Sanitary landfill is considered as a final repository of residual wastes. However, there is a need for volume reduction to increase the lifespan of the landfill and to stabilize these wastes to prevent environmental and health hazards. A possible option to achieve these objectives is a waste-to-energy (WtE) facility that can significantly reduce residual waste volume and generate electricity at the same time. In Metropolitan Manila, Philippines, there is no existing WtE facility for the treatment of residual wastes. In this study, the technical feasibility of a WtE plant for residual wastes from medical, industrial, and electronic sectors in the Metropolis is assessed.
A multi-attribute decision analysis method was used in the selection of the most appropriate waste conversion and power generation technology for residual waste. Seven waste conversion technologies were compared according to overall efficiency, waste reduction rate, maximum capacity, reliability, lifespan, energy conversion cost, and environmental emissions. Four power generation technologies were then ranked according to efficiency, cost, footprint, work ratio, emissions, and complexity. The pyrolysis-Brayton plant was found to be the most suitable WtE plant for the identified residual waste.
To determine WtE capacity, a waste analysis characterization study was conducted in wastes from health care facilities, manufacturing plants and treatment, storage and disposal facilities in Metropolitan Manila. Representative samples were obtained from these sectors to determine the generation rate and waste composition of residual wastes. Empirical, literature, and manufacturer’s data were used to calculate for product yield, energy requirement and energy yield for each sectoral waste. Based on the energy yield estimates, the WtE power plant was simulated at capacities of 1, 3, and 10 tons per day (tpd) for the three residual waste sectors.
The 10 tpd plant simulation for medical and industrial waste resulted to electricity generation of 800 kW and 1.2 MW, at efficiencies of 23% and 24%, respectively. The 3 tpd plant simulation for electronic waste generated 200 kW at 21% efficiency. The waste reduction rate obtained for medical, industrial, and electronic wastes was 84%, 90%, and 71%, respectively.
The results of the study showed that it is technically feasible to incorporate a WtE plant in the treatment and disposal of residual wastes in Metropolitan Manila. Furthermore, in consideration of the geographical attributes of the sectoral residual waste generators, the flexibility and small footprint of the pyrolysis-Brayton set-up is suitable. Installing 1–3 tpd plants in clustered locations will lessen transportation costs and land area requirement. Moreover, it is recommended that a financial feasibility study be done on the residual WtE plant, along with an enabling environment and business plan.