Life cycle assessment of using calcium carbonate in waste flooring for neutralization of acid mine drainage: A comparison study

Acid mine drainage (AMD) poses a major environmental pollution issue linked to historical mining sites, frequently necessitating remediation approaches that utilize neutralizing agents. A life cycle assessment (LCA) was performed to analyze the environmental effects of traditional remediation methods compared to the use of downcycled carpet tile waste at a theoretical AMD site. Polyolefin-based carpet tiles can incorporate more than 65% finely ground calcium carbonate (CaCO 3 ) powder by weight in their compound-blended and extruded backing, presenting a potential novel approach for neutralization by repurposing a complex and abundant material that is difficult to recycle. Six scenarios were examined per the functional unit of one cubic meter of AMD water that consider various remediation construction materials (concrete and plastic liner) and neutralization methods (downcycled carpet tiles and limestone). Three key midpoint impact categories were analyzed: global warming potential (GWP), particulate matter formation potential (PMFP), and total human toxicity potential (HTP), which collectively represented 94% of the endpoint outcomes. Midpoint results showed that the limestone neutralization that used a plastic lined system had the lowest GWP (1.21E-02 kg CO2 eq), PMFP (5.46E-05 kg PM 2.5 eq), and total HTP (3.41E-03 kg 1,4-DCB) per cubic meter of AMD water. On the contrary, the system that used downcycled carpet tile waste in a reinforced concrete tank had the highest 480% higher GWP, 350% higher PMFP, and a 428% higher total HTP. Although this downcycling method may yield higher emissions, it helps extend the lifespan of carpet tiles and reduces the need for additional mining operations. • Life cycle assessment evaluated multiple acid mine drainage remediation methods • Downcycled carpet tiles and traditional limestone neutralizers were compared • Three key impact categories represented 94% of endpoint outcomes (GWP, PMFP, HTP) • Downcycling scenarios often yielded higher emissions yet reduces further mining • Omitting transportation makes the downcycled carpet scenarios more favorable