Life cycle triple bottom line sustainability assessment of coal mine overburden sand versus river sand

Abstract

Crushed coal mine overburden (OB) waste rock has been found to be a promising, robust, and reliable alternative of river sand as fine aggregate in several construction applications. The processing of OB to application ready specification requires preprocessing that may cause negative environmental impacts. The environmental impacts have been quantified in previous studies. However, the economic and social impacts were not addressed, which has created confusion among practitioners and policy makers to take initiatives in promoting OB sand as a sustainable geomaterial considering the triple bottom line (environmental, economic, and social) approach. The present study uses Quantitative Assessment of Life Cycle Sustainability (QUALICS) framework that incorporates Analytical Hierarchy Process (AHP) and Integrated Value Model for Sustainable Assessment (MIVES) for integrated triple bottom line (environmental, economic, and social) assessment of processing of OB sand versus typical river sand. OB sand is found to cause relatively less impact in 6 out of 10 indicators in environmental assessment. High direct cost is neutralized by the monetized environmental benefit, direct benefits, and indirect benefits. The social score rating of OB sand is found to be relatively higher than river sand for all four criteria of social assessment (individual, community, socio-environmental, and socio-economic). The integrated sustainability indices for OB sand and river sand were determined to be 0.60 and 0.33, respectively, when equal weightage was given to all three triple bottom line aspects. These results clearly demonstrate that OB sand is a more sustainable option compared to river sand. Furthermore, conducting a sensitivity analysis with increased weightages assigned to the economic and social aspects reaffirmed that OB sand can be a sustainable replacement to river sand as fine aggregate.