Parametric Modelling Study to Determine the Feasibility of the Co-Gasification of Macroalgae and Plastics for the Production of Hydrogen-Rich Syngas

Seaweed is of importance to the environment due to properties such as its CO2 sequestration capability. On the other hand, plastic is a versatile material important to society. Unfortunately, the abundance of both plastics and seaweed represents a challenge due to the need of adequate waste management. At first, algae and plastics might not appear suitable for energy recovery; however, with co-gasification, the results are promising. This work presents a model to simulate the co-gasification of Chlorella vulgaris, Sargassum fluitans, and Sargassum natans with plastics. The effect of the gasification temperature (650–850 °C), equivalence ratio (0.25–0.45), and plastics/biomass ratio (0.0–1.0) on the produced gas’s lower heating value, tar concentration, and composition is assessed. Moreover, the environmental performance of using plastic to enhance the syngas produced from the co-gasification with sargassum is assessed using the life cycle assessment methodology. The results indicate that the lower heating value increases with the temperature and plastics/biomass ratio. Moreover, tar increases with the quantity of plastics, varying between 20 and 50 g/Nm3. Finally, adding plastics to algae during gasification reduces the variability in the syngas composition, simplifying the post-processing stage. With respect to environmental performance, gasification has an impact similar to those of pyrolysis and recycling, but the performance could improve with sufficient research and development.