Digital economy as a new engine for synergy of multi-pollutant mitigation: Evidence from a new perspective of marginal cost

Examining the impacts of digital economy (DE) on synergistic effect of pollution and carbon emission reduction (SERPCE) is essential for China's sustainable development and its dual carbon reduction goals. Current research focused on the impacts of DE on reducing individual pollutant, and ignoring the marginal costs of coordinated abatement efforts, which are crucial for balancing energy-environment-economy system. This study introduces a new SERPCE measurement method based on marginal abatement costs using parametric DDF functions with panel data from 30 Chinese provinces in 2011–2019. Findings indicate that DE is a new engine for reducing pollution reduction cost under joint mitigation policy, a 2.89% increase in SERPCE for each one-unit rise in DE, with energy consumption reduction and technological innovation as main transmission mechanisms. Positive effect of DE on SERPCE is with a threshold value 1778.3501, with the effect intensifying as the threshold is exceeded. Heterogeneity of effects emerges due to regional economic and resource differences, and substantial spatial spillover effects of DE on SERPCE emerges, indicating economic interconnectivity. This research provides a methodological framework for SERPCE quantification, enriching academic understanding of DE's impact on SERPCE and offering insights for policymakers in sustainable development strategies.