Humic Substances Formed during the Composting of Organic Matter

Abstract

Humic substances (HS) were extracted from separated cattle‐manure compost (CSM) at various stages of decomposition. Carbon‐13 nuclear magnetic resonance (13C‐NMR) and Fourier‐transform infrared (FTIR) spectroscopy measurements were performed on the purified humic acids (HA) as well as crude fiber and chemical analyses. Levels of HS extracted from the CSM samples doubled during the composting (from 377 to 710 g kg−1 organic matter [OM]). The HS were divided into: (i) HA, which increased from 184 to 457 g kg−1 OM; and (ii) a fulvic fraction (FF). The FF was separated on XAD‐8 resin to: (i) fulvic acid (FA), which maintained an unchanged level during composting (80–100 g kg−1); and (ii) a nonhumic fraction (NHF), which increased from 107 to 170 g kg−1 OM during the process. The ratios between the concentrations of these fractions were tested as humification indexes. These indexes changed significantly during the process and were found to correlate exponentially with the composting time, C/N ratio, or both. Quantities of low‐molecular‐weight components (FF and NHF) rapidly increased during the first 40 d of composting and were nearly constant thereafter. The HA and HS contents reached nearly constant values after ∼90 d. Only slight compositional and structural changes in CSM HA were detected with cross‐polarization magic‐angle spinning (CPMAS) 13C‐NMR, FTIR spectra, and chemical analyses. The elemental composition and functional groups of CSM HA resembled those reported for HA of plant residues, peats, and incompletely humified materials. The CPMAS 13C‐NMR spectra of the CSM HA resembled that of lignin. The aromaticity of the HA was about 40% and the lignin content was approximately 60%. The NMR data correlated well with results obtained by FTIR spectroscopy, both indicating that the CSM HA are composed of partially degraded constituents of plant tissue, which still retain to some extent their chemical structures. The major plant components identified in the HA were lignin, carbohydrates, and long‐chain aliphatic structural groups.

Evolution of humic acid-like and core-humic acid-like during high-rate composting of pig faeces amended with wheat straw

“…Adani et al (1999) concluded that although the amount of HAlike relatively increased during composting (in g kg-1 VS), the absolute amount of HA-like decreased, especially at the start of the composting process. Chefetz et al (1998) showed that the coating material bound to core-HA-like was degraded during the composting process and Inbar et al (1990) suggested that HA-like was formed from partially degraded constituents of composted parent materials. Therefore, the humification process can be interpreted as the elimination of interference materials (i.e.…”

Determination of minimal duration necessary for the isolation of humic acid contained in composted pineapple leaves

“…Ten g (dry-weight basis) of compost (at natural moisture level) was placed in polyethylene centrifuge bottles, 100 mL NaOH (0.01 M) [18] 20 ) and 24 h (Et 24 ). At the end of each extraction time, the sides of the bottles were washed with distilled water, and the mixture centrifuged at 7500 rpm for 12 min.…”

Controlling Ammonia Volatilization by Mixing Urea with Humic Acid, Fulvic Acid, Triple Superphosphate and Muriate of Potash

“…Total organic carbon was determined using loss on ignition method [10] . The carboxylic-COOH, phenolic-OH functional groups and total acidity were determined by the method described by Inbar et al [14] . E 4 /E 6 was determined using E 4 /E 6 ratio [13] .…”