Physicochemical characteristics of bottom ash from waste-to-energy incineration pilot plant in Indonesia

Abstract

Municipal solid waste (MSW) disposal has emerged as a major concern in large cities across Indonesia. Waste-to-energy (WtE) incineration is an attractive method that can significantly reduce volume of waste; however it generates residues, namely bottom ash and fly ash. This study presents the characteristics of bottom ash from the MSW WtE incineration pilot plant in Indonesia. The physicochemical characterization of bottom ash was determined X-ray fluorescence (XRF) and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS). The results showed that CaO (46.80%) was the major component, followed by SiO2 (12.30%), Al2O3 (8.80%), and Fe2O3 (8.20%). SEM images showed that the surface morphology of bottom ash appeared flaky, rod-like, and irregular shape. Inert materials, like iron scrap, glass, ceramic, and stone, accounted for 16.7% of the total dry weight of bottom ash. Toxicity characteristic leaching procedure (TCLP) test of 11 heavy metals in bottom ash was carried out, and all of them were detected at very low concentration, indicating that bottom ash possessed a low risk level to human health and environment. This study provides important information on the characteristics of bottom ash from MSW WtE incineration in Indonesia that would be useful in facilitating management and disposal of bottom ash.