How can the Largest Landfill in China be Transformed into an Ecological Green Land?
In late December 2022, the ecological restoration project of Chongqing Changshengqiao Landfill was fully completed. What was once China’s largest landfill occupying approximately 69 hectares has been transformed into an ecological green land with beautiful scenery and fresh air. The project has achieved the restoration and reuse of urban land, providing a replicable model for urban ecological rehabilitation and functional recovery.
Pic 1. The Ecological Restoration Project of Chongqing Changshengqiao Landfill
The landfill primarily served as the major disposal site for domestic waste from five main districts in Chongqing. Commissioned in July 2003, it reached a peak daily processing capacity of approximately 3,000 metric tons of waste. By its shutdown in May 2016, the landfill facility had cumulatively treated over 10 million tons of domestic waste.
As Chongqing’s urban expansion progressively extended the municipal boundaries, the landfill’s environmental impacts - including groundwater contamination and odorous gas - began significantly affecting surrounding communities. This necessitated immediate remediation measures to guarantee residences’ public health.
In April 2018, the Chongqingqiao project was officially implemented, with the development philosophy of ecological rehabilitation and urban restoration. The project implemented two key mitigation measures: constructing leachate treatment and hazardous gas processing plants along the perimeter to minimize pollution impacts, while simultaneously developing an ecological theme park to improve ambient air, groundwater and soil quality. These dual interventions enabled sustainable urban land recycling, effectively enhancing the city’s developmental potential and elevating residents’ happiness through environmental revitalization.
Pic 2. The Greened Landfill
To mitigate the safety risks posed by toxic gases (including methane, carbon monoxide, and hydrogen sulfide) generated during waste decomposition, the project construction team formulated a targeted Environmental Protection Work Plan and established a dedicated Environmental Control Unit to institutionally integrate ecological conservation with operational safety. The project implemented dual safety guarantees: (1) providing workers with positive-pressure respirators and gas masks, and (2) installing intelligent monitoring systems for real-time tracking of worksite conditions and hazardous gas concentrations. This enabled dynamic risk alerts and data-driven optimization of construction philosophy, ensuring uninterrupted progress while maintaining strict air quality compliance.
Pic 3. Landfill Leachate Treatment Area
To prevent landfill leachate from constraining the construction progress, the project team established a technical problem-solving group. Following on-site investigations and scientific feasibility studies, they implemented a prioritized construction scheme featuring leachate collection blind drains. This system channels concentrated leachate to either treatment stations or temporary regulating tanks for filtration, ensuring both operational efficiency and environmental compliance throughout the construction phase while minimizing secondary pollution.
Due to the complex composition, large volume, and varying moisture content of sludge in different areas of the landfill, the constructor conducted abundant research and experiments to develop corresponding solidification ratios tailored to sludge with different water contents. This ratio significantly improved the efficiency and quality of sludge solidification construction at the landfill, saving both time and material costs. Based on this achievement, the project developed a “Sludge Solidification Spraying Device for Landfills,” which was granted a national utility patent.
To address challenges including unstable waste composition, high concentrations of combustible toxic gases, and difficult gas collection, they implemented technical innovations through comparative research, theoretical analysis, and simulation testing. This led to the development of an in-situ solidification remediation solution coupled with a construction technique primarily employing full-casing follow-up rotary drilling for gas venting stone cage wells. The approach effectively minimizes secondary pollution from escaping hazardous, toxic, and flammable gases while significantly enhancing worksite safety during remediation.
Through a series of innovative processes and methodologies, the project team successfully completed landfill shaping, landfill gas collection/treatment/utilization, and initial greening with exceptional efficiency and quality. The overwhelmed landfill has truly achieved its remediation goal of "turning waste into wealth." The project culminated in the development of the "Comprehensive Ecological Remediation Technology for Large-Scale Operational Urban Landfills," which provides a replicable state-owned-enterprise model for advancing ecological restoration nationwide, earning widespread recognition across society.
