Evaluation of commercial compost quality.

FT-IR spectra, C-13 CP-MAS NMR spectra and molecular weights were also assayed on humic acids extracted from the composts. The results show that the origin of the starting materials affects the quality of the end products especially for their heavy metal content and genotoxic effect. The presence of a high percentage of low molecular weight fractions generally recorded in the humic acids from commercial composts could be due to uncorrected composting process. FT-IR and C-13 CP-MAS NMR spectra agree with functional group assignments, characterising the level of humification. The results show that commercial composts can display harmful properties probably due to the origin of the starting material, therefore a regulation about both compost production and characterisation should be suitable.