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Granular Packing Influences Bulk Density of DDGS

¹Biological Science Aid, USDA-ARS, North Central Agricultural Research Laboratory, Brookings, SD 57006. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ²Lead scientist, Bioprocess engineer, USDA-ARS, North Central Agricultural Research Laboratory, Brookings, SD 57006. ³Corresponding author. Phone: 605-693-5248. Fax: 605-693-5240. E-mail address: kurt.rosentrater@ars.usda.gov

As the quantity of ethanol produced continues to increase, the amount of distillers dried grains with solubles (DDGS), the primary coproduct of ethanol manufacturing, has become more widely available. Currently, the main consumer of DDGS is the livestock industry, but new value-added uses are garnering interest. With the increase in the availability of, and demand for DDGS, transportation has become an important issue because DDGS must be shipped increasingly long distances using railways. Rail transportation is expensive, especially considering the quantities of DDGS that can be loaded onto unit trains. DDGS often has low bulk density and poor flowability characteristics. This study examined compression effects on particle arrangements as quantified by bulk density and compressibility of the DDGS. Mean loose bulk density was 446.18 kg/m³. A linear relationship (R² = 0.982 for 50 N applied force and R² = 0.959 for 1 kN applied force) was observed between the applied stress (≈0.0–0.0065 and ≈0.0–0.13 MPa, respectively) and the resulting packed bulk density (≤470.21 and ≤555.03 kg/m³, respectively). Compressive stress increased curvilinearly (R² = 0.994 for the 50 N load and R² = 0.997 for the 1 kN load) as the applied strain increased (≈0.0–0.007% and 0.0–24.0%, respectively). As the loading increased, compressibility increased 5.11–19.22%. Bulk restitution after loading was removed was 0.53–0.61. Required storage volume is reduced when the bulk density is increased. But flowability characteristics should improve as the compressibility, and thus the bulk density, of the product is reduced.