Life cycle assessment of artificial sintered flyash lightweight aggregate produced in India using OFF gas and coal based thermal power

Abstract

The potential environmental impacts associated with production of sintered flyash lightweight aggregate (SFA) needs comparison with natural aggregates (NA) which can directly help in the selection of sustainable materials. In the previously reported research, the impact of SFA manufacturing using off gas as thermal energy source is not assessed and site-specific data is also not available. Therefore, this study covers the life cycle assessment (LCA) of SFA production in India using coal based thermal power and off gas as source of thermal energy. In the present LCA study, all the inputs like raw materials, heat, electricity and outputs like product and emissions associated with production of SFA were inventoried, to evaluate the life cycle environmental impacts of SFA. The main purpose of this LCA study is to evaluate the alternative scenarios of making the SFA environment friendly by use of renewable energy and green fuels. Within the SFA manufacturing plant, a number of discrete unit processes were identified like raw material handling & mixing, palletization, sintering and screening and input–output analysis is undertaken for each unit process (including electricity and transportation). The impacts associated with SFA are compared with NA in terms of Global Warming Potential, Acidification Potential, Eutrophication Potential and Abiotic Depletion Potential. In this study, it was found that the environmental impacts associated with production of SFA are 55 to 90% higher as compared to NA. The Global Warming Potential impacts associated with 1 tonne of SFA are 83% higher as compared to 1.5 tonne of NA. Similarly, in terms of acidification potential and eutrophication potential, SFA are having 55% and 90% higher impacts as compared to natural aggregate respectively. The three alternative scenarios are developed based on contribution analysis. The alternative scenarios evaluated in this study are (a) electricity consumption based on 100% Solar power (b) biomass based OFF gas and electricity from coal based thermal power plant and (c) biomass based OFF gas and electricity from Grid. The study concludes that heat consumption in sintering process and electricity consumption in various unit processes are the main contributors for various environmental impacts in production process of SFA. The alternative routes like usage of biomass based OFF gas and grid-based electricity will help in reduction of environmental impacts associated with production of SFA and make it comparable with natural aggregates.