Submitted to: Applied Engineering in Agriculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/9/2011
Publication Date: 5/1/2011
Citation: Hicks, K.B., Wilson, J., Flores, R.A. 2011. Progressive hull removal from barley using the Fitzpatrick comminuting mill. Applied Engineering in Agriculture. 27(5):797-802. Interpretive Summary: Ethanol plant owners want to use barley as a feedstock to make fuel ethanol, but barley has a very abrasive hull that damages the grain handling and fermentation equipment at ethanol facilities. Furthermore, barley hull is not fermentable and therefore just takes up space in the ethanol production equipment, limiting the amount of ethanol that can be produced by a given ethanol facility. We therefore have developed a small-scale prototype system that very precisely removes the hulls from barley kernels and produces two fractions. One fraction contains the starch-containing parts of the kernel, which are ideal for producing ethanol. The other fraction contains non-fermentable fibrous components that can now be sold as animal feeds or fuel pellets. The process uses a type of mill developed for grinding grain into small pieces but by modifying the way the mill is used and the direction of the blades, the process just strips away the hull, leaving the rest of the kernel untouched, and ready to go into a barley fuel ethanol plant. Use of this dehulled barley in an ethanol facility will increase its efficiency and throughput. This information will be of value to those currently building barley ethanol plants and to those who design milling systems for barley’s use in fuel ethanol, food, or feed production.
Technical Abstract: The objective of the study was to explore an alternative use of the Fitzpatrick Comminuting Machine: to use it to remove the hull from hulled barley while keeping the barley kernel intact. Traditionally, this mill is used to grind material, but we have recently discovered that it also has the ability to precisely shear the hull from the kernels using the sharp end of the blades. Different residence times in the mill were compared, and chemical analysis of hull and kernel fractions, as well as rates of hull removal, were studied to determine optimal settings. While whole kernels had only 59% starch content, dehulled barley kernel fractions had starch contents of over 71%, which are comparable to high-starch grains, such as corn, which are more efficient for fuel ethanol production. Furthermore, corresponding hull fractions had minimal starch loss of less than 6%. With initial kernels having 59% starch content, the "Fitz" mill has made a significant improvement to the barley’s value as a feedstock for fuel ethanol production, increasing the starch content by 12%, and simultaneously, decreasing non-fermentable fractions by a similar level. With a method to convert hulled barley into starch enriched kernels and fiber rich hulls, hulled barley becomes a more desirable feedstock for fuel ethanol production. The hull can then become an additional byproduct which can be used for extraction of valuable coproducts, as a feedstock for cellulosic ethanol, for use in ruminant feeds, or as a combustion fuel at an ethanol plant to produce heat and power at the facility and lower the fossil greenhouse gas emissions at the plant. While the throughput of this mill is suitable only for laboratory-scale studies, the principles elucidated may be useful for designing high-throughput continuous dehulling equipment for barley ethanol plants now being built in the US and abroad.