Environmental footprint analysis of remediation of contaminated soil based on chemical oxidation and ex-situ thermal pile desorption technology

Under the background of "Peak Carbon Dioxide Emissions" and "Carbon Neutrality", the technology type of China's soil remediation projects is continuously shifting towards low-carbon, low-energy, green and sustainable remediation technologies. The environmental footprint of remediation activities has been widely noticed and evaluated. SiteWise^TM, an environmental footprint assessment tool, was used to quantitatively assess the environmental footprint of the whole remediation process of a mercury and PAHs contaminated site in a steel plant in Chongqing. The results showed that the remediation of 3483 m³ of contaminated soil emitted a total of 990.52 t of greenhouse gases (GHGs), consumed 1.57×10⁷ MJ of energy and emitted 4.94×10³ kg of air pollutants. GHG emissions, energy consumption and air pollutant emissions at the construction preparation stage accounted for 6.0%-9.1% of the project, while those at the chemical oxidation stage accounted for 43.6%-48.1%. The GHG emissions, energy consumption and air pollutant emissions at the chemical oxidation + ex-situ thermal pile desorption stage accounted for 45.9%-47.5%. The chemical oxidation + ex-situ thermal pile desorption technology had a greater environmental impact compared to the chemical oxidation technology, and the environmental footprint for remediation of a single cubic volume of contaminated soil was about 5.28-5.97 times that of the chemical oxidation technology. The case study results showed that material consumption was the largest contributor to the environmental footprint, followed by equipment use, transport and residual handling.