Co-pyrolysis of hydrothermally pre-treated microalgae residue and polymeric waste (plastic/tires): Comparative and dynamic analyses of pyrolytic behaviors, kinetics, chars, oils, and in-situ gas emissions

Biomass and polymeric wastes are becoming more problematic economically and environmentally. Their copyrolysis could be a cost-effective and environmentally preferable alternative for reducing waste quantities and gas emissions, as well as recovering valuable oils, chars, and gases. This study aimed to dynamically characterize the co-pyrolysis of hydrothermally treated Chlorella sorokiniana residue (CSR) and waste polymers (polystyrene (PS) and waste tires (WT)) based on their pyrolytic behaviors, kinetics, interaction effects, biochars, bio-oils, and in-situ evolved gasses characteristics. The devolatilization of CSR mainly occurred between 150 and 500 degrees C, while the decomposition of WT and PS appeared between 200-550 degrees C and 300-550 degrees C, respectively. The average activation energy was 179.25, 222.82, and 223.12 kJ/mol for the CSR, WT, and PS devolatilization, respectively. The TG-FTIR-detected functional groups included C-H- (stretching vibration), C-H- (in-plane & out-of-plane bending vibration), C--C, CO2, O-H, C--O, COOH, C-O, and NH3. The TG-MSdetected pyrolytic products were CHO+, CH3O+, C2H3O+, C3H3O+ C3H6O+, C4H3O+, C5H6O+, COOH+, NH3+, aliphatic, and aromatic hydrocarbons. Moreover, the pyrolytic oil was found to be more stable, with significantly fewer N- and O-containing compounds. It seemed that the inclusion of PS and WT in CSR pyrolysis reduce the additional fuel processing requirements to transform liquid yields into useful fuel. This research findings provide theoretical and practical insights into the control and application potential as well as the limitations of the highvalue energy and products derived from the co-pyrolysis of CSR, PS, and WT.

Automated summary

Biomass and polymeric wastes can be coprocessed to reduce waste quantities and emissions while recovering valuable products. This study characterized the co-pyrolysis of hydrothermally treated Chlorella sorokiniana residue (CSR) and waste polymers (polystyrene (PS) and waste tires (WT)) to understand their pyrolytic behaviors and kinetics. The results show that including PS and WT in CSR pyrolysis reduces the processing requirements for converting liquid yields into useful fuel. The findings provide insights into the control and application potential of the co-pyrolysis process.