Decentralized-to-Centralized Transition of Yibin’s Camphora longepaniculata Essential Oil Processing Industry: A Scenario-Based LEAP Case Study of Energy and Pollution–Carbon Co-Benefits

Traditional household-based decentralized agro-processing is an important source of air pollution in rural China, yet the pollution–carbon co-benefits of centralization remain poorly quantified. In this paper, a LEAP-based scenario framework (2018–2035) is developed for Yibin’s Camphora longepaniculata essential oil processing industry under four scenarios: baseline, policy (27% centralization share), enhanced scenario 1 (ENH1; 50% centralization share), and enhanced scenario 2 (ENH2; 50% centralization share with a 2% efficiency retrofit). The framework simulates energy demand and emissions of CO2, PM10, SO2, NOx, and VOCs based on specified emission factors and technological assumptions. The results indicate that centralization reduces unit energy consumption by 51.20% and CO2 intensity by 63.12%. The 27% penetration rate (current policy) lowers emission levels but cannot alter the growth trajectory during output expansion, whereas the 50% penetration rate achieves net CO2 and energy reductions of 31.56% and 25.60%, respectively, relative to the baseline. All pollutants exhibit synergy elasticity coefficients (ε) above unity (PM10 > SO2 > VOCs > NOx); these coefficients are governed by the emission factor structure rather than the penetration rate. Thus, scaling centralization drives absolute reductions, whereas co-benefit enhancement requires process or end-of-pipe upgrades. All of the reported results are scenario-based model outputs, not field measurements, and biogenic CO2 is included only for cross-scenario comparability, not as a climate impact claim.