Determination of Compost Biomaturity. III. Evaluation of a Colorimetric Test by13C-NMR Spectroscopy and Pyrolysis-Field Ionization Mass Spectrometry

Publisher Website
Google Scholar
Abstract
Four mixtures containing various farmyard manures with or without shredded waste paper were sampled during several stages of composting and extracted with hot water. Freeze-dried extracts of samples from four stages were subjected to 13C-NMR spectroscopy to determine the different types of carbon in them. Similar samples from six stages were analyzed by Pyrolysis-Field Ionization Mass Spectrometry (PY-FIMS) to identify major individual organic components. PY- FIMS revealed the presence of many soluble components, including acetic acid, phenols, lignins, amino acids, quinones and heterocyclic-N compounds during the initial stages of composting. The concentrations of many of these compounds diminished as the compost matured in parallel with decreases in optical density at 665 nm reported earlier. The NMR data confirmed that as concentrations of individual compounds indicated by PY-FIMS decreased, the aromaticity increased as a result of humification to reach its maximum at or near maturity, 59 days after the initiation of composting. These results confirmed the concept that the optical density of water extracts of immature composts was initially due to many intermediate products of decomposition, but then decreased due to formation of new humus which coagulated as the composts matured, thus further decreasing the optical density. The results thus corroborated the earlier suggestion that photometry of compost water extracts could serve as a suitable test for compost biomaturity.