Evolution and qualitative modifications of humin-like matter during high rate composting of pig faeces amended with wheat straw

Abstract During a 4-week period of composting of wheat straw-amended pig faeces, humin (HU)- and core-HU-like matter were isolated by NaOH-Na4P2O7 treatment of the compost bed, respectively, without and with previous extraction by organic solvent and by H2SO4. The changes in the content and elemental composition of both fractions in the compost bed were monitored. Evidence of the compositional changes was also obtained by NMR spectroscopy and by pyrolysis-GC / MS studies. The results indicated that core-HU-like matter was mainly aromatic, while HU contained both core-HU-like and other types of easily degradable organic matter. Correlation of the data found in this study with data from previous studies on humic acid (HA)- and core-HA-like matter in the same composting process indicated that in the time range from 2 to 4 weeks, the weight loss of the core-HU-like matter amounted to 788 g, whereas the weight of total core-HA-like matter increased by 87 g. In spite of the high weight loss, the NMR and pyrolys...