Application of various statistical methods to evaluate thermo-analytical data of mechanically-biologically treated municipal solid waste

Resource recovery and stabilization of waste organic matter before landfilling are crucial issues in waste management. These requirements are closely related to efficient separation of recyclables and well operated biological processes. Adequate analytical methods are a prerequisite to verify the realization of these purposes. A large data pool of mechanically-biologically treated (MBT) municipal solid waste originating from different Austrian treatment plants was investigated using simultaneous thermal analysis that comprises thermogravimetry/mass spectrometry (TG/MS) and differential scanning calorimetry (DSC). Biodegradation of MBT-waste is paralleled by decreasing enthalpies. Referring to organic matter enthalpy increases with progressing stabilization. Evaluation of thermal data was supported by multivariate data analysis. The efficiency of the biological pretreatment of municipal solid waste (MSW) compared to untreated MSW in landfills was verified by principal component analysis (PCA) of heat flow (DSC) profiles. Divergent input materials were identified by means of heat flow profiles and discriminant analysis (PLS-DA). Prediction models for the calorific value and the TOC (total organic carbon) based on DSC-profiles and partial least squares regression (PLS-R) resulted in a good correlation (R2 = 0.94 in both cases). The root mean square errors of crossvalidation were 413 J g-1 and 1.5% referring to dry matter, respectively. Respiration activity (RA4) was reflected by thermal analyses. The correlation was based on mass spectra of volatile combustion products and DSC-profiles. The correlation resulted in a coefficient of determination (R2) of 0.87 and 0.82 respectively. Thermal analysis in association with multivariate statistical methods has proven to be a reliable method to verify efficient separation of the plastic fraction, stabilization by biological treatment and waste material composition.