BACKGROUND: The valorization of renewable and abundant resources (date seed, olive stone, corncob, rapeseed cake and apple pomace) from agro-industrial activities was performed by mild liquefaction using polyhydric alcohols to obtain biopolyols that constitute an attractive choice for polyurethanes and other industrial sectors. RESULTS: The results indicated that liquefaction yields above 90% were obtained for almost all resources (except for rapeseed cake residue) at a minimum ratio of 0.25 mass/liquefying solvent by using weight ratio polyethylene glycol : glycerol : sulphuric acid of 80 : 20 : 3, at quite reasonable reaction temperature and time; 160 degrees C and 60 min, respectively. The values determined for hydroxyl number and viscosity in polyols from date seeds were found to be in the range of those typical of commercial polyols used in polyurethane foam production. On the other hand, the multifunctional liquids from apple pomace, olive stone, corncob and rapeseed cake could be used not only as precursor in polyurethane production but also for replacement of a certain amount of the polyhydroxy alcohol in polyester synthesis. CONCLUSION: The results obtained demonstrated the viability of using polyhydric alcohol liquefaction to generate bio-based polyols, thus opening new avenues of exploitation of these by-products. (C) 2011 Society of Chemical Industry