Improvement in commercial scale dry mill corn ethanol production using controlled flow cavitation and cellulose hydrolysis

Abstract

During commercial-scale dry-mill ethanol production from corn, as much as 6 % of the starch and all of the cellulose remain unconverted. In this study, two methods to improve ethanol production during commercial-scale corn ethanol production were tested that release and hydrolyze these unconverted carbohydrate fractions; controlled flow cavitation (CFC) and enzymatic cellulose hydrolysis. Corn slurry samples were collected from a 379 million liter per year ethanol plant in which a full-scale CFC unit was installed. Samples collected before and after the CFC unit, and after the jet cooker, were compared on three separate occasions. Results showed that CFC reduced the particle size, led to qualitative changes in cell structure, increased total sugars, and reduced total solids after liquefaction. It also led to significant increases in ethanol production and solids conversion during subsequent simultaneous saccharification and fermentation. The effects of CFC alone were greater than those of CFC plus jet cooking, possibly due to the formation of unfermentable products during jet cooking. On average, ethanol production from cavitated samples was 2.2 % greater than from uncavitated samples. Cellulase addition to uncavitated and cavitated samples led to significant 3.2 and 4.3 % increases in ethanol yield, respectively. The electrical energy used for CFC was 1/16th of that in the additional ethanol produced and the ethanol value was more than 38 times the cost of the additional electricity used. This indicates that CFC can both efficiently increase corn ethanol yields and reduce the amount of energy needed to produce it. © 2013 The Author(s).