EVALUATION OF THE STABILIZATION LEVEL OF PIG ORGANIC WASTE - INFLUENCE OF HUMIC-LIKE COMPOUNDS

The evolution of the organic matter during the maturation of solid sam ples of pig sludges and pig manure composted with straw was followed. A sample of pig sludge about 15 years old also was characterized for c omparison. The organic matter of the composts and sludges was extracte d and the humic (HA) and fulvic acids (FA) were separated. The organic carbon in the total extract (TEC) in the fulvic fraction and in the h umic fraction was determined in order to evaluate the stabilization le vel of the organic matter using some humification parameters. The natu re of the organic extract also was evaluated by characterization with analytical isoelectric focusing (IEF). The results confirm that the de gree of humification (DH) decreases during the first period of maturat ion of the organic matter, because of the degradation of humic and ful vic-like compounds contained into the raw organic materials, while the n it increases progressively for all the maturation period. The data c ollected in this study confirm that the FA fraction could be the main cause of the lack of regularity in the trend of increasing DH as matur ation progresses. The FA/TEC ratio infact decreases progressively for all the maturation period, while the HA/TEC ratio increases. The resul ts obtained in the IEF characterization confirm the validity of this a nalytical technique. Moreover, the results do not appear to be affecte d by the presence of the humic-like compounds. The presence of the ban ds focused at the higher pH values appear to be directly related to th e stabilization of the organic material.