Thermal and Kinetic Study of Waste Polypropylene, Cardboard, Wood Biomass, and Their Blends: A Thermogravimetry Approach

In this study, a thermogravimetry approach was employed to investigate the thermal parameters of waste polypropylene (PP), mixed wood biomass (WB), cardboard (CB), and their blends during co-gasification under oxidative conditions at varying heating rates. The resulting data were used to quantify the mass loss profiles for each feedstock and to assess the effects of blending on process temperatures (onset and end), residual mass, and activation energies. Activation energies (Ea) were determined using three iso-conversional methods: Friedman, Kissinger–Akahira–Sunose (KAS), and Numerical Optimization. Among the feedstocks, PP exhibited the highest thermal stability. When blended with either CB or WB, both onset and end temperatures significantly ( p < 0.05) increased with rising PP content. These trends were consistent at heating rates of 20 and 40 °C/min. In contrast, CB/WB blends showed no notable variation in onset temperature across blend ratios at either heating rate. However, PP/CB blends exhibited significantly lower residual masses (up to a six-fold decrease) with increasing PP content. Since both PP and WB individually yielded very low residual mass (<2 wt%), increasing PP content in PP/WB blends did not significantly affect the residual mass. Overall, higher heating rates shifted thermal decomposition into higher temperature regimes in both individual and blended feedstocks, but had no impact on residual mass. The Ea of WB was the highest (138–139 kJ/mol), followed by CB (113–116 kJ/mol) and PP (56–63 kJ/mol). The blending of PP/CB and CB/WB resulted in reduced Ea values compared to the pure feedstocks, indicating a positive synergistic effect during co-gasification. In essence, the co-gasification of mixed plastic waste presents a promising strategy for sustainable waste management and energy recovery.