Insights into algae-plastic pyrolysis: Thermogravimetric and kinetic approaches for renewable energy

With the rising demand for sustainable energy, biomass pyrolysis has gained significant attention. This study investigates the pyrolytic and kinetic characteristics of Chaetomorpha sp. Algae, three types of plastic waste—polypropylene (PP), high-density polyethylene (HDPE), and polyethylene terephthalate (PET)—and their blends as co-feedstocks. Thermogravimetric analysis (TGA) and the Coats-Redfern kinetic model were utilized to evaluate thermal behavior, synergistic effects, and activation energy. This study is crucial for successful experimental design, facilitating commercial scale-up, and ensuring efficient biomass utilization. Results revealed significant synergistic effects between algae and plastic feedstocks, with mass loss improvements of up to 48.35 % and heating value enhancements of up to 17.53 %. The interaction between feedstocks optimized thermal decomposition and improved energy output, with stronger synergistic effects observed when the degradation temperature ranges of the feedstocks were closely aligned, in which PP > HDPE > PET. This insight serves as a guideline for selecting optimal co-feedstocks in future experiments although further verification is needed by using other feedstocks. Moreover, the addition of plastic waste increased the highest activation energy from 29 kJ/mol to 44 kJ/mol, a value still lower than that of most terrestrial biomass and pure plastics, highlighting the potential of algae-plastic blends for producing biofuel and biopolymer. In conclusion, integrating macroalgae and plastic waste in pyrolysis presents a promising pathway for sustainable energy and waste management, offering valuable insights for scientists and researchers in the field of sustainable energy and environmental sustainability toward net-zero emissions.