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Research looks at issues surrounding flowability of DDGs Tuesday, February 20, 2007
By Lee Johnston
The ethanol industry is expanding rapidly. Large quantities of distillers dried grains with soluble, a co-product from the manufacture of ethanol, are available for feeding livestock.
Unfortunately, DDGs can have some undesirable handling characteristics related to poor flowability under certain conditions. Reduced flowability and bridging of DDGs in bulk storage containers and transport vehicles limits the use of DDGs in feeding livestock.
Few attempts to characterize factors affecting flowability of DDGs have been reported in controlled studies. Calcium carbonate is added routinely to soybean meal to improve flow.
We theorized that addition of flow agents to DDGs might improve flowability. Realizing the importance of handling challenges presented by DDGs and the lack of controlled studies under commercial conditions, our swine research group at the University of Minnesota designed a study to determine if the addition of selected flowability agents is effective in improving flowability in practical commercial conditions. Our study was conducted at the BushMills Ethanol plant in Atwater, Minn. The experiment had four treatments to examine effects of flowability agents added to DDGs. Treatments included: A control that received no flowability agent; 5 pounds per ton of DMX-7 supplied by Delst, Inc.; 2 percent calcium carbonate supplied by ILC Resources; or 1.25 percent of a clinoptilolite zeolite provided by St. Cloud Mining in New Mexico.
Each of these flowability agents were mixed into 5,000 pound lots of DDGs that contained either 9 percent moisture or 12 percent moisture. Therefore, we had eight total treatments (four flowability agent treatments applied to DDGs of two different moisture levels).
Once the lots of DDGs were prepared, we loaded each one into a separate compartment of a commercial feed truck. The truck traveled about 150 miles, sat idle for two days, then traveled 150 miles back to the ethanol plant. Upon returning to the ethanol plant, we recorded the time required to unload each compartment of the truck. This time in combination with the known weight of DDGs loaded in the compartment allowed us to calculate a flow rate (pounds/minute) for each treatment.
This procedure was repeated four days.The first thing we noticed quite convincingly in the data was that drying DDGs to 9 percent moisture greatly improved flowability compared to 12 percent moisture. The drier product unloaded at 1,368 pounds/minute while the wetter DDGs flowed at 859 pounds/minute. We expected this result from our previous experiences and reports from the feed industry.
However, it was important to quantify the magnitude of the moisture effect. More importantly, we wanted to know if the flowability agents we tested would be more or less effective in DDGs of differing moisture content.We found that none of the flowability agents we tested significantly improved the flow rate of DDGs compared with the control treatment that included no additive. The effect of flowability agents was similar for DDGs with 9 percent or 12 percent moisture. Flow rate for the control treatment was 1,123 pounds/minute while flow rates for the treatments with flowability agents ranged from 973 pounds to 1,229 pounds/minute. While there appeared to be differences in flow rate, our statistical analysis of the data suggested these differences weren't consistently repeatable.
From this study, we concluded that moisture level of DDGs plays a very important role in determining the flowability of the final product. Addition of the flowability agents at the levels we studied provided little evidence for improved flowability of DDGs. An additional aspect of our study yet to be completed is to determine characteristics of DDGs that might predict poor flow rates before they create problems in commercial systems. By evaluating and determining the main factors involved with flowability of DDGs, we hope to be able to explain differences in flowability observed from different DDGs sources, and aid ethanol plants in improving the handling characteristics of DDGs produced.
Lee Johnston, professor and swine Extension specialist at the West Central Research and Outreach Center, Morris. |
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