The aim of this work was to study the potential of biofuel and biomass processing industry side-products as acid catalyst. The synthesis of carbon cryogel from lignin-furfural mixture, prepared via sol-gel polycondensation at 90 degrees C for 0.5 h, has been investigated for biodiesel production. The effect of lignin to furfural (L/F) ratios, lignin to water (L/W) ratios and acid concentration on carbon cryogel synthesis was studied. The carbon cryogels were characterized and tested for oleic acid conversion. The thermally stable amorphous spherical carbon cryogel has a large total surface area with high acidity. Experimental results revealed the optimum FAME yield and oleic acid conversion of 91.3 wt.% and 98.1 wt.%, respectively were attained at 65 degrees C for 5 h with 5 wt.% catalyst loading and 20: 1 methanol to oleic acid molar ratio. Therefore, carbon cryogel is highly potential for heterogeneous esterification of free fatty acid to biodiesel. (C) 2015 Elsevier Ltd. All rights reserved.