Analysis of humic acids from aerated and non-aerated urban landfill composts

In this investigation, the effect of aeration plus watering on maturation of compost from an urban waste landfill were evaluated. Based on the Dewar assay, composts from non-aerated locations on the site (plots Z1, Z2, Z3) and aerated but not watered site A1 were still far from maturity compared to the compost from the aerated and watered plot A2. This was confirmed from chemical and physico-chemical analyses of the humic acids extracted from these composts. Elemental analysis showed that humic acids from area A2 exhibited features indicating higher contents of aromatic compounds and higher degrees of polymerization and condensation compared to those of areas Z1, Z2, Z3 and A1. These results were confirmed by the values of the E4/E6 and E3/E5 absorbance ratios which were much lower for humic acids from A2 than for the other samples and which can be related to the high oxygen contents and molecular weights of the humic acids. Fourier transform infrared and nuclear magnetic resonance 13C spectral analyses also confirmed that aromatic carbons were more abundant in the humic acids extracted from sample A2. Altogether data show the importance of aeration and watering of landfill compost to achieve rapid maturation of the humic acid.