Synergistic efficiency in greenhouse gas emission reduction and water pollution control: evaluating policy impacts in China

Abstract

The synergistic reduction of wastewater greenhouse gases (GHGs) and pollutants presents a critical environmental challenge. Understanding the synergistic efficiency and the factors that influence it is crucial for informed policy-making, but methods for assessing this efficiency are currently lacking. This study evaluates the synergistic efficiency in China from 2009 to 2019 using the elastic coefficient method, and assesses strict water policy impacts using double machine learning (DML). Results indicate that before 2015, China experiences synergistic increases, which shift to non-synergistic following the implementation of a strict water policy in 2015. Despite improved wastewater treatment rates, this policy paradoxically increases GHG emission intensity, leading to a “water-carbon” contradiction, especially in water-scarce, poorly enforced, and underdeveloped regions. The policy effect on GHG emission intensity is most influenced by wastewater pipeline infrastructure, followed by socioeconomic development, technological innovation, and industrial structure. Inefficiencies in GHG emission reductions are due to expanded wastewater treatment facilities and lower industrial energy efficiency. Conversely, higher salaries and technological advancements facilitate emission reductions. To achieve the synergy of effluent pollution and GHG reduction in the wastewater sector, provincial control priorities into four patterns are explored. This study provides guidance for low-carbon retrofitting of existing wastewater treatment plants and informs the design of effective water policies.

Graphical abstract

Keywords

Wastewater greenhouse gas / “Water-carbon” contradiction / Synergistic efficiency / Policy effect / Double machine learning

Highlight

	● Developed a method to assess synergistic efficiency and its spatiotemporal changes.
	● We use double machine learning to study the wastewater policy effect.
	● Water-carbon contradiction varies across regions, water resources, and economy.
	● We analyze pathways based on wastewater treatment plants, energy use, and salaries.

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