Peat, plant matter that is partially fossilized, is formed in poorly oxygenated wetlands where the rate at which the plant matter accumulates is greater than the rate at which it decomposes. Peat is a common solid fuel ranked among coal, coke, wood, and sugarcane bagasse. Peat has also been used to recover oil during the soil and water remediation processes. However, industrial utilization of peat in thermochemi cal conversion systems to liberate energy requires the knowledge of its thermal characteristics. In this study, the thermal behavior of peat (both uncontaminated and dieselcontaminated) was examined at three heating rates (10, 20, and 50 C min) in a stationary air atmosphere using a thermogravimetric analysis technique between ambient temperature (25C)and 600 C. The thermal degradation rate in active and passive pyrolysis zones, the initial degradation temperature, and the residual weight at 600 C were determined. Increasing the heating rate increased both the thermal degradation rate and the residual weight at 600 C and decreased the initial degradation temperature. The residual weight at 600 C was less than the ash content in all of the peat samples indicating the burnout of some of the mineral oxides, which have low melting and boiling temperatures, such as K2O and P2O. The results provide useful information about utilization of diesel-contaminated peat in thermochemical conversion systems, especially gasifiers, because of its high energy content and low ash content.