Characterization of biochemical composition of organic resources and prediction of their biodegradation behaviour
Caractérisation de la composition biochimique des ressources organiques et prévision de leur comportement en cours de biodégradation
Résumé
The assessment of agronomic valorization of organic waste after biological treatment is based on the knowledge of the fate of the organic matter (OM) from the waste entering the treatment to the evolution of the product in the soil. It can be predicted through the coupling of models simulating OM evolution during treatment and in soils. It implies to characterize OM biodegradability in the same way for both types of models. The aim of the presented work was thus to link the evolution of the Van Soest fractions, that generally characterize organic inputs in “soils” models, with the oxygen consumption kinetics of the composting process in order to obtain a predicting model of the compost biochemical final characteristics. The oxygen consumption kinetics of four types of organic sources was studied. At several stages of the biodegradation the OM content was characterized as: SOLW (water soluble OM), SOLNDF (OM soluble in neutral detergent), HEM (hemicellulose-like OM), CEL (cellulose-like OM) and LIG (lignin-like OM). Two different pools of OM, with different molecular weight (MW) have been characterized within SOLW. Low MW molecules (< 1,5 kDa) disappeared at the very beginning of the biodegradation, and varied then inversely to the high MW molecules (> 1,5 kDa). CEL and HEM fractions disappeared mostly after the maximum peak of oxygen consumption. SOLNDF decreased only at the end of the biodegradation and LIC was less significantly changed. Based on these observations a new concept of OM dynamics driving the aerobic biodegradation has been proposed.