Agricultural wastes from Thai cassava plantations are proposed as an important source of energy and their thermochemical properties are determined in this study. These include proximate, ultimate, structural, inorganic matter, heating value, and thermogravimetric analyses. The results show that the agricultural wastes have high volatile contents (78-80%, dry basis) and contain 51% carbon, 7% hydrogen, 41% oxygen, 0.7-1.3% nitrogen, and <0.1% sulphur. Structural analysis reveals that cassava residues are composed of about 36% cellulose, 44% hemicellulose, and 24% lignin. The main inorganic elements found are potassium, phosphorus, and calcium. The lower heating values (LHV) of the biomass are approximately 18 MJkg(-1). The results indicate that cassava wastes contain high volatile, very low nitrogen and sulphur, and rather low lignin with a medium heating value, suggesting that a high quality and environmentally benign bio-fuel could be produced via thermochemical conversion processing like fast pyrolysis.