Organic matter transformations in lignocellulosic waste products composted or vermicomposted (eisenia fetida andrei): Chemical analysis and 13C CPMAS NMR spectroscopy

Lignocellulosic wastes (of maple) were composted and vermicomposted for 10 months under controlled conditions. Chemical and 13C CPMAS NMR spectroscopic analyses were made to characterize the transformations of the organic matter. At first, the total organic matter and carbon mass underwent a relatively rapid decrease. There was a concomitant decomposition of polysaccharides including cellulose. The degradation of aromatic structures and lignin began after one month of composting. The rapidity of this process was at its greatest during the following three months. NMR analysis showed that more ligninolysis occurred in the vermicompost, which was not apparent from the chemical analyses. The C-to-N ratio decreased, reflecting the changes in the C fractions as well as a higher proportion of N in the vermicompost. Polycondensation or neosynthesis was observed during the final stages. The two types of compost evolved differently: a higher proportion of aromatic compounds, polysaccharides and a lower aromaticity ratio occurred in the vermicompost as well as an increase of the ionic protein-to-organic matter ratio, which are interpreted as a more advanced developed state of humification.