Economic analysis of ethanol and fructose production by selective fermentation coupled to pervaporation: effect of membrane costs on process economics

This work presents a preliminary economic analysis of the production of ethanol using different fermentation processes. The installation of a new plant and the adaptation of an existing ethanol plant to the selective fermentation of glucose from sugar cane hydrolysate were considered. In the latter process, glucose is converted to ethanol and fructose accumulates in the fermentation broth. The use of pervaporation for continuous removal of ethanol from the fermentation broth is also considered, in order to minimize inhibition of the microorganism and to facilitate product recovery. The results show that the selective fermentation coupled to membrane processes to removal of ethanol is an attractive process to increase ethanol production economics, although membrane performance and costs should still be improved.

In this work the preliminary economic analysis of a continuous selective fermentation coupled to pervaporation for ethanol removal is described. The internal return rate (IRR) method was used and two distinct projects were evaluated. The first case considered the installation of a completely new plant, while the second assumed that an existing ethanol plant from sugarcane was available to be adapted to the proposed process. It could be concluded that in both cases, selective fermentation with the production of fructose as a byproduct, coupled to pervaporation for continuous ethanol represents a very promising alternative to increase ethanol process economics. It was observed that the variable costs that involve the installed membrane area are the ones that most influence process viability. For a complete plant installation the highest membrane cost allowed to keep the project feasible is around US$ 500/m2, while the adaptation of an existing plant allows to spend up to US$ 800/m2, considering a minimum return rate on the investment of 17%. After optimization of operation conditions an increase in the process attractiveness is still expected.