Ever since the ethanol industry began marketing distillers' dried grains with solubles (DDGS), it has struggled with variance in the byproduct's nutrient content. DDGS are the portions of grains that can't be broken down into sugars used for ethanol, and they are often sold as a feedstock for livestock. However, DDGS often consist of varying levels of fiber, protein, sugar and amino acids.
"If every time you get a batch [of DDGS] it's different from the last, you are uncertain of the nutrient value you're giving your animals,” says Klein Ileleji, Purdue University assistant professor of agricultural and biological engineering. "What you want is a consistent product.”
Ileleji may have found a way to predict the nutrient content of DDGS. The solution lies in the balance of the liquid and solids, he says. The ethanol production process leaves behind solids that can't be converted into sugars, and the liquid is centrifuged to remove excess water and create a syrup. The solids and liquid are mixed to create DDGS.
A difference in the ratio of grains and syrup will change the nutrient profile, Ileleji says. For instance, increasing the syrup in the mix leads to a decrease in fiber and protein but an increase in the amount of residual sugars.
"Ethanol plants don't blend these streams of solids and syrup in a uniform manner,” explains Ileleji, whose research results are published in the early online version of the journal
Bioresource Technology. "The jumping around of these different properties comes from different blending processes.”
Ileleji is creating a model based on this study's data that will allow ethanol producers to blend DDGS to give specific nutrient profiles.