Biodiesel was produced from acidified soybean soapstocks by using lignin-derived carbonaceous catalyst (LCC). LCC was a solid acidic catalyst prepared by direct sulfonation of residual lignin from Xanthoceras sorbifolia Bunge hulls. The textural properties of the catalyst were characterized by C-13 MAS NMR, X-ray diffraction, FT-IR, elemental analysis and BET surface area measurement. When 7 wt.% of LCC was used in the esterification, the maximum free fatty acids (FFAs) conversion (above 97%) could be achieved at a molar ratio of methanol/oil of 1:9 and a reaction temperature of 70 degrees C for 5 h. A comparison of catalytic activity between sulfuric acid and LCC revealed that LCC performed 3.5 times higher activity than sulfuric acid with the equivalent active group (-SO3H). Additionally, LCC could be reused at least three times with high FFAs conversion (>80%). (c) 2012 Elsevier Ltd. All rights reserved.