Chemical properties and solid-state CPMAS 13C-NMR of composted organic matter

Abstract

13C NMR spectra acquired with Cross-Polarization Magic Angle Spinning (CPMAS) were used to study solid and finely ground samples of decomposing organic matter. Compost prepared from separated cattle manure (CSM - the solid fraction obtained by centrifugal separators from a slurry of cattle manure) at the start and maturity stages of the composting process was investigated. CPMAS 13C NMR spectra exhibited an increase in aromaticity and carboxyl groups content and a decrease in carbohydrates during composting. The CPMAS 13C NMR measurements agreed with those of crude fiber analyses. Cation exchange capacity increased from 62.8 to 180.9 meq/100g OM, while the C/N ratio decreased from 27.2 to 8.7 along the composting process. The procedure proposed to conduct CPMAS 13C NMR and FTIR measurements directly on ground decomposing organic matter without the application of extractions was shown to provide useful information on the decomposition process.