Investigation of ethyl biodiesel via transesterification of rice bran oil: bioenergy from residual biomass in Pelotas, Rio Grande do Sul - Brazil

Abstract

The energy sector in Brazil produces liquid biofuels as bioethanol and biodiesel. The most common technique to produce biodiesel is the transesterification of oils extracted from biomass. Rice processing generates grain bran, an agricultural residue. Brazil is one of the main countries that produce this grain. Therefore, the objective of this study was to produce a renewable biofuel using vegetable oil from grain bran via homogeneous basic transesterification. There are only three experimental studies reported in the literature on the production of biodiesel from rice bran oil via alkaline transesterification. Furthermore, the studies do not include results regarding biodiesel acidity, iodine, saponification and moisture content. Although potassium hydroxide (KOH) is the most commonly deployed alkaline catalyst in industrial biodiesel production, there are no reports regarding ethyl biodiesel production using rice bran oil with this catalyst. Therefore, this study applied a factorial arrangement in the experimental phase to produce ethyl biodiesel from rice bran oil using KOH as a catalyst on transesterification. The factors including reaction time, alcohol/oil molar ratio and amount of catalyst allowed to determine the best conditions for biodiesel production. To determine the viability of the biodiesel production, it was necessary to analyze the main parameters required by the national standards, which were kinematic viscosity, iodine index, acidity index, saponification index and moisture. All the yielded biodiesel were complied with the standards of ANP, ASTM and EN, except kinematic viscosity, which ranged from 8.061 to 22.791 mm2s-1. According to the conditions of the factorial arrangement, the calculated kinematic viscosity indicated the need to raise the proportion of catalyst and/or the molar ratio between ethanol and KOH The lower kinematic viscosity, around 8–9 mm2s-1, occurred with 1.5% catalyst and, in general, with molar ratio 9:1. These results suggest that future studies could explore the production of high-quality ethyl biodiesel using rice bran vegetable oil. According to the results, it represents a viable possibility to produce fully renewable and sustainable biodiesel within the socio-economic, environmental and agricultural context in Brazil.