Biodiesel production from Halamphora coffeaeformis microalga oil by supercritical ethanol transesterification

Abstract

The marine benthic diatom Halamphora coffeaeformis is a potential feedstock for biodiesel production. Thisspecies shows high growth rates, important triacylglycerol (TAG) contents and grows in seawater makinglarge-scale cultivation advantageous. Moreover, sustainable biofuel production in future biorefineries requiresthe implementation of technologies that employ renewable solvents. Thus, the goal of this work was to evaluateethanol usage as extraction solvent and reaction medium for biodiesel production from H. coffeaeformis. Ina first step a bio-oil extraction was carried out comparing ethanol and n-hexane to investigate the performanceof ethanol with respect to a conventional solvent. Then, a free-catalyst supercritical ethanol transesterificationof the bio-oils was carried out to obtain biodiesel. Higher lipid extraction yields were obtained using ethanolrespect to n-hexane (26wt.% vs 21.1wt.%). The transesterification of crude lipids extracted with ethanol as solventat 305°C and 40min. produced up to 15.9wt.% of biodiesel respect to dried biomass processed. Comparablebiodiesel yields were obtained using non-renewable organic solvents and a conventional catalytic technology.Thus, ethanol extraction and subsequent supercritical transesterification of H. coffeaeformis oil proved to be technicallyfeasible and environmental friendly technology for the production of biodiesel.