Optimal integration for biodiesel production using bioethanol

In this paper we optimize the production of biodiesel using bioethanol from algae following four different transesterification paths: alkali, enzymatic and heterogeneous catalysts and supercritical conditions. The reactors are modelled using response surface methodology based on experimental results from the literature. These reactor models are implemented together with short-cut methods for the other equipment (distillation column, gravity separators, etc.) in order to recover the ethanol, separate the polar and non polar phases and purify the glycerol and biodiesel produced to formulate the problem as a superstructure of alternatives. The aim of this paper is to simultaneously optimize and heat integrate the production of biodiesel using ethanol in terms of the reaction technology and the operating conditions. The optimal conditions in the reactors differ from the ones traditionally used simply because these results take the separation stages into account. In terms of the best process, currently the alkali catalyzed process is the most profitable while the enzymatic based one is even more promising due to the lower consumption of energy and water, however it requires that the enzyme cost is reduced.