A critical review on the role of algal biomass in co-pyrolysis: Mechanism, influencing factors, challenges and prospects

• Microalgae and macroalgae exhibit distinct pyrolytic behaviors and product profiles. • Principle and influence parameters of algal co-pyrolysis are reviewed. • Algal co-pyrolysis shows synergy with lignocellulose, sludge, plastics, etc. • Challenges include algal cost, technical complexity, and scalability limitations. • Future prospects: scalable supply, synergy control, catalytic pathways. Algal biomass, as a promising third-generation bioenergy feedstock, is considered a promising source for sustainable biofuel production through pyrolysis due to its high organic content and rapid growth rate. While, co-pyrolysis of algal with diverse feedstocks can significantly enhance the process benefit through synergistic effects. This review summarizes the differences in chemical composition between microalgae and macroalgae and their influence on the distribution of pyrolysis products. Particular attention is given to the principles, influencing factors, and synergistic mechanisms of algal co-pyrolysis. Building on recent research advancements, the effects of diverse co-feedstocks (Lignocellulose, sludge, and plastics, etc.) on pyrolysis performance are expounded, with emphasis on experimental findings and innovations in process parameter optimization. Despite the environmental and resource utilization advantages of algal co-pyrolysis, its commercialization is still hindered by high feedstock costs, technical complexity, and insufficient process optimization. Future research is expected to focus on stable and scalable algae supply, precise and controllable synergistic effects, full-scale co-pyrolysis and efficient catalytic co-pyrolysis.