Application comparison and carbon emission accounting of different gas thermal desorption technologies

Through comparing the technical application and carbon emissions of in-situ and ex-situ gas thermal desorption technology in the remediation process of contaminated sites， the application trend of thermal desorption technology in future site remediation is comprehensively analyzed， and suggestions are provided for innovation and improvement of the technology under the requirements of green low-carbon remediation. The study showed that the amount of mechanical input in the ex-situ gas thermal desorption remediation process is higher than that of in-situ gas thermal desorption technology； however， the number of equipment input is lower than that of in-situ technology. The main energy consumption and carbon emission sources of this technology are gas， diesel， and electricity. According to the process data of four contaminated projects in China， the carbon emissions were calculated. The carbon emission per cubic contaminated soil repaired by thermal desorption technology was in the range of 170.74 to 373.25 kg CO2-eq. The carbon emissions of each cubic contaminated soil remediated by in-situ gas thermal desorption technology were lower than those of ex-situ gas thermal desorption technology. The proportions of carbon emissions of materials used in the remediation process for in-situ gas thermal desorption technology were in the order of natural gas>steel>concrete>electricity>NaOH>others； for the ex-situ gas thermal desorption technology， the order was natural gas>quicklime>concrete>electricity>diesel>others. To achieve the goal of green low-carbon restoration， pollution reduction， and carbon reduction， the following methods can be adopted： selecting the specific parameters of thermal desorption technology， optimizing the energy supply structure， upgrading or innovating the research and development of thermal desorption equipment， and combining thermal desorption technology with other technologies.