Integrated biofuels process synthesis: integration between bioethanol andbiodiesel processes

Second and third generation bioethanol and biodiesel are more environmentally friendly fuels than gasoline and petrodiesel, andmore sustainable than first generation biofuels. However, their production processes are more complex and more expensive. In this chapter, we describe a two-stage synthesis methodology for integrating both biodiesel and bioethanol processes. In the first stage, to minimize unit production costs we screened different technological paths by formulating a mixed integer nonlinear problem superstructure solved in GAMS. In the second stage, we intensified one portion of the optimal technological path.We used the concept of column section recombination and employed Aspen Plus V8.8 and its economic evaluation tool to evaluate the structural changes. The first stage identified the optimal technological routes and the integration of bioethanol (30% used for biodiesel process), glycerol (10% used for bioethanol process), and steam and electricity from combustion (54%used as electricity) in the bioethanol and biodiesel processes. In the second stage, we saved about 5% in equipment costs and 12% in utility costs for bioethanol separation. This dual synthesis methodology, consisting of a top-level screening task followed by a down-level intensification task, proved to be an efficient methodology for integrated biofuel process synthesis. The case study illustrates and provides important insights into the optimal synthesis and intensification of biofuel production processes with the proposed synthesis methodology