Locally available biomass (cane chaff) have been successfully polymerised with different substituted phenolic resin copolymers earlier reported (J. Appl. Polym. Sc. 45 (1992) 655-661) with different weight ratios to form biomass cured phenolic composites. The structural integrity has been verified from the study of UV-Vis, FTIR, H-1 NMR measurements of the composites. Thermo gravimetric analysis of the composites has been taken in presence of nitrogen atmosphere. The thermo grams indicate with variation in biomass weight percent resin composite ratio like 10, 30, 50 the composites sustain temperature upto 350-400degreesC showing 80% weight loss which indicates that they can be best used as a heat resisting wood substitute material. (C) 2003 Elsevier Ltd. All rights reserved.