Reaction kinetics of three varieties of barley straw (Kadeth, Laurier, and Leger) were studied at a heating rate of 20 degrees C/min in an oxidizing atmosphere of 15% oxygen and 85% nitrogen using thermogravimetric analysis (TGA) and differential thermal analysis (DTA) techniques. The thermal degradation characteristics and the kinetic parameters (order of reaction, activation energy, and pre-exponential factor) were determined for the two reaction zones from the TGA and DTA curves. Thermal degradation rates in the first reaction zone were relatively higher than those in the second reaction zone. The thermal decomposition of the straw variety Kadeth started at a lower temperature (186 degrees C) than the straw varieties Laurier (229 degrees C) and Leger (223 degrees C). Residual weights recorded at 700 degrees C were in the range of 4.3-7.2%. Higher activation energies (85.4-103.2 kJ/mol) and pre-exponential factors (0.73 x 10(7)-49.10 x 10(7)) were obtained for all varieties of barley straw in the first reaction zone as compared to those of the second reaction zone (34.8-58.6 kJ/mol and 0.27 x 10(2)-14.43 x 10(2) for the activation energy and pre-exponential factor, respectively). The order of reactions were in the range of 2.0-2.3 and 1.1-1.2 for the first and second reaction zones, respectively.