The use of rice bran oil within a biorefinery concept

Background: A waste of the rice production chain, namely bran, can be used to produce an oil with a very high content in free fatty acids (FFA). Due to its very high acidity, this material cannot be used neither to feed power generators nor as raw material for oleochemicals synthesis, and therefore it is not even extracted. Results: Rice bran oil with a content of 84 % in free fatty acids can be converted into a mixture of triglycerides or into useful oleochemicals such as monoglycerides, widely used as emulsifiers in food. Monoglycerides were obtained carrying out a one step esterification + transesterification reaction over an amorphous solid acid. Yields are higher than those obtained by enzymatic transesterification of oil and competitive with the esterification of free fatty acids involving the use of homogeneous acids generating significant amounts of wastewaters. On the other hand, esterification with higher amount of glycerol, a low value by-product of the biodiesel industry, gave an oil with low acidity suitable to feed power generators. Conclusions: The use of solid acid catalysts is a valuable tool for the valorization of rice bran oil. The chance to produce a low acidity oil or monoglycerides in one step from RBO may add value to the whole rice productive chain while setting the stage for the design of biorefineries based on the use of agro-industrial residues