The impacts of furnace and fuel types on the hazardous heavy metal contents and leaching behavior of woody biomass fly ash

In efforts to reduce net CO 2 emissions, the use of woody biomass as a fuel for power generation has grown rapidly. However, this practice is expected to generate large amounts of combustion ash. To support the subsequent use and disposal of combustion ash, it is important to understand its hazardous heavy metal (HHM) contents and leaching behavior. Therefore, we investigated the impacts of furnace type and fuel on HHM contents and leaching behavior based on 60 types of woody biomass fly ash (WBFA). A safety assessment of WBFA as fertilizer based on HHM contents revealed that 20% of the WBFA samples exceeded the prescribed standards. Therefore, WBFA would require preprocessing before reuse as fertilizer. The leaching test results showed that 95% of the WBFA samples could be landfilled as industrial waste without special treatment. However, prior to reuse in construction materials or soil amendments, it would be necessary to remove or fix HHMs to prevent leaching. Overall, WBFA generated from the combustion of waste wood as fuel tended to have higher HHM contents and leachate concentrations than WBFA from other woody biomass-based fuel types.