Study of Structural Changes in Organic Matter During the Composting and Vermicomposting Production

Composting and vermicomposting are two efficient methods to recycle organic wastes. In order to investigate the structural changes in organic matter during the composting and vermicomposting processes، cattle manure and filter-cake of sugar cane were incubated with and without earthworm''s presence in a controlled temperature and moisture condition for 16 weeks. Compound samples were taken at 0، 8، and 16 weeks. Carbon، nitrogen and C: N ratio were measured by a CN analyzer apparatus. Solid samples were used for structural analysis using FTIR and solid state CP MAS 13C NMR devices. C: N ratio was decreased with improving decomposition process. The C: N ratio was slightly elevated after 16 weeks of vermicomposting. Structural analysis with both spectroscopic methods showed a decrease of O-alkyl C and increase of aromatic and carboxylic functional groups. The analysis of samples with 13C NMR showed that after 16 weeks، the percentage composition of O-alkyl filter-cake decreased from 41 percent in the first sample to about 33. 1 percent. The amount of these compounds in manure samples decreased from 56. 7 percent to 43. 6 percent. Aromatic compounds in samples of raw filter-cake and manure increased from 12. 5 and 13. 5 percent to 16. 4 and 18. 7 percent، respectively. Percentage of carboxyl compounds increased، respectively، from 8. 5 and 5. 6 percent to 9. 7 and 7. 2% in the filter-cake and manure sample. Vermicomposts had higher content of aromatic groups compared to composts (In manure samples 18. 7 instead of 17. 1 percent). After 16 weeks of incubation the aromatic and carboxylic compounds slightly decreased in the vermicomposting process. Analysis of composts and vermicomposts with FTIR and 13C NMR resulted in similar signals with the different frequency intensities. There was a suitable correlation (r=0. 897**) among the spectroscopic methods in characterization of composts and vermicomposts