Production of biodiesel from sewage sludge lipids was catalysed by six different Brønsted acidic imida-zolium and long chain ammonium ionic liquids; both with an alkane sulfonic acid group and with differentanions. Among the ionic liquid tested, 4-(3-methylimidazolium) butanesulfonic acid trifluoromethane-sulfonate, [mimC4SO3H][SO3CF3], was selected as the best catalyst due to its high catalytic performanceand purer biodiesel obtained than the equivalent ammonium ionic liquid, 4-(trihexylammonium) butane-sulfonic acid trifluoromethanesulfonate, [N666(C4SO3H)][SO3CF3]. The influence of different reactionvariables on the biodiesel yield was studied using [mimC4SO3H][SO3CF3] as a catalyst. The yield of fattyacid methyl esters (biodiesel) reached 90% (based on saponifiable lipids) under the following optimisedconditions: 10:1 molar ratio of methanol to saponifiable lipids, 7 wt% ionic liquid catalyst (wt%, based onlipids), 100◦C and 5 h. In addition, the ionic liquid has a good reusability and can be easily separated fromthe biodiesel. These acidic ionic liquids were found to be efficient catalysts for the synthesis of biodieselfrom low-cost and non-edible feedstock like sewage sludge lipids.

doi: 10.1016/j.apcatb.2015.08.039