Transformation of dissolved organic matters in swine, cow and chicken manures during composting

The changes of dissolved organic matters (DOMs) extracted from swine, cow and chicken manures were assessed by Fourier transform infrared, ultraviolet, gel permeation chromatography (GPC), excitation–emission-matrix fluorescence (EEM-FL), Biolog Eco and 1H NMR during 60-day composting. Pumice was adopted to eliminate the disturbing of common organic bulking agents. The results showed chicken manure had the highest DOC, DTN (dissolved total nitrogen) and lowest DOC/DTN among the three manures; cow manure had the highest volatile solids, lowest DTN, slowest DOMs hydrolysis rate and the fastest bio-stabilization rate. 1H NMR showed the decrease rates of OC band and saturated carbon chain were distinctly faster than that of olefinic and aromatic structures. The molecular size distribution of DOMs in the three manures was in the range of 1–10 kDa detected by GPC. Microbial carbon utilization capacity decreased in cow manure with composting time, but the contrast was observed in the chicken and swine manures.