China's dual-carbon narrative and bio-based flame-retardant supply chains: Industrial economics of phosphorylated recycled cellulose

This study examines the industrial economics of phosphorylated recycled cellulose flame retardants (PR-CFR) within China's dual-carbon policy framework, targeting peak carbon emissions by 2030 and carbon neutrality by 2060. Using a provincial panel dataset covering 28 Chinese provinces over 2008–2023, the study employs a Spatial Durbin Model (SDM), dynamic panel GMM, double-threshold panel regression, and mediation analysis to investigate how phosphorylation technology intensity, green procurement policy, and recycled cellulose feedstock availability jointly drive bio-based flame-retardant (bio-FR) industry total factor productivity (TFP), carbon footprint reduction, and downstream value chain integration. The principal results are fourfold. First, phosphorylation technology intensity exerts a direct effect of 0.312 and a spatial spillover effect of 0.168 on bio-FR industry TFP, confirming significant cross-provincial technology diffusion in the green chemical materials sector. Second, a double-threshold nonlinearity exists in the relationship between phosphorylation intensity and TFP: regime-specific coefficients are 0.102, 0.248, and 0.386 below, between, and above estimated thresholds of 0.35 and 0.70 on a normalized intensity scale, indicating that technology concentration above the upper threshold generates superadditive productivity returns. Third, carbon intensity reduction mediates 30.6 % of the total effect of the dual-carbon policy synergy index on bio-FR industry eco-efficiency, identifying decarbonization as the primary channel through which policy instruments translate into industrial competitiveness. Fourth, the Herfindahl-Hirschman Index for bio-based FR production has declined from 0.482 in 2008–0.171 in 2023, signaling a structural transition from monopolistic concentration toward competitive market organization as entry barriers fall with maturing phosphorylation technology. The findings advance the industrial economics of sustainable chemistry and offer policy guidance for accelerating China's bio-based flame retardant supply chain transition.