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

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.