In this study, the olive cake was successfully developed and applied as a substrate to produce a lignin based catalyst for biodiesel production. Three lignin-based solid acid catalysts were prepared from the incomplete carbonized alkali lignin using concentrated sulfuric acid. The catalyst underwent a detailed characterization analysis in terms of its functional groups of active sites, surface area, acid sites density and morphological structure. For the catalytic activity test, prepared catalysts were studied for their ability to catalyze both esterification and transesterification reactions of waste vegetable oil (WVO) approximate to 2 FFA (% w/w). The results revealed that a sulfonated lignin-derived acid catalyst has a high potential to esterify waste vegetable oil to about (92%) conversion. Furthermore, it demonstrated about 57% conversion to fatty acid methyl esters (FAME) under the following optimum condition: sulfonation time of 1 h, catalyst loading of 10 wt %, the methanol-to-WVO molar ratio of 35:1, a reaction temperature of 65 degrees C and reaction time of 6 h. Also, the results showed that the lignin-based acid catalyst can be reused at least ten times with high FFA conversion (>75%). (C) 2018 Elsevier Ltd. All rights reserved.