Life cycle assessment of reusing fly ash from municipal solid waste incineration

Many countries consider the fly ash produced from the incineration of municipal solid waste (MSW) as hazardous waste. In Taiwan, 24.5 thousand tons of MSW is incinerated and 554.7 tons of fly ash is produced daily. As landfill capacity in the country is limited, this vast amount of fly ash should ideally be reused. However, some treatment methods to enable the reuse of fly ash can have a worse impact on the environment than was previously believed. The aim of this research was therefore to compare the different processes for the reuse of fly ash by employing data collected from the incineration process in Taiwan in order to establish a life-cycle assessment (LCA) database. The database, containing information on the assessment of reuse treatments, is intended to inform decision making on the best practices for the reuse of fly ash. The study poses four scenarios for reuse treatment and disposal of one ton of fly ash: 1) landfilling after solidification, 2) reuse as cement after a washing process, 3) reuse as bricks after a washing process, 4) reuse as an alkali in the waelz process of steelmaking. The results from the LCA showed that the washing processes consumed more water but less electricity; however, more electricity was consumed and higher toxicity was caused in scenario 4, the reuse as an alkali in the waelz process. More water and chemical additives were used in scenario 2 because of the higher limits of chloride compounds and heavy metals used in construction materials. To conclude, the comprehensive LCA inventory database established by this study could assist in reducing the environmental impacts of reuse treatments for fly ash, and consequently could contribute to the safer management of fly ash worldwide. (C) 2015 The Authors. Published by Elsevier Ltd.