ARS | Publication request: Nutrient Recovery from the Dry Grind Process Using Sequential Micro and Ultrafiltration of Thin Stillage

Submitted to: Bioresource Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 31, 2009
Publication Date: February 6, 2010
Citation: Arora, A., Dien, B.S., Belyea, R.L., Singh, V., Tumbleson, M.E., Rausch, K.D. 2010. Nutrient Recovery from the Dry Grind Process Using Sequential Micro and Ultrafiltration of Thin Stillage. Bioresource Technology. 101(11):3859-3863.

Interpretive Summary: Micro and ultrafiltration are alternate processes to remove water from complex industrial processing streams. In this paper, we examined the ability of these methods to remove water and enhance the value of an intermediate product associated with corn ethanol termed “thin stillage.” The results were very promising. The membrane operations were successful in concentrating the thin stillage to a solids content similar to the condensed syrup product currently made from thin stillage via energy intensive water evaporation. At the same time, it was effective in recovering protein from the liquid stream, which could add value for when the recovered solids are used for animal feed. Finally, it is expected that the semi-clarified water product off the membranes will aid in promoting water efficiency for producing ethanol from corn.

Technical Abstract: The effectiveness of microfiltration (MF) and ultrafiltration (UF) for nutrient recovery from a thin stillage stream was determined. When a stainless steel MF membrane (0.1 um pore size) was used, the content of solids increased from 7.0% to 22.8% with a mean permeate flux rate of 45 L/m**2/h (LMH), fat increased, and ash content decreased. UF experiments were conducted in batch mode under constant temperature and flow rate conditions. Permeate flux profiles were evaluated for regenerated cellulose membranes (YM1, YM10, and YM100) with molecular weight cut offs of 1, 10, and 100 kDa. UF increased total solids, protein, and fat and decreased ash in retentate stream. When permeate streams from MF were subjected to UF, retentate total solids concentrations similar to those of commercial syrup (23–28.8%) were obtained. YM100 had the highest percent permeate flux decline (70% of initial flux) followed by YM10 and YM1 membranes. Sequential filtration improved permeate flux rates of the YM100 membrane (32.6–73.4 LMH) but the percent decline was also highest in a sequential MF + YM100 system. Protein recovery was the highest in YM1 retentate. Removal of solids, protein, and fat from thin stillage may generate a permeate stream that may improve water removal efficiency and increase water recycling.