Co-pyrolysis of de-oiled microalgal biomass residue and waste tires: Deeper insights from thermal kinetics, behaviors, drivers, bio-oils, bio-chars, and in-situ evolved gases analyses

The effective utilization of biomass and waste streams has drawn significant attention in light of the energy crisis and requirement for carbon footprint reduction. This study aimed to characterize the pyrolytic behaviors, drivers, kinetics, in-situ evolved gases characteristics, bio-oils, bio-chars, and product distributions of the de-oiled Nannochloropsis sp. residue (NSR) and waste tires (WT) via TG-FTIR-MS and Fixed bed reactor. The D(TG) analysis of the co-pyrolysis was characterized by two decomposition stages: the first stage was the degradation of NSR (150–350 °C), and the second stage (350–550 °C) was ascribed to the degradation of NSR-WT blends. The discrepancy in experimental and theoretical weight loss (ΔW) was less than zero for the blends containing 80, 60, and 50% NSR when the temperature exceeded 210 °C, which confirmed the existence of a strong synergistic effect. The average activation energy (Eavg) was 167.37 kJ/mol and 221.79 kJ/mol for the NSR and WT devolatilization, respectively. To gain more insight into the pyrolytic performance, solid, liquid, and gas products were analyzed by different analytical techniques. The results revealed that the co-pyrolysis significantly modified the chemical composition of bio-oil, leading to an increase in bio-oil yield up to 48.96 wt%. Meanwhile, it seemed conceivable to modify the structure and improve the quality of bio-oils and biochar by co-pyrolysis. This work provides a practical and theoretical understanding of optimizing energy generation, emission control, and products recovery during the co-pyrolysis process.