Uncovering the Impact of the “Zero-waste City” Pilot Policy on Urban Green Innovation Efficiency

Addressing environmental challenges throughout urban development can spur green innovation. Despite its central role in solid-waste governance, the Zero-waste City initiative’s effects and mechanisms for urban green innovation remain unclear. This study quantifies the causal impact of China’s Zero-waste City pilot on urban green innovation efficiency (GIE). Using a panel of 252 prefecture-level cities (2012–2022), we construct a city-level GIE index via a super-efficiency slack-based measure (SBM) and designate the 11 first-batch pilots as the experimental group. From the remaining cities, we select 39 comparable controls using a propensity-score matching (PSM) model based on six pre-policy covariates, including GIE, economic development, foreign investment, population density, industrial structure, and urbanization. Policy effects are evaluated with a difference-in-differences (DID) model, complemented by six robustness checks. Mechanisms of policy-driven GIE promotion are further examined using patent application counts and the frequency of “Zero-waste City”-related terms in government work reports.