Hengshui’s “zero-waste city” initiative demonstrates synergistic pollution reduction and climate action through agricultural waste innovation

The full paper, titled Ecological Circular Disposal of Agricultural Waste: Integrated Production of Gas, Electricity, Heat, and Fertilizer for Achieving Synergistic Effects of Pollution Reduction and Carbon Emission Reduction, was published on March 18, 2025, in Circular Economy.

Key Innovations and Findings

The study focuses on Hengshui City, a national pilot for China’s “zero-waste city” initiative, which generates 4 million tons of livestock manure annually. By carrying out the construction of the “zero- waste city”, improving the technical system, institutional system, and market system for solid waste from agricultural sources, and adopting advanced anaerobic digestion technology, the city has established a circular model that integrates biogas production, electricity generation, heat recovery, and organic fertilizer manufacturing. Key outcomes include:

1. Annual GHG Reduction: The project of combined production of gas, electricity, heat and fertilizer in Anping County, Hengshui City reduces the local greenhouse gas emissions by 87,208.5 tons of carbon dioxide equivalent every year. This is mainly achieved by carrying out the resource utilization of manure, reducing the methane emissions from manure management and replacing the use of fossil fuels.
2. Economic Growth: Since 2020, driven by the construction of Hengshui’s “zero-waste city”, the utilization rate of agricultural waste has increased to over 90%. The regional gross domestic product has increased by 21%, and the fixed-asset investment in agriculture, forestry, animal husbandry, and fishery has increased by more than 15%.
3. Policy Synergy: The “1+N+13” institutional framework for the construction of the “zero-waste city” has been established. By combining centralized planning with localized solutions, it has promoted sustainable biogas projects and cross-sectoral cooperation.

Dr. Wang Zhihua from the Research Institute for Environmental Innovation (Suzhou), Tsinghua, who is also the first author of this article, said that this study tried to conduct a reduction in pollution and carbon emissions analysis of the Hengshui “zero-waste city” construction based on the DPSIR model from 2020 to 2023. Under the background of “zero-waste city” Construction in China, the case study is very essential for understanding the details and major implication of the policy. It can provide some useful information for effective management of livestock and poultry manure waste.

Methodology and Analysis

In this study, based on the “driving force-pressure-state-impact-response” (DPSIR) model, an analysis of pollution and carbon emission reduction in the construction of Hengshui’s “zero-waste city” was carried out. From the three dimensions of economy, environment and society, 19 indicators were selected for evaluation. Moreover, the entropy weight-technique for order preference by similarity to an ideal solution (TOPSIS) method was used to standardize the data from 2020 to 2023, quantifying the impacts of factors such as the growth of gross domestic product (GDP), the scale of livestock farming, and the growth rate of fixed asset investment in agriculture, forestry, animal husbandry and fishery. In addition, the study adopted the approved Clean Development Mechanism (CDM) method (AMS.Ⅲ.D.ver.21) to analyze the greenhouse gas emission reduction effect of the comprehensive biogas utilization project in Anping County, Hengshui City. The results show that:

(1) Core Drivers: The driving factors for pollution and carbon emission reduction in the agricultural sector during the construction of Hengshui’s “zero-waste city” mainly include economic and social development, the employment situation of residents, as well as social response factors such as fixed asset investment in agriculture and the construction of standardized and large-scale breeding and livestock facilities. A large amount of agricultural waste in Hengshui and the environmental governance pressure brought about by air pollution control seriously restrict the work of pollution and carbon emission reduction in the construction of Hengshui’s “zero-waste city”.

(2) Emission Hotspots: The implementation of the project of co-production of “gas, electricity, heat and fertilizer” can effectively reduce greenhouse gas emissions by 87,208.5 tons of carbon dioxide equivalent per year, with a reduction rate of over 64%. The emission reduction amount of this model is significantly affected by three factors: biogas leakage, emissions during the storage of livestock and poultry manure, and emissions generated during equipment operation. Among them, the emissions during the storage of livestock and poultry manure have the greatest impact on the emission reduction amount, accounting for 59% of the emissions after the implementation of the biogas project.

(3) Comprehensive Efficiency: Using the technique for order preference by similarity to an ideal solution (TOPSIS) method, the comprehensive evaluation index of pollution and carbon emission reduction in the agricultural sector during the construction of Hengshui’s “zero-waste city” from 2020 to 2023 was calculated. The results show that the comprehensive evaluation index of pollution and carbon emission reduction in the agricultural sector during the construction of Hengshui’s “zero-waste city” has been increasing year by year from 2020 to 2023, with an 87% growth in 2023 compared to 2020. This indicates that remarkable achievements have been made in pollution and carbon emission reduction during the construction of Hengshui’s “zero-waste city”

Challenges and Global Implications

While the model succeeds in reducing emissions, challenges persist. Dr. Lyu Pu, the corresponding author of the paper and an environmental policy expert, pointed out that, “Nutrient runoff from biogas-derived fertilizers risks eutrophication if mismanaged. Precision application and monitoring are critical.”

This study emphasizes the role that the circular economy plays in achieving the United Nations’ sustainable development goals. Through the ecological circular model of combined production of gas, electricity, heat, and fertilizer, Hengshui has created green jobs. It has reduced the use of chemicals by replacing synthetic fertilizers with organic ones, and has decreased the use of fossil energy by incorporating biomethane into the natural gas network.

Globally, the findings align with circular economy strategies in the EU, Japan, and Singapore. For instance, Surrey, Canada, uses similar anaerobic digesters to power municipal fleets, while Thailand’s “3Rs” policy (reduce, reuse, recycle) mirrors Hengshui’s approach.

About Circular Economy

Circular Economy (CE) is an international fully open-access journal co-published by Tsinghua University Press and Elsevier and academically supported by the School of Environment, Tsinghua University. It serves as a sharing and communication platform for novel contributions and outcomes on innovative techniques, systematic analysis, and policy tools of global, regional, national, local, and industrial park's waste management system to improve the reduce, reuse, recycle, and disposal of waste in a sustainable way. It has been indexed by Ei Compendex, Scopus, Inspec, CAS, and DOAJ. At its discretion, Tsinghua University Press will pay the Open Access Fee for all published papers from 2022 to 2026.