Developing a mini biodiesel production line via sequential conversion to purification from Scenedesmus acuminatus S4 grown in domestic wastewater

BACKGROUND Full demonstrations of the production of microalgal biodiesel from conversion to purification have been reported only rarely in the literature. This study was aimed at developing a mini production line consisting of sequential conversion, extraction and purification of biodiesel from Scenedesmus acuminatus S4 grown in domestic wastewater. RESULTS The data showed that the separated conversion‐extraction (SCE) produced biodiesel with high yield (99.9%) and purity (87.5%) at 200 g L–1 biomass loading, 5% H2SO4/methanol (v/v) catalyst loading, 100 °C reaction temperature and 200 rpm stirring rate, in a 1 h conversion reaction, followed by extraction with hexane (10 mL:1 g dry cell weight) by mixing for 10 min (200 rpm) at 25 °C. The integrated conversion‐extraction (ICE) performed by simultaneous addition of hexane to the biomass and the catalytic solution mixture under the optimized conditions, achieved biodiesel yield and purity of 91.9% and 81.4%, respectively. Crude biodiesel was purified by 40% (w/v) adsorbents [Magnesol and D‐sol® (D60)]/crude biodiesel achieving >95% fatty acid methyl esters (FAME) purity, which is superior to the results in the literature and equivalent to fuel grade standard. CONCLUSIONS Fuel grade biodiesel was successfully produced from S. acuminatus S4 via sequential steps of direct conversion, extraction and purification. The conversion step can be performed via SCE or ICE followed by extraction to obtain crude biodiesel (99% yield and 87.5% purity), whereas the purification step was implemented by dry‐washing with Magnesol or D‐sol® (D60) to >95% FAME. The current production line has technical merits that need to be further optimized for large‐scale application. © 2020 Society of Chemical Industry