Water absorbent polyurethane (PU) rigid composite foam was prepared using polyols derived from molasses and lignin filled with microcrystalline cellulose (MCC) powder with various particle sizes. By combining biomaterial components, preparation conditions were examined in order to obtain PU foams showing reliable water-adsorbing properties. Water absorbing capabilities, such as, water absorbing time, water retention in air as a function of time, and also mechanical properties in dry and wet state, were investigated. Rigid PU composite foams having equilibrium water retention ca. 1.0 g cm(-3), maintain ca. 0.7 g cm(-3) retention water in air after 24 h. Compression strength in the wet state was ca. 50 kPa and compression modulus ca. 1 MPa. MCC acts as a quick water absorbent in the initial stage of water immersion and PU matrix restrains a large amount of water for a long period.