The complementary use of 1H NMR, 13C NMR, FTIR and size exclusion chromatography to investigate the principal structural changes associated with composting of organic materials with diverse origin

The results obtained by 13C CPMAS NMR, 1H NMR and FTIR indicate that, in general, humification seems to be associated with an increase in the aromatic character of the systems, with the presence of phenol groups as principal substituents and a reduction in oxygen containing functional groups, principally carboxylic or carbonylic groups, as well as the development of molecular fractions with larger size. These results also support the suitability of UV-Visible and fluorescence spectroscopies in the assessment of the humification course of humic extracts in composting processes.