The possibilities of utilization of stillage from the production of bioethanol on starch feedstocks

Abstract

In Serbia, the industrial production of bioethanol still relies on conventional energy crops (corn, wheat triticale and molasses). The production process generates large amounts of waste liquid stillage (app. 13 hL per hL of bioethanol produced) with high BOD, values which may cause serious environmental problems if not treated adequately. The aim of this paper is to provide an overview of the possibilities of stillage utilization from bioethanol production on starch based feedstocks. Three main approaches were analyzed and presented: (1) recirculation of liquid corn stillage in mashing process; (2) employment of solid corn stillage remained after ethanol distillation as animal feed; (3) utilization of three different liquid stillages for the production of lactic acid. It has been shown that the bioethanol yield can be significantly increased by the recirculation of liquid corn stillage in the amount from 10 to 30%, while the solid fraction can be used as a high quality feed rich in proteins and minerals. In addition, very high values of lactic acid yields were accomplished during lactic acid production on three different liquid stillages by Lactobacillus genera. All of the investigated approaches can significantly improve the economy of bioethanol production on starch grains.