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

The comprehensive utilization of agricultural solids is a critical element in building a “Zero Waste City” and a vital measure for promoting the green and low-carbon development of agriculture and rural areas. Since the launch of the “Zero Waste City” initiative in Hengshui, China, the city has continuously promoted waste reduction at the source and resource utilization. Business models and institutional mechanisms for the utilization of various types of solid waste have been actively explored, and a model for reducing pollution and carbon emissions through the production of “gas, electricity, heat, and fertilizer” in the agricultural sector has been established. In this study, an analysis of pollution and carbon emission reduction in the Hengshui “Zero Waste City” construction is conducted on the basis of the “driving force–pressure–state–impact–response” (DPSIR) model, and the entropy weight-TOPSIS method is used to standardize the data from 2020 to 2023. In addition, this study uses the approved clean development mechanism (CDM) method (AMS.Ⅲ.D.ver.21) to analyze the greenhouse gas emission reduction effect of the comprehensive biogas project in Anping County, Hengshui City. The results revealed that the reduction in pollution and carbon emissions of the Hengshui “Zero Waste City” construction from 2020 to 2023 was significant. The core factor affecting the “Zero Waste City” construction in Hengshui is the development of social and economic activities; the increase in fixed asset investment in agriculture, forestry, animal husbandry, and fisheries; the improvement in residents’ income; and the increase in the employment rate. Hengshui has driven the construction of a “Zero Waste City” through industrial development, forming a comprehensive utilization model of livestock manure that combines the production of gas, electricity, heat, and fertilizer. This is in line with the demand for the construction of a “Zero Waste City” in Hengshui. Moreover, the case project can reduce greenhouse gas emissions by 87,208.5 tons of CO₂ equivalent per year, with a reduction rate of over 64%.