Waste Plastics as an Effective Binder for Biochar Pelletization

The objective of this study was to investigate the feasibility of using waste plastics as binders to produce high-quality biochar pellets from biochar powders that were made from the pyrolysis of pine sawdust at temperatures ranging from 300 to 450 °C. Plastic binders (virgin and waste) were applied with 5 to 30 wt % of the total mixture. The mixture was pelletized at a maximum pressure of ∼156 MPa. The heating value, density, saturated moisture uptake, energy density, and hardness of biochar pellets were measured to evaluate the pellet quality. The results showed that using plastics as binders could produce strong biochar pellets with the biochar produced at relatively low temperatures (300–330 °C). The optimal fraction of the plastic binder would be between 5 and 10 wt %. The biochar produced at the higher temperature (450 °C) had difficulty forming strong pellets even with binders. The hydrophobicity and higher heating value of pellets were significantly improved by adding plastics as binders. Economic analysis showed that using waste plastics from the local waste recycling program would be an economical way for producing biochar pellets.