Pyrolysis of raw and anaerobically digested organic fractions of municipal solid waste: Kinetics, thermodynamics, and product characterization

Abstract

Treating the solid residue after anaerobic digestion (AD) of the organic fraction of municipal solid waste (OFMSW) is currently a challenge. Here, pyrolysis is a promising way of recovering energy and materials from these solid residues. Thus, the objective of this study was to investigate the pyrolysis performance of these solid residues. The effect of AD on the pyrolysis of OFMSW was also studied. Thermogravimetry (TG), differential thermal analysis (DTA), and bench-scale pyrolysis experiments were performed by using OFMSW and anaerobically digested OFMSW. Mathematical deconvolution analysis (MDA), model-free methods, and model-based methods were applied to study the kinetics. Thereafter, thermodynamic parameters were estimated based on the deduced kinetic results. The char, liquid, and permanent gas products from bench-scale experiments were characterized. The pyrolysis results show that the activation energies of the pseudoreactions of OFMSW are higher than those of the corresponding pseudoreactions of digestate. Moreover, the entropy reduction for digestate is larger than that for OFMSW. The characterization results of the products from the bench-scale experiments show that the interactions among feedstock components (lipids, lignocellulose, and proteins) during pyrolysis are enhanced by the application of AD. However, the pyrolysis yields of both heavy organics and gas are inhibited by the application of AD, while the char yield shows the opposite trend.