Key Takeaways & Executive Findings
- •• • Facility-based solidification/stabilization (S/S) exhibits a 12.00% higher carbon footprint (66.74 kgCO2e·m−3) compared to on-site S/S (59.59 kgCO2e·m−3), with total energy consumption 11.90% higher, primarily due to soil transport contributing 13% of emissions. • • Facility-based thermal desorption (TD) achieves an 11.10% lower carbon footprint (269.16 kgCO2e·m−3) than on-site TD (302.78 kgCO2e·m−3), with total energy consumption 3.97% lower, attributed to landfill biogas utilization for heat and power, reducing emissions by 314.65 tCO2e and 115.86 tCO2e, respectively. • • Reagent production dominates GHG emissions in S/S processes, contributing 77%–86%, while heat supply dominates in TD processes, contributing 70%–72%, identifying critical emission reduction levers. • • Sensitivity analysis shows that even with one-way transport distances varying from 15 to 65 km, facility-based TD maintains a lower carbon footprint than on-site TD, demonstrating robust low-carbon advantages.
Abstract
To evaluate the carbon footprint differences between the emerging ex-situ remediation facility mode and the conventional on-site remediation mode in China, this study employed the SEFA tool to calculate greenhouse gas (GHG) emissions and energy consumption for four typical remediation scenarios. Results indicate that the carbon emission intensity of solidification/stabilization (S/S) in the remediation facility is 12.00% higher than that of on-site S/S, with unit carbon intensities of 66.74 and 59.59 kgCO2e·m−3, respectively, and total energy consumption 11.90% higher. The soil transport segment in the facility S/S contributes 13% of carbon emissions, being the primary reason for its higher total carbon footprint. Conversely, thermal desorption (TD) in the facility exhibits 11.10% lower carbon emissions than on-site TD, with unit intensities of 269.16 and 302.78 kgCO2e·m−3, and total energy consumption 3.97% lower, mainly due to the utilization of landfill biogas as renewable energy for heat and power generation, while soil transport contributes only 3% of emissions. The reagent segment in S/S and the heat supply segment in TD account for 77%–86% and 70%–72% of total GHG emissions, respectively. The study demonstrates that remediation facilities, leveraging advantages such as landfill biogas, can actively aggregate contaminated soil from surrounding areas for centralized thermal desorption, which is beneficial for regional carbon emission reduction in soil remediation.
1. Introduction
The remediation of contaminated soil is increasingly constrained by carbon emission reduction targets under China's dual-carbon strategy. Conventional on-site remediation modes, while widely adopted, often rely on energy-intensive processes and fragmented management, leading to higher per-unit carbon footprints and operational inefficiencies. The emergence of centralized ex-situ remediation facilities offers potential economies of scale and centralized pollution control, yet their environmental footprint, particularly carbon emissions, remains poorly quantified compared to traditional on-site approaches.
This study addresses this gap by applying the SEFA (Spreadsheets for Environmental Footprint Analysis) tool to systematically compare four remediation scenarios: on-site versus facility-based solidification/stabilization and thermal desorption. By quantifying GHG emissions and energy consumption across the full remediation chain—including excavation, transport, treatment, and disposal—this research provides empirical evidence on whether the transport burden of ex-situ modes negates their potential benefits. The findings reveal that while facility-based S/S incurs higher emissions due to transport, facility-based thermal desorption achieves significant carbon savings through renewable energy integration, offering a data-driven basis for optimizing remediation strategies in the context of green and low-carbon transitions.
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LI De'an, DENG Yirong, LI Fuhan, ZHANG Zhenxing, LI Shuo, WANG Jun (2026). Comparative Carbon Footprint of Ex-situ Remediation Facility and On-site Remediation Modes for Contaminated Soil. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202511046
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Frequently Asked Questions
What are the primary drivers of the higher carbon footprint in facility-based solidification/stabilization compared to on-site S/S?
The higher carbon footprint (12.00% increase) is primarily attributed to soil transport, which contributes 13% of total emissions in the facility mode, whereas on-site S/S avoids long-distance transport. The unit carbon intensities are 66.74 kgCO2e·m−3 for facility S/S versus 59.59 kgCO2e·m−3 for on-site S/S.
How does the use of landfill biogas in the remediation facility affect thermal desorption carbon emissions?
Landfill biogas provides renewable heat and electricity, reducing carbon emissions by 314.65 tCO2e for heat supply and 115.86 tCO2e for electricity compared to natural gas and grid electricity, respectively. This leads to an overall 11.10% lower carbon footprint for facility-based thermal desorption (269.16 kgCO2e·m−3) versus on-site (302.78 kgCO2e·m−3).
What is the sensitivity of the carbon footprint advantage of facility-based thermal desorption to transport distance?
Sensitivity analysis shows that even when one-way transport distances vary from 15 to 65 km, facility-based thermal desorption maintains a lower carbon footprint than on-site thermal desorption, indicating a robust advantage under typical regional logistics conditions.
Which process segments contribute most to GHG emissions in solidification/stabilization and thermal desorption?
In solidification/stabilization, reagent production accounts for 77%–86% of GHG emissions, making it the dominant contributor. In thermal desorption, heat supply contributes 70%–72%, while electricity use contributes 14%–16%, highlighting the importance of optimizing these energy-intensive inputs.
What are the broader environmental and operational benefits of the remediation facility mode beyond carbon reduction?
Beyond carbon reduction, the facility mode offers enhanced secondary pollution control, centralized supervision, and improved remediation effectiveness due to permanent infrastructure. It also accelerates land redevelopment by enabling timely transfer of contaminated soil, thereby supporting synergistic pollution reduction and carbon mitigation.
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