Life cycle assessment comparison of thermal desorption and stabilization/solidification of mercury contaminated soil on agricultural land

Abstract

A life cycle assessment (LCA) was conducted to comprehensively evaluate and compare the cleanup methods of (1) thermal desorption and (2) soil stabilization/solidification (S/S) in addressing mercury contaminated soil on an agricultural land in southern China. It was estimated that conventional high temperature desorption results in 357 kg CO2-eq of greenhouse gas (GHG) emissions, while S/S with coal-based powdered activated carbon (PAC) results in 365 kg CO2-eq of GHG emissions per tonne of contaminated soil treated. Next, modifications were identified that reduced the life cycle GHG emissions for each method: an innovative acid-facilitated low temperature desorption method was estimated to reduce GHG emission to 264 kg of CO2-eq due to reduction in electricity usage. Additionally, S/S with biochar-based PAC reduces life cycle GHG emissions to 105 kg CO2-eq due to carbon sequestration during the pyrolysis of biomass. The LCA also identified critical contributing processes for each of these remedial alternatives, and suggested options to improve the net environmental benefit of remediation: using locally produced biochar-based PAC, using green cement, drying the soil in thermal treatment to reduce soil moisture content, using innovative methods to achieve low temperature desorption, using low emission fuel efficient trucks, and recycling waste heat in thermal treatment.