Sustainable waste management remains a great challenge for many cities throughout the world. Landfilling is worldwide the most common way of treating municipal solid waste (MSW) and landfilling of organic matter releases the high potent gas methane, which contributes to global warming. If the biogas instead is collected, either from landfills or produced in a more optimal and controlled environment, it can be used as a fuel to substitute fossil fuels. In this thesis, these sorts of systems are referred to as biogas solutions. In Brazil, the eight largest economy in the world and by far the largest economy in Latin America, landfilling of MSW is essentially the only way MSW is disposed of. Rio de Janeiro, the second largest city of Brazil, have had long issues with waste management, with up until 2012 deposing waste to one of the largest open landfills in the world. This study was done in collaboration with Biogas Research Center (BRC): a national biogas competence center with interests in the Brazilian biogas sector as well as contacts with the Federal University of Rio de Janeiro. Furthermore, as Swedish organic waste management practices are globally in the front edge, the Swedish perspective of waste management combined with local knowledge, could be valuable to find more efficient means of managing residues. Before initiating an actual biogas project, it is reasonable to perform an early assessment. This thesis aimed to perform an early assessment of the biogas sector in Rio, which was carried out by utilizing a multi-criteria framework. The framework consists of four categories (potential, feasibility, economic- and environmental performance), 14 key areas and 59 sub-questions, which helped gather, structure and assess information. An eight-week field study in Rio de Janeiro was part of the study. The results show that no full separation of organic content is performed as source in Rio, which is why the study included the waste streams of mixed MSW (disposed in landfills) and partly sorted organic waste (approximately 85 % organic content; referred to as Waste with High Organic Content, WHOC). Sewage sludge from wastewater treatment plants was excluded from the study to enable a focus on MSW. Potential and feasibility are significantly higher for MSW compared to WHOC, although the authors argue WHOC (or even fully sorted organic waste) have substantial growth opportunities. The landfill receives approximately 1.2 million tonnes of organic wet waste per year and provides a biogas yield of 140 million Nm3 / year (50 – 55 % CH4); whereas 26 – 42 thousand tonnes of dry matter (DM) per year can be collected from WHOC, with a biogas yield potential of 6.6 – 19.5 million Nm3 / year (55 – 63 % CH4). The feasibility analysis showed that all key areas – competing applications, legislation and infrastructure – except economic instruments, are better rated for biogas production from MSW compared to WHOC. The most feasible area of use for the biogas in Rio de Janeiro was deemed to inject the gas in into the grid. The indicated environmental performance shows that injection of biogas to the gas grid reduces GHG emissions with 68 %; and for every tonne of DM digestate, approximately 8 kg phosphorous and 36 kg nitrogen can be replaced. The economic performance shows that biogas production from the landfill is more cost-efficient than from a bioreactor, however none of the biogas productions in Rio de Janeiro is profitable, which usually is expected of a waste management system. The study concludes with identifying several challenges the biogas sector in Rio will be facing: a lack of supply of biogas and no plan in action for increasing demand; economic challenges indicating need for investment support; and a lack of value chain for biofertilizers. The results of the study can hopefully provide stakeholders with a better understanding of opportunities and challenges with biogas solutions in Rio de Janeiro municipality, that ultimately can increase the chance for successful implementation in the region. / Hållbar avfallshantering är fortsatt en stor utmaning för många städer runtom i världen. Deponering är globalt sett det vanligaste sättet att göra sig av med fast kommunalt avfall och deponering av organiskt avfall avger den potenta gasen metan, som bidrar till global uppvärmning. Om biogasen istället samlas upp, antingen från deponin eller produceras i en mer optimal miljö, kan gasen istället användas som bränsle för att substituera fossila bränslen. I denna rapport kallas denna typen av system för biogaslösningar. I Brasilien, världens åttonde största ekonomin och den avsevärt största ekonomin i Latinamerika, hanteras fast kommunalt avfall i princip endast genom deponering. Rio de Janeiro, Brasiliens nästa största stad, har länge haft problem med avfallshantering, som fram tills 2012 slängde allt sitt avfall i en av världens största öppna deponier. Denna studie genomfördes i samarbete med Biogas Research Center (BRC): ett nationellt kompetenscenter inom biogas med intresse av den Brasilianska biogassektorn, samt med kontakter till det federala universitetet i Rio. Eftersom Sverige ur ett globalt perspektiv ligger i framkant vad gäller hantering av organiskt avfall, kan den svenska synvinkeln av avfallshantering kombinerat med lokal kunskap vara värdefull för att hitta effektivare avfallshanteringssystem. Innan man genomför ett skarp biogasprojekt är det klokt att göra en förstudie. Denna uppsats syftar till att genomföra en förstudie av biogassektorn i Rio de Janeiro, som uträttades med hjälp av ett multi-kriterieramverk. Ramverket består av fyra kategorier (potential, genomförbarhet, samt ekonomisk- och miljömässig prestanda), 14 nyckelområden samt 59 underfrågor. Ramverket användes för att assistera i insamlandet, strukturerandet och utvärderandet av information. En fältstudie på åtta veckor i Rio de Janeiro var en del av studien. Resultatet visar att ingen fullständig separering av organiskt avfall sker i Rio, vilket är orsaken till att studien inkluderar avfallsströmmarna blandat kommunalt avfall (som deponeras; benämns MSW) och delvis sorterat organiskt avfall (innehåller 85 % organiskt innehåll; benämns WHOC). Avloppsslam exkluderades från studien för att fokusera på fast kommunalt avfall. Potentialen och genomförbarheten är markant högre för MSW jämfört med WHOC, dock skall det understrykas att tillväxtpotentialen för WHOC är stor vilket ej framgår av siffrorna. Deponin mottager årligen nära 1.2 miljoner ton organiskt avfall (inkl. vatten) som ger en biogasutdelning på 140 miljoner Nm3 / år (50 – 55 % CH4); medan WHOC har en potential på 26 – 42 tusen ton (torrvikt) per år med en biogasutdelning på 6.6 – 19.5 miljoner Nm3 / år (55 – 63 % CH4). Genomförbarhetsanalysen för avfallsströmmarna visade att alla nyckelområden förutom ekonomiska instrument var värderade högre för MSW jämfört med WHOC. Studien visar vidare att det mest genomförbara användningsområdet för biogasen är injektion till gasnätet. Miljömässiga prestandan visar att substituering av naturgas med biogas kan sänka växthusgasutsläpp med 68 %, och för varje ton (torrvikt) av rötrester kan ca 8 kg fosfor och 36 kg kväve ersättas. Ekonomiska prestandan visar att biogasproduktion från deponi är mer kosteffektivt än i en bioreaktor, samt att ingen av biogaslösningarna är lönsamma, vilket kan väntas av en avfallshanteringslösning. Studien avslutas med att identifiera en rad utmaningar som biogassektorn i Rio ställs inför: en avsaknad på tillgång av biogas och ingen aktiv plan för att öka produktionen; ekonomiska utmaningar som indikerar ett behov av investeringsstöd; en brist på värdekedja för biogödsel. Resultatet av studien kan förhoppningsvis ge intressenter en bättre förståelse för vilka möjligheter och utmaningar som biogaslösningar ställs inför i Rio de Janeiro kommun – som i förlängningen kan öka möjligheterna för framgångsrika implementeringar av biogasprojekt i regionen.

MENVSC / Department of Ecology and Resource Management / Mining has historically been the mainstay of the South African economy and has both shaped its social and environmental fabric. However, it has left the country with a negative legacy of abandoned mines that present environmental problems, and public health and safety concerns. The common physical and environmental problems of most of these abandoned mines are associated with open shafts, unstable slopes of waste dumps and pits, and dilapidated mine infrastructure. Even though the problems of these abandoned mines are known, little has been done to rehabilitate these mines. Some attempts have been made to rehabilitate mine openings but efforts to rehabilitate features such as mine waste dumps and dilapidated infrastructure has been woefully inadequate. The reasons for ineffective rehabilitation measures may include inappropriate measures that are used in rehabilitation of the abandoned mines, lack of financial resources to carry out the rehabilitation and the need to prioritize abandoned mine features and mine sites for rehabilitation in view of the fact that there are many of these abandoned mines that require urgent attention and resources to rehabilitate them are limited. It is therefore important that practicable rehabilitation strategies are developed and used to rehabilitate mine features and sites to provide long-lasting solutions to the physical, environmental, and social problems. This study focused on the evaluation of strategies for rehabilitation of selected abandoned mine sites in the Giyani Greenstone Belt. The approach used in this study involved conducting a detailed field inventory and characterization to establish the nature and seriousness of the physical and environmental conditions of the selected abandoned/historic mining sites in Giyani Greenstone Belt. Field inventory and characterization involved traversing around the mine-site to locate and describe abandoned mine features. The Global Positioning System (GPS) was used in capturing the absolute location of the identified major abandoned mine features such as open mine shafts, tailings dump, and dilapidated infrastructure. Each of the identified mine features was critically analyzed by scoring and ranking the associated hazards. The scoring focused on the source of the hazard, exposure pathways, and possible damage that might be caused by the hazard. Analytical Hierarchy Process (AHP) and Pugh Matrix were used to devise a multi-criteria framework for evaluating mine site rehabilitation strategies. AHP method was utilized to evaluate the significance of the deciding factors and the Pugh Matrix to relatively compare the strategies for the selection of the appropriate rehabilitation options. The results of the study showed that the best approach to effectively address the physical and environmental hazards at Louis Moore and Klein Letaba abandoned mines of the Giyani Greenstone Belt was to give priority to extremely hazardous open mine shafts and tailings dumps. Mine shafts present a high risk of falling and drowning in water in the mine workings. Such risks are likely to lead to death with no hope of recovery of the body. The next mine features to be rehabilitated are the tailings dumps since they have relatively less physical hazards but extremely high environmental hazards. Abandoned mine infrastructure was found to be less hazardous and should, therefore, receive the least attention. The preferred rehabilitation strategies for abandoned mines features were evaluated after a comprehensive characterization of the site, this was done to ensure that the selected strategy addresses both physical and environmental problems identified on the site. Based on the results of evaluation, backfilling was selected to be the most suitable rehabilitation strategy for mine shafts as it has a very high potential to eliminate the risks of people falling into the mine shaft and the chances of water contamination by abandoned mine shafts. The most ideal rehabilitation option for tailings dumps was revegetation, since it ensures the safety of the site after implementation and minimizes the future environmental impacts such as the discharge of contaminants to the nearby environment. The most preferred rehabilitation strategy for dilapidated abandoned infrastructure in the study area was the demolition of the infrastructure, this strategy will improve the safety status of the mine sites and make the land they occupy available for other traditional post-mining land uses. It was concluded that the approach of prioritizing the extremely and moderately hazardous abandoned mine features is appropriate for use in developing countries where there are numerous abandoned mines and limited resources to rehabilitate them. This will go a long way in ensuring that characterization and rehabilitation of the abandoned mine features are effectively carried out within the constraints of resources. / NRF