Strategies to improve anaerobic digestion and environ-economic analysis of municipal solid wastes management options

A Thesis Submitted in Fulfilment of the Requirements for the Degree of Doctor of Philosophy in Environmental Sciences and Engineering of the Nelson Mandela African Institution of Science and TechnologyDifferent strategies have widely been applied for improving the anaerobic digestion of the organic fraction of municipal solid wastes. However, because of the heterogeneous compositions of organic fraction of municipal solid wastes, studies on different strategies are still required. This thesis focused on examining methods to improve anaerobic digestion of organic fraction of municipal solid wastes and environ-economic analysis of municipal solid wastes management options. Firstly, the study examined the effects of fungal (Pleurotus ostreatus) treatment of the banana leaves wastes towards edible mushrooms and biogas recovery. Secondly, the study assessed the effectiveness of banana winery wastewater in digesting the banana leaves wastes to improve methane yield. Thirdly, the study examined the potential of edible clay soils towards improving the anaerobic digestion of food wastes for biogas recovery. Next, the study analyzed and compared the environmental impacts of anaerobic digestion and other municipal solid waste management scenarios in the Arusha City of Tanzania. Finally, the study assessed the economic feasibility of the biogas plants for treating food and banana leaves wastes in the Arusha City of Tanzania. All the anaerobic digestion experiments were carried out in batch reactors. The environmental impact was analyzed using a life cycle analysis methodology. Fungal treatment of banana leaves wastes prior to anaerobic digestion process resulted in the biogas yield of 282 mL g -1 VS -1 and production of 181 ± 19 g of edible mushrooms per 2 kg of banana leaves wastes. The cost analysis revealed that mushroom cultivation has a higher economic value and therefore favoured before the anaerobic digestion process. Banana winery wastewater pre-treatment of banana leaves waste resulted in increased methane yield by 193% compared to non-pretreated banana leaves waste. The edible clay soils supplementation in the anaerobic digestion process resulted in an increase of 26.9% methane yield in a reactor with edible clay soils supplementation. Evaluations on environmental impacts revealed that the anaerobic digestion process outranked the current management option (Landfill) with the least environmental burdens. The study also revealed it is economically viable to invests the biogas plants for treating food and banana leaves wastes in Arusha City of Tanzania