Stillage, which is formed during the distillation of grain into ethyl alcohol, contains many proteins, fiber, carbohydrates and micronutrients. For this reason, it is used as a raw material for the production of cattle feed. However, Kentucky’s cattle population is at its lowest since 1962, whereas bourbon production is expected to double in the next five years. An alternative could be the use of stillage to generate electricity.
In order to obtain electricity, the UKY scientists used anaerobic digestion technology, which comprises two main stages. First, organic matter is placed in an oxygen-free reactor, where it is broken down into alcohols, fatty acids and ammonia under high temperatures. Then, methane-forming bacteria help convert these components into a mixture of methane and carbon dioxide, which can be used to generate electricity via a conventional combined-cycle unit. The authors of the study also found that CH4 and CO2 content can be varied depending on the type of grain from which stillage is obtained (corn, wheat or barley).
The anaerobic digestion technology is already well-known in the power industry. It was first tested at the Enerbio power plant with a capacity of 1 MW, which was launched in northern Italy in 2012 and uses corn silage as raw material. The same technology will be used in the city of Kasaoka in southern Japan, where a 1.2 MW power plant is being built. The plant will process waste from local livestock farms into biogas for subsequent power generation. Finally, the most famous example is the project of Spain’s Emasesa, which built a plant in Seville several years ago to generate electricity from an inedible variety of oranges.
