Valorisation of solid waste as key opportunity for green city development in the growing urban areas of the developing world

Abstract

Lack of integrated solid waste management practice in fast-growing cities of developing countries is posing a threat to sustainable and green cities development. The fast growing Jimma City in Ethiopia requires up-to-date waste quantification and characterization data for the planning and implementation of sound waste management options such as composting and energy recovery that could create new jobs and promote private sector involvement. Therefore, we quantified, characterized and evaluated energy potential and nutrient value of household solid waste from Jimma City. Total daily waste generated from the city’s households was estimated to be 85.8 tons, with an average per capita generation rate of 0.56 ± 0.17 kg/day. The biodegradable organic waste comprises 76% by weight and had optimum moisture content and carbon to nitrogen ratio for composting. The energy content of combustible household waste was estimated to be 17.5 MJ/kg for gross heating value and 9.54 MJ/kg for the net heating value that surpasses the lower limit for thermal treatment process to be economically viable. Waste-to-energy conversion of combustible waste of cities could reduce annually about 25,303 metric tons of carbon dioxide equivalent greenhouse gas emissions. Char briquettes produced through pyrolysis of solid waste could be a potential substitute for firewood to prevent deforestation and indoor air pollution. In conclusion, composting and pyrolysis are sound waste management options for green cities development in developing countries while minimizing public health risks and cost of treatment and disposal.