During the biological treatment of waste organic matter undergoes considerable changes. Degradation and transformation, mineralization and humification take place. These processes correspond to different energy contents, which are reflected by the characteristic thermal behavior of the samples. Waste materials such as compost, municipal solid waste and waste from abandoned landfills have been investigated in this study to demonstrate the applicability of thermal methods in waste management. The use of the total sample, thus avoiding chemical extraction, has proved to be advantageous in the management of complex materials. Nevertheless, waste compounds were also characterized. TG/DTG and the curves of the CO2 ion cur-rent have been recorded in order to shed light on changes occurring in humic acids during composting. Thermal characteristics were attributed to different stages of decomposition of landfill materials. Further to the assessment of unknown landfills process control was carried out to evaluate the efficiency of aeration. A simple procedure that it not based on the comparison of a series of data but rather enables assessment of an individual sample is described for use in the evaluation of organic matter present in municipal solid waste. (C) 2005 Elsevier B.V. All rights reserved.