Transesterification is by far the most common method to produce biodiesel, and the commercial process is catalytically transesterified by homogeneous acid or base. Non-edible soybean soapstock is found to be a better raw material for the synthesis of biodiesel, because it is relatively centralized. However, such oils usually contain some amounts of water and free fatty acids (FFAs). The FFAs are not converted to esters but soap when homogeneous base catalysts are used. The development and research of novel and efficient ways using solid catalysts for the transesterification of inedible oil into biodiesel are the key industrial challenges. Solid acid catalysts have gained considerable attention due to their advantages of non-corrosion, non-toxicity, water tolerance, and easy separation for recycling.

Dr. Guo Feng of Xishuangbanna Tropical Botanical Garden (XTBG) proposed an effective conversion technique for synthesis of biodiesel from acidified soybean soapstocks by using lignin-derived carbonaceous catalyst (LCC). The preparation method not only reduced the cost and simplified the process, but also made full use of biomass waste. 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 oC 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%).