The potential application of ultrasonics as a pretreatment process to enhance saccharification of starch in corn-to-ethanol plants is evaluated in this paper. Due to energy intensive use of steam in hydro-cooking, ultrasonics poses a promising alternative as a pretreatment method. Two independent ultrasonic experiments were conducted at a frequency of 20 kHz; batch and continuous flow treatment. Corn slurry was obtained from a nearby ethanol plant and sonicated in batch mode at amplitude of 144µmpeak-to-peak (p-p) for 90 s using a catenoidal horn with a 10 mm diameter face. In the continuous flow treatment, corn slurry was pumped through a reactor equipped with a Branson Ultrasonics “donut horn”. Jet-cooked samples were obtained from the same ethanol plant and analyzed for comparison in fermentation yield. Ethanol yields in sonicated samples were comparable to jet-cooked samples. The glucose levels decreased with consumption during the initial stage of the fermentation and suddenly dropped after 6 h as the ethanol increased. An economic comparison was also conducted on jet cooking and ultrasonics pretreatment methods. The analysis showed that capital cost for the ultrasonics system was higher compared to the capital cost of hydrocooking. However, due to the relatively large energy demand of jet cookers, the operating costs of the hydrocooker suggest that it is cost effective to use ultrasonics.
Available at: http://works.bepress.com/raj_raman/7/