Synergistic Valorization of Biomass and Plastic Waste: Catalytic Co-Pyrolysis for Premium Hydrocarbon-Rich Bio-Oil

The twin environmental crises of proliferating lignocellulosic waste and persistent plastic pollution demand integrated, circular solutions. This study presents a novel and transformative approach by synergistically co-pyrolyzing Prosopis juliflora wood (PJ-WB) with polyolefin (PO) plastic waste, transforming two challenging waste streams into a single, high-value product. We propose that the inherent chemical contrast between these feedstocks PJ-WB, rich in oxygen (42.4 wt%), and PO, an oxygen-free and hydrogen-donating polymer (13.07 wt% H) creates a perfect reactive partnership. Our investigation, employing a multi-faceted analytical approach, first reveals that non-catalytic co-pyrolysis unlocks significant synergy. A 70:30 PJ-WB:PO blend boosted bio-oil yield to 57.3 wt%, a notable increase from the 49.3 wt% yield from PJ-WB alone, while simultaneously suppressing char formation. While promising, this initial oil remained hampered by high concentrations of oxygenates and nitrogenates. Seeking to upgrade quality rather than just quantity, we introduced a catalyst to the pyrolysis of pure PJ-WB. This step successfully engineered a superior oil by drastically deoxygenating and denitrogenating the vapors, yet it offered only a marginal improvement in yield. The true breakthrough was achieved by uniting these strategies: catalytic co-pyrolysis. This optimized process successfully harnessed the synergistic yield enhancement of co-processing with the profound upgrading power of the catalyst. The result was a remarkable 59.8 wt% yield of a premium bio-oil, characterized by a dramatic hydrocarbon content of 59.0% and the near-complete elimination of undesirable amides and acids. This work conclusively demonstrates that catalytic co-pyrolysis is more than mere co-processing; it is a engineered system where plastic waste acts as a hydrogen donor to quench and stabilize biomass radicals, while the catalyst directs the reaction pathway towards valuable hydrocarbons. We thus present a sustainable and circular waste-to-fuel technology that not only addresses two critical environmental burdens but also efficiently converts them into a high-yield, hydrocarbon-rich bio-oil, paving the way for advanced biofuel production.