Simultaneous Optimization and Heat Integration for Biodiesel Production from Cooking Oil and Algae

In this article, we address the optimal production of second-generation biodiesel using waste cooking oil and algae oil. We consider five different technologies for the transesterification of the oil (homogeneous acid- or alkali-catalyzed, heterogeneous basic-catalyzed, enzymatic, and supercritical uncatalyzed). We formulate the problem as an MINLP problem where the models for each of the reactors are based on surface response methodology to capture the effects of the variables on the yield. The aim is to perform simultaneous optimization and heat integration for the production of biodiesel from each of the different oil sources in terms of the technology to use and the operating conditions to apply. Furthermore, a process network is designed to minimize the freshwater consumption. The optimal conditions in the reactors differ from those traditionally used because the separation tasks are taken into account in this work. For algae oil, the optimal process employs alkali as the catalyst and has a production cost of 0.42$/gal, an energy consumption of 1.94 MJ/gal, and a freshwater consumption of 0.60 gal(water)/gal(ethanol). For cooking oil, the optimal process is the one with the heterogeneous catalyst and has a production cost and energy and water consumption of $0.66/gal, 1.94 MJ/gal, and 0.33 gal(water)/gal(ethanol), respectively.