LIFE CYCLE SUSTAINABILITY ASSESSMENT OF ELECTRICITY GENERATION FROM MUNICIPAL SOLID WASTE IN NIGERIA
Creators: name: Nubi, Oluwaseun Olukayode
Publisher: name: University of Surrey
Year: 2023

description: This thesis presents research conducted in a multidimensional Life Cycle Sustainability Assessment (LCSA) context to estimate and compare the environmental, economic, and social impacts of generating electricity from Municipal Solid Waste (MSW) in Nigeria. Two major cities Lagos and Abuja provide case studies to establish if their similarities or differences influence any of the LCSA impacts for the four WtE systems (Anaerobic Digestion, Incineration, Gasification, and Landfill Gas to Energy) examined. To address the research questions, the environmental, economic, and social sustainability has been assessed using the Life Cycle Assessment (LCA), Life Cycle Costing (LCC), and Social Life Cycle Assessment (sLCA) approaches, with the results integrated to evaluate the overall sustainability. <br>
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description: The LCA indicated that Anaerobic Digestion (AD) had the lowest environmental impacts amongst the four WtE systems for both cities based on all the impact categories except Photochemical Oxidation Potential (POCP). An analysis extension showed that diesel-based generators (DBGs) had the highest impact overall on a per kWh of electricity basis in Abiotic Depletion (fossil fuels) Potential (ADP)-14.1 MJ, Human Toxicity Potential (HTP) - 0.0732 Kg 1,4 DB eq, Acidification Potential (AP)- 0.0129 Kg SO2 eq and Eutrophication Potential (EP)-0.003 Kg PO4 eq and grid electricity the lowest impact in Global Warming Potential (over 100 years) (GWP)- 0.497 Kg CO2 eq, AP (0.0003 Kg SO2 eq) and EP (0.000061 Kg PO4 eq). The conclusion was that additional electricity supply from AD and its potential to reduce reliance on DBGs would be beneficial in environmental impact terms, especially regarding the GWP where that of AD for both cities (Abuja 0.507 Kg CO2 eq/kWh; Lagos 0.506 Kg CO2 eq/kWh) is lower than that of DBG. The LCC revealed that incineration was economically the most favourable option amongst the other WtE systems by having the lowest life cycle cost (LCC) for both cities (Abuja US$ 232.76/t; Lagos US$214.1/t). However, the economic assessment was also based on the levelized cost of energy (LCOE), net present value (NPV), internal rate of return (IRR) and payback period. The sLCA used a participatory approach to identify and assess 11 social impact subcategories, with “Improved Electricity Supply” and “Income”, respectively, having the most and the least significant social impacts associated with the potential WtE adoption in the two cities. Unlike the LCA and LCC, the sLCA did not identify the most socially favourable WtE system but generally showed a higher predicted social impact for WtE electricity generation in Lagos than in Abuja. This was attributed to the higher population, greater amounts of waste in Lagos, and its position as the country’s hub for many commercial and industrial activities, which have long been affected by inadequate electricity supply.<br>
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description: Overall, a ranking and scoring system and a multi-criteria decision analysis (MCDA) in form of multi-attribute value theory (MAVT) were used to combine the results of the three life cycle tools to evaluate the overall sustainability of this prospective use of WtE in Lagos and Abuja. Both approaches indicated that adopting WtE offered sustainability benefits for both cities, marginally more for Lagos than for Abuja. Given this, the LCSA methodology is beneficial for holistically considering and quantifying the wider life cycle impacts of systems across the span of the traditional dimensions of sustainability. As a decision support tool, LCSA can provide an overview of the sustainability performance of potential waste management and electricity generation systems used in Nigeria by highlighting aspects of WtE systems with significant negative or positive impacts so as to make improvements or exploit opportunities. To achieve the optimal benefit, decision-makers must consider the different trade-offs revealed by this type of analysis and the varying priorities of relevant stakeholders.<br>