Chemical and biological characterization of organic matter during composting of municipal solid waste

Composting of municipal solid waste (MSW) was studied in an attempt to elaborate transformations of organic matter (OM) during the process and define parameters for the degree of maturity of the product. Composting was performed in 1-m³ plastic boxes and the following parameters were measured in 13 samples during 132 d of composting: temperature, C/N ratio, ash content, humic substance contents, and fractions (humic acid, fulvic acid, and nonhumic fraction-HA, FA, and NHF, respectively). Spectroscopic methods (CPMAS ¹³C-NMR, DRIFT) were used to study the chemical composition of the OM. A bioassay based on growth of cucumber (Cucumis sativus L. cv. Dlila) plants was correlated to other parameters. The C/N ratio and ash content showed a typical high rate of change during the first 60 d and reached a plateau thereafter. The HA content increased to a maximum at 112 d, corresponding to the highest plant dry weight and highest 1650/1560 (cm^{- 1}/cm^-1) peak ratios calculated from DRIFT spectra. ¹³C-NMR and DRIFT spectra of samples taken from the composting MSW during the process showed that the residual OM contained an increasing level of aromatic structures. Plant-growth bioassay, HA content, and the DRIFT spectra indicated that MSW compost described in this study, stabilized and achieved maturity after about 110 d.