Characterization of different decomposition stages of biowaste using FT-IR spectroscopy and pyrolysis-field...

The decomposition stage and stabilization of organic matter in biowaste (mixture of yard waste and kitchen waste), originating from an open windrow process, were investigated using Fourier transform infrared (FT-IR) spectroscopy and pyrolysis-field ionization mass spectrometry (Py-FIMS). These investigations provided detailed information about chemical constituents and their behavior during the composting process. The chemical compounds were classified by their molecular signals in Py-FIMS. Multivariate statistical analysis revealed, that during the composting process, the group containing lipids, fatty acids and other chemical compounds with aliphatic skeletons changed the most. Corresponding with Py-FIMS findings changes were observed in absorbance bands of infrared spectra that reflect this group of organic compounds: the aliphatic methylene bands at 2925 and 2850 cm(-1), the band of C=O vibrations of carboxylates at 1640 cm(-1) , the O-H in-plane bend of carboxylic acids, the CO2 stretch of carboxylates and the CH2 group of alkanes at around 1430 cm(-1). During decomposition these bands decreased up to a steady level that indicated stabilization. The band at 1260-1240 cm(-1) that can be assigned to the C--O stretch of carboxylic acids or to the C-N stretch of amides and the band of aromatic amines at 1320 cm(-1) disappeared completely. The nitrate band at 1384 cm(-1) appeared at a later stage of the composting process. The relative increase of chemical compounds like moieties of lignin, humic acids and tannins in the composted material contributed to the aromatic C=C band at around 1640 cm(-1).