Integrating bio-based resource recovery and treatment into municipal solid waste management in developing countries: a focus on anaerobic digestion

Master Thesis


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University of Cape Town

Many authors, along with the United Nations Environment Programme (UNEP), argue that biological treatments such as anaerobic digestion (AD) and composting would be suitable in developing cities due the highly organic nature of their waste. AD entails the degradation of organic substances in the absence of oxygen, and its main products are CH 4-rich biogas and the remaining sludge. AD occurs in four main phases (hydrolysis, acidogenesis, acetogenesis and methanogenesis) and is a complex process, where microbiological, biochemical and physico-chemical phenomena are closely linked. Although composting the organic fraction of MSW (OFMSW) has been the preferred treatment method due to the low economic costs and operative ease, the production of biogas - a renewable energy source - has now positioned AD as the more energy efficient process as opposed to composting which requires energy inputs. A clear identification and understanding of the different organic waste streams available, their respective biogas potential, the engineering considerations and process limitations are needed to ensure good performance of AD plants. Location-specific data on the behaviour of different organic wastes in AD are, however, scarce, particularly in Africa. This dissertation is an attempt to generate Africa-relevant engineering knowledge through laboratory scale experiments of AD of organic waste streams typically disposed off in landfills. The main objectives of this dissertation are to (i) investigate the suitability for treatment by AD of typical organic waste streams in MSW, and (ii) consider the interplay between the nature of the available wastes and the temporal evolution of various process parameters. Finally, this dissertation aims to make sound recommendations from the data generated, building a preliminary source of knowledge for waste management officials and independent entrepreneurs.