtE are developed for two regions in Sweden and Finland. The former is used to investigate the possibilities of optimal positioning of new energy plants, retrofitting existing energy plants and planting energy crops. The latter case study is on regional heat and power production using biogas generated from agricultural and livestock wastes. Centralized biogas production units perform better than distributed production regarding energy and carbon balance though the net energy output is negligible. However, a significant GHG emission can be reduced compared to the present status. Retrofitting existing conventional CHP plants is another option for improving regional energy system. The study shows that integrating heat-demanded processes such as drying, bioethanol and pellet production with existing CHP plants can improve overall energy efficiency and power output, increase annual operation time and reduce production cost as well as mitigate GHG emissions.  It is recommended that building new WtE/energy plants at optimum sites, upgrading the existing energy plants, expanding the agricultural/forestry waste/residues output (biomass) and planting more energy crops shall be taken into considerations for the future regional energy systems. / Utarmning av fossila bränslekällor, ekonomisk utveckling, städernas utbredning och klimatförändring är svåra utmaningar för kommunala- och regionala energisystem. Planering av det regionala energisystemet, inklusive avfallshantering, förnyelsebara energikällor, energieffektivisering och hänsyn till klimatförändringar, anses avgörande för att möta dessa utmaningar och gå mot ett hållbart samhälle. Denna avhandling innehåller studier av energisystem centrerad kring hushållsavfall, potentialet för fossilbränslefria regionala energisystem som utnyttjar ökad andel förnyelsebara energiprodukter med avfall som en energikälla och prestandautvärdering av ett biomassa-eldat kraftvärmeverk. Studierna har organiserats efter storlek på system, från nationella avfall-till-energi scenarier till enskilda kraftverk.   Den första studien behandlar övergripande möjligheten att genom avfall-till-energi bidra till energiförsörjningen och begränsa utsläppet av växthusgaser i Sverige till 2050 under flera olika scenarier. Beroendet på avfall-till-energiscenario visar studien att genom att utnyttja avfall kan mellan 38 och 186 TWh energi levereras och dessutom kan koldioxidutsläppen reduceras med 1-12 miljoner ton till år 2050 med 2010 som basår.   På den regionala nivån, statiska och dynamiska optimeringsmodeller, med fokus på avfall-till-energi, är utvecklats för två regioner, en i Sverige och en i Finland. Det första modellen används för hitta den optimala placeringen av nya energianläggningar, anpassning av befintliga anläggningar och placering av odlingar av energigrödor. Den senare ingår i en fallstudie av den regionala kraft- och värmeproduktionen genom utnyttjande av biogas producerad från jordbruksavfall och djurgödsel. Centraliserade biogasanläggningar presterar bättre än decentraliserad anläggningar när det gäller energi – och kolbalanser även om i båda fallen så är skillnaden mellan konsumerad mängd bränsle, värme och el och producerad värme och el försumbar. Däremot kan en betydande mängd av växthusgasutsläppet i båda fallen undvikas jämfört med nuläget.   Anpassning av befintliga konventionella kraftvärmeverk är ett annat alternativ för att förbättra det regionala energisystemet. Studien visar att genom att integrera värmekrävande processer såsom torkning, bioetanol- och pelletsproduktion med befintliga kraftvärmeverk kan den totala energieffektiviten och uteffekten förbättras, öka den årliga drifftiden och minska produktionskostnaderna och utsläppen av växthusgaser.   Rekommendationen är att för de framtida regionala energisystemen överväga att bygga nya avfall-till-energianläggningar med optimal placering, uppgradera befintliga energianläggningar utöka insamlandet av avfall/restprodukter från jord- och skogbruk och plantera mer energigrödor.

Waste can be considered as an urban burden or as a valuable resource depending on how it ismanaged. Different waste treatment technologies are available at present to manage municipal solidwaste (MSW). Various actors are involved to develop waste treatment technology for certain area.The aim of this study is to analyze the driving forces in technical development in waste sector inSweden. The study is also done to identify emerging waste management technology in Sweden.Moreover, a comparative study of existing and emerging technologies is done by Life CycleAssessment (LCA) model. An extensive literature review and pilot questionnaire survey among thewaste management professionals’ is done for the study. LCA model is developed by SimaProsoftware CML2 baseline method is used for identifying environmental burden from the wastetechnologies.Dry composting, Pyrolysis-Gasification (P-G), Plasma-Arc are identified as potential emergingtechnologies for waste management system in Sweden. Technical developments of thesetechnologies are influenced by indigenous people’s behavior, waste characteristics, regulations, healthor environmental impact and global climate change. Comparative LCA model of P-G andIncineration shows that, P-G is a favorable waste treatment technology than Incineration for MSW,especially in acidification, global warming and aquatic eco-toxicity impact categories.

Curitiba is a city of two million inhabitants located in the South of Brazil. It is a pioneer in waste management in the country, and is famous for its programs promoting recycling and organic waste collection. The city is now willing to take waste management one step further by investigating new solutions to treat and recover energy from organic municipal solid waste. This report is the fruit of a collaboration between two departments of the municipality of Curitiba, four local universities, the Swedish environment protection agency and the Royal Institute of Technology – KTH. The purpose of this report is to assess the potential for the development of anaerobic digestion as a solution to treat the organic municipal solid waste generated in Curitiba. The report offers an overview of the current waste treatment and of the main sources of organic waste in Curitiba. The annual amount of organic waste generated in the city is estimated to 144,350 tons, of which 913 tons come from food markets supervised by SMAB, the secretary of food supply. Three different scenarios, corresponding to three ranges of waste sources, have been considered. In the first one, the organic wastes generated by one of the two public markets of Curitiba are treated on-site. In the second one, all the organic wastes from food markets, street markets and popular restaurants are treated together in a medium-scale anaerobic digester. In the third one, all the sources of organic municipal solid waste identified in Curitiba are considered, including residential, institutional and small commercial waste. The annual methane production is estimated to 5,400 m3, 86,000 m3 and 12,600,000 m3 respectively for the three scenarios. In the last two scenarios, the methane could be converted into electricity, resulting in an annual electricity production of 257 MWh and 37,600 MWh. The first scenario does not consider a post-treatment of the digestate remaining at the end of the digestion. Between 46 and 50 tons of digestate could be used as a liquid fertilizer on-site and the surplus could be sold. For the two other scenarios, the digestate would be dewatered and composted to be sold as a dry fertilizer. The dry fertilizer production is estimated to 386 tons and 63,000 tons respectively every year. Each of the scenario considered would be financially viable, with a discounted payback period varying from 8 months for the small-scale scenario, to over 15 years for the second scenario. The third scenario would be the most lucrative, with a net present value of about 150 million reals. / Curitiba i Södra Brasilien är en stad med två miljoner invånare som har positionerat sig som pionjär inom avfallshantering. Staden är känd i landet med sin främjande strategi för återvinning och organisk avfallshantering. Curitiba planerar att undersöka och experimentera med nya metoder för behandling av avfall kombinerad med energiåtervinning från kommunalt organiskt avfall. Denna rapport är resultat av ett samarbete mellan två avdelningar inom Curitibas kommun, fyra lokala universitet, Sveriges miljöskyddsmyndighet och den Kungliga Tekniska Högskolan. Syftet med denna rapport är att utvärdera den potentialen som den anaeroba nedbrytningen har som medel för behandling av det kommunala fasta avfallet som genereras i Curitiba. Rapporten går även igenom hur avfallshanteringen ser ut i staden i dagsläget samt sammanfattar de största källorna för organiskt avfall i Curitiba. Den årliga mängden organiskt avfall som produceras i staden uppskattas till 144 350 ton, varav 913 ton kommer från livsmedelsaktiviteter som övervakas av det brasilianska livsmedelsverket SMAB. Tre olika scenarier representeras i denna rapport och omfattar tre områden av avfallskällor. I det första scenariot behandlas det organiska avfallet som genereras av en av de två köpmarknaderna i Staden direkt på plats. I det andra behandlas allt organiskt avfall från livsmedelsmarknader, gatumarknader och populära restauranger tillsammans i en medelstor anaerob kokare. I det tredje beaktas alla källor till organiskt kommunalt avfall som identifierats i Curitiba, inklusive bostads-, institutionellt och litet kommersiellt avfall. Den årliga metanproduktionen uppskattas till 5 400 m3, 86 000 m3 respektive 12 600 000 m3 för de tre scenarierna. I det andra och tredje scenariot kunde metan omvandlas till el, vilket resulterade i en årlig elproduktion på 257 MWh respektive 37 600 MWh. I det första scenariot anses inte en efterbehandling av digestatet kvar vid slutet av matsmältningen. Mellan 46 och 50 ton digestat kan användas som flytande gödselmedel på plats och överskottet kan säljas. För de två andra scenarierna skulle digestatet avvattnas och komposteras för att senare säljas som torr gödsel vars produktion beräknas uppgå till 386 ton respektive 63 000 ton varje år. Alla tre scenario som presenteras i denna rapport anses vara ekonomiskt genomförbara med en diskonterad återbetalningstid som varierar mellan 8 månader för det första scenariot till över 15 år för det andra scenariot. Det tredje scenariot anses vara det mest lukrativa med ett nuvärde på ca 150 miljoner realer.