Techno - economic analysis of small scale waste to energy opportunities: A case study for Island Nations

Solid waste treatment methods including reuse and source reduction, recycling, composting, waste to energy and finally landfilling have been implemented in Organisation for Economic Cooperation and Development (OECD) countries. The first being the most preferred solution. In non OECD countries especially Small Islands Developing States (SIDs), customized solid waste treatment methods must be implemented. SIDS have unique characteristics such as dependence on foreign aid for investment, their heavy reliance on imported consumer goods and resources, their vulnerability to the effects of climate change and due to the lower amount of waste being generated, conventional solid waste management processes are not appropriate. Waste to energy can play a major role in treating waste in SIDS where land is scarce and where a diversification of the energy mix is crucial. The aim of this paper is to perform a techno - economic study to assess the smallest possible capacity of a waste to energy plant that is capable of treating municipal solid waste. An excel model was developed containing capital, operational and maintenance cost estimates. The economic performance of the model was assessed using the Net Present Value (NPV), Levelized Cost of Electricity (LCOE) and Simple Payback Period (SPP) tools. The Maldives were used as case study for developing a small scale plant. The model consists of a small scale prototype incinerator plant for energy extraction and an Organic Rankine Cycle (ORC) unit for electricity generation. The modelling gave the following results; an NPV of AUD$846,547, a SPP of 3.8 years and a LCOE of AUD$0.11/kWh for a plant capacity of 5,274 tpa, an ORC unit capacity of 235.20kW with an incinerator having a flow rate of 752.63kg/hr, gate fees of $50/t and a sale price of electricity of $0.35/kWh. The capital costs for the incinerator and the ORC unit were AUD$194,912.09 and $776,151.84 respectively. The biggest contributor to the capital expenditure was the flue gas treatment system with a total of AUD$ 814,156.04. Sensitivity analysis showed that the NPV was more sensitive to the price of electricity than to the gate fees.