The growth in fuel ethanol production has dramatically increased the production of distillers dried grains with solubles (DDGS), a granular bulk product obtained from the nonfermentable residues of corn during ethanol bioprocessing using the dry grind production process. For every bushel of corn converted into ethanol — a third which constitutes the unfermentables — is dried and sold as DDGS. Since DDGS is primarily used as a feed ingredient for livestock diet rations (beef and diary cattle, swine and poultry), most plants are set up to produce the dried coproducts. Once created, they are shipped via truck or rail for use by distant customers.
In the United States limits have been placed on the proportion of DDGS used in feeding livestock, constraining growth in the domestic market. Since there is no other major value-added use of DDGS in the United States, the growing overseas market, which commands a large supply of DDGS, is important. The export market makes long-distance DDGS transport to export markets important to the ethanol industry — especially as ethanol production increases to meet the Renewable Fuels Standard II (RFS2) mandate (15 billion gallons/year of corn ethanol).
Problems in DDGS transport
Flowability of DDGS has been cited as one of the major hurdles to expanding existing markets and developing new markets for DDGS. Two Class A carriers that were allowing DDGS transport in their cars no longer accept DDGS; and exporters in the Pacific Northwest refuse to handle DDGS because of flowability issues. Ethanol plants are left with the expensive option of leasing or purchasing their own hoppers — and owning or leasing railcars presents an unnecessary financial and logistical burden.
In order help with logistics, DDGS is normally transported in super jumbo hoppers, and is estimated to use about 70% of the available fleet in the rail industry. The use of freight containers has become a popular method of shipping DDGS, but they still encounter the same flowability issues as with hopper cars — affecting their availability and cost.
Given these obstacles, the improvement of DDGS logistics — especially its flowability from railcar hoppers, transport containers and feed bins — is important to growing the industry. Additionally, finding other value-added uses for this coproduct is also an important issue that must be tackled in order to grow the market for DDGS.
Transportation challenges with low bulk density
While flowability of DDGS is one of the major issues with product marketability, the low bulk density of DDGS has been a concern as well because less weight per given hopper volume can be achieved, which impacts shipping cost.
For example, a standard railcar with about 161.4 m3 (5,700 ft3) volume will hold 62.8 metric tons of 389.3 kg/m3 DDGS compared to 80.9 metric tons of DDGS if the bulk density was up to 501.5 kg/m3. According to ASEA standards, corn with a bulk density of 720 kg/m3 will hold 116.2 metric tons of grain in the standard railcar; about 53.4 and 35.3 metric tons more than the low and high bulk density values. The higher the bulk density, the cheaper it is to transport DDGS, and expand its market. Because the bulk density of DDGS can vary from 389.3 to 501.5 kg/m3, the shipping cost for the product can be variable as well, and can even dictate how far a product is shipped and how well it handles.