Co-pyrolysis of sea rice straw and low-density polypropylene: Implications for advancing sustainable fuel production

Co-pyrolysis of sea rice straw (SR) and low-density polypropylene (LDPP) was systematically investigated to address challenges in valorizing high-ash, high-silicon agricultural residues and plastic waste. Optimal conditions (500 °C, 80 mL/min N₂, SR:LDPP=1:3) synergistically enhanced oil yield by 257.6 % relative to SR pyrolysis alone while drastically improving fuel quality. Comprehensive characterization revealed a 92.8 % reduction in oxygenated compounds and 93.8 % nitrogen reduction, elevating calorific value by 70.3 % to 42.62 MJ/kg. Thermal and spectroscopic analyses (TG-FTIR/GC-MS) demonstrated hydrogen radical transfer from LDPP decomposition as the core mechanism, facilitating deoxygenation through CO/CO₂ formation and hydrocarbon enrichment. This process effectively mitigated SR's inherent limitations—low oil yield and poor stability—while converting waste plastic into valuable hydrogen donors. The study establishes a synergistic route for transforming challenging coastal biomass and plastic pollution into premium bio-oil, achieving 82.2 % carbon content and near-complete nitrogen removal (0.04 wt%). These findings provide critical insights for sustainable waste management in saline agriculture regions, advancing circular economy strategies for problematic feedstocks.