Sustainability evaluation of biodiesel produced from microalgae chlamydomonas sp grown in brewery wastewater

Abstract

This study performs a sustainability evaluation of biodiesel from microalga Chlamydomonas sp. grown in20 % (v/v) of brewery's wastewater, blended with pentose sugars (xylose, arabinose or ribose resultingfrom the hydrolysis of brewer's spent grains (BSG). The life cycle steps considered for the study are:microalgae cultivation, biomass processing and lipids extraction at the brewery site, and its conversion tobiodiesel at a dedicated external biofuel's plant. Three sustainability indicators (LCEE, FER and GW) wereconsidered and calculated using experimental data. Literature data was used, whenever necessary, tocomplement life cycle data, thus allowing a more accurate sustainability evaluation. A comparativeanalysis of the biodiesel life cycle steps was also conducted, with the main goal of identifying which stepsneed to be improved. Results show that biomass processing, especially cell harvesting, microalgaecultivation, and lipids extraction are the main process bottlenecks. It is also analysed the influence on themicroalgae biodiesel sustainability of adding each pentose sugar to the cultivation media, concluding that itstrongly influences the biomass and lipid productivity. In particular, the addition of xylose is preferable interms of lipid productivity, but from a sustainability point of view, ribose is the best, though the differencefrom xylose is not significant. Nevertheless, culture without pentose addition presents the bestsustainability results.