Developing a Circular Economy Framework for Organic Solid Waste Valorisation in Nigerian Megacities: Theory, Engineering, and Policy

This dissertation develops an original circular economy framework specifically designed for organic solid waste valorisation in Nigerian megacities, integrating environmental engineering analysis, economic modelling, and institutional design to produce a theory-grounded and operationally feasible approach to transforming urban organic waste from a disposal burden into a resource system. Nigerian megacities including Lagos, Kano, and Ibadan generate millions of tonnes of organic waste annually that is currently landfilled or informally dumped, representing a major environmental burden and a large untapped resource for composting, anaerobic digestion, and bio-based product generation. The theoretical contribution is a novel African Urban Organic Waste Circular Economy Framework that adapts European circular economy principles to the specific conditions of Nigerian cities, including the dominant role of informal waste sector actors, the structure of urban agriculture as an organic amendment market, and the regulatory and financial environment facing waste treatment investors. The framework is empirically grounded in a comprehensive characterisation of organic waste flows in Lagos undertaken through a material flow analysis encompassing households, markets, hotels, and food processing establishments. Life cycle assessment is applied to evaluate the environmental performance of six valorisation pathway scenarios including composting, black soldier fly bioconversion, biogas anaerobic digestion, and hybrid combinations. An institutional design analysis drawing on Ostrom's design principles for common resource governance is applied to identify the governance architecture required for collective organic waste management in informal settlements. Original contributions include the adapted African circular economy framework, the Lagos organic waste material flow dataset, and the comparative life cycle assessment results. Keywords: circular economy, organic waste, waste valorisation, Nigerian megacity, life cycle assessment.