Optimization and heat and water integration for biodiesel production from cooking oil and algae

In this paper we address the optimal production of second generation of biodiesel using waste cooking oil and algae oil. We consider 5 different technologies for the transesterification of the oil (homogeneous acid or alkali catalyzed, heterogeneous basic catalyzed, enzymatic and supercritical non catalyzed). We formulate the problem as an MINLP where the models for each of the reactors are based on surface response methodology to capture the effect of the variables on the yield. The aim is to simultaneously optimize and heat integrate the production of biodiesel from each of the different oil sources in terms of the technology to use and the operating conditions required. The optimal conditions in the reactors differ from the ones traditionally used because the separation stages were not taking into account in the design. When using algae oil, the optimal process employs alkali as catalyst with a production cost of 0.42$/gal, 1.94 MJ/gal of energy consumption and freshwater consumption 0.60 galwater / galethanol . For cooking oil the optimal process is the one with heterogeneous catalyst, with production cost, energy and water consumption of $0.66/gal, 1.94 MJ/gal and 0.33galwater / galethanol, respectively.