Catalytic co-pyrolysis characteristics and kinetics analysis of food waste and chinar leaves, and the large-scale microwave disposal feasibility

Abstract

Food waste pyrolysis has been reported widely these years. However, rare research discusses its industrial possibilities due to its high moisture content. This research focuses on the microwave co-pyrolysis of food waste and chinar leaves to tune the moisture and seek for solution. To find the optimal path for microwave co-pyrolysis of raw food waste (69 wt.% moisture) and chinar leaves, thermal characteristics, catalysts (Na₂CO₃ and MgO), and kinetics (KAS, OFW, Friedman) were conducted to reveal the pyrolysis behaviors and apparent activation energy in all conditions. Lastly, techno-economic analysis was done to estimate the operating costs of large-scale microwave co-pyrolysis. Results showed that Na₂CO₃ and MgO both suppressed the secondary pyrolysis between 355 and 398 ℃, which is consistent with the modified Broido–Shafizadeh model, respectively. Importantly, CL75-FW25-Na₂CO₃ performed higher pyrolysis rates between 306.7 and 471.7 ℃, and the presence of 5% alkali metal salt significantly lowered the apparent activation energy (from 195.2 to 122.4 kJ/mol, KAS). Moreover, it was found that the biogas collected from 250 to 800 ℃ contained a total of 26.5% H₂, 17% C₂H₆, and 20.9% C₂H₄. The large-scale production cost of microwave co-pyrolysis of raw mixed food waste and chinar leaves is estimated to be USD 536.72 /ton. This research demonstrates that alkali metal salt and synergistic effects between food waste and chinar leaves can optimize the co-pyrolysis process, and its catalytic microwave co-pyrolysis also presents potential economic feasibility for the efficient disposal of solid municipal waste and clean biogas production.