Optimization of biodiesel production by in situ transesterification from dry biomass of Choricystis minor var. minor via response surface methodology

Abstract

The development of low-cost and cost-effective technologies to produce biodiesel from microalgae is a challenge being addressed by many researchers. This work optimized direct transesterification of dry biomass of Choricystis minor var. minor using H3PO4 and KOH as catalysts. The acid reaction conditions were optimized by Box–Behnken design and the base catalysis by 32 factorial design with replication. The fatty acid methyl ester (FAME) yield was investigated by response surface methodology. The H3PO4 catalyst was able to convert more than 50% of the triacylglyceride into FAME. Applying an analysis of variance, the temperature variable was the most significant factor, followed by reaction time. The interaction between time and temperature also positively influenced the model. The optimum conditions for acid catalysis were H3PO4 solution 10 mL, 60 °C, and 3 h. In base catalysis, the model presented a lower statistical significance, with no significant differences in FAME content. The base catalysis conditions determined were temperature of 30 °C for 1 h. The qualitative and quantitative profile of FAMEs was similar for both designs evaluated. The statistical tool made it possible to optimize the biodiesel production by dry microalgae biomass at lower cost, with less labor and in less time.