Comparative study on pyrolysis characteristics of common fractions from real municipal solid waste using Py-GC/MS and principal component analysis

Efficient thermal conversion of municipal solid waste (MSW) requires a mechanistic understanding of real, heterogeneous waste, yet most mechanistic studies rely on simplified or simulated MSW, leaving the molecular-level impacts of real heterogeneity insufficiently understood. This study aims to systematically characterize pyrolysis of real MSW fractions and evaluate the influence of sample- and temporal-scale heterogeneity. Two MSW samples were collected from an incineration plant on the same day (morning vs. afternoon), classified and cryogenically milled to assess achievable laboratory homogeneity and temporal heterogeneity. Pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) was conducted based on thermogravimetric profiles. Principal component analysis (PCA) was applied on the results to jointly distinguish MSW fractions and quantify heterogeneity effect via distances in principal-component space. PCA revealed a distance pattern of technical replicates < inter-batch < inter-fraction, confirming sufficient homogenization by cryogenic milling and detectable temporal variability in real MSW. Real MSW predominantly produced hydroxyacetaldehyde and levoglucosan from biomass-based fractions (Paper, Cloth, Wood, Kitchen Waste) and styrene from Resin. These differed from those reported for simulated MSW, e.g., acetic acid (sawdust), D-allose (cotton clothes), acetic acid (vegetables), underscoring the importance of using real MSW in mechanistic investigations. Increasing temperature shifted biomass volatiles from anhydrosugars toward carbonyls and gases, while Resin evolved from benzene and straight-chain compounds to cyclic species. The PCA-based distance framework in this study provides a methodological approach for quantifying heterogeneity, assessing representativeness, and improving the reliability of lab micro-scale analyses of real MSW.