Metal waste in municipal solid waste incineration bottom ash: characterization, source identification, and recovery potential

Abstract The steady reduction in landfill capacity and limited land area for constructing new landfills require the recycling of municipal solid waste incineration bottom ash (MSWIBA). While most studies focus on using MSWIBA powder as a construction material, few have addressed metal waste characterization and recovery. This study quantified magnetic metal waste (MW) and nonmagnetic metal waste (NMW), which account for 14.40 ± 4.02 and 0.57 ± 0.20 wt% of MSWIBA, respectively. The identification of original discarded products, combined with elemental analysis, shows that the top 10 MW categories represent over 90% of the total MW weight, and most identifiable MW originated from daily necessities and common metal fittings. Notably, 16.50% of disposed metal waste, which should have been collected through separate collection systems, was found in MSWIBA. Some MW categories contained relatively high Cu, which could affect regenerated steel quality, while trace elements such as Cr, Mn, Co, Ni, As, and Mo were enriched in the magnetic ferrous powder. The estimated amounts of Ni and Co contained in MW landfilled annually correspond to 10.96% and 6.27% of Japan’s domestic demand. These findings indicate a significant recovery potential and call for improvements in upstream waste separation and downstream mechanical separation.