World Grain - October 2008 - 62

BIOFUELS QUARTERLY: DDGS STORAGE
AND HANDLING CHALLENGES

automated loadout rates of a silo and can accommodate the
needs of those that believe in the curing process.
HANDLING DDGS AT FEED MILLS
While DDGS and soybean meal possess some similar flow
characteristics when stored in bulk, there is evidence suggesting that DDGS should be stored and handled differently than
soybean meal, and some caution should be exercised.
DDGS seems to have a higher cohesive strength than soybean meal, which means it is better able to stick together or
gain strength over time.
An important part of this discussion involves recent trends
being seen at feed mills. The challenges associated with handling DDGS may be aggravated by these trends, which include construction of much larger feed mills and production
expansions at existing feed mills requiring more on-site material storage. Another recent trend is the concept of receiving multi-rail car loads of meal, which also leads to increased
storage capacity requirements.
To explain how the characteristics unique to DDGS affect
the ability to successfully handle it at feed mills, you need to
look at what really happens in a storage silo. It is common
to expect initial flow when you convey the majority of grainbased meals into a storage silo. However, there are silo conditions such as the passage of time, the introduction of moisture
(either from leaks, humidity or material temperature), compaction, material densification, and cohesiveness that can lead
to restricted flow in the silo.
The material can often become "stagnant" in the corner of
silos, which is defined as the point where the cone meets the
straight wall. As time passes, more material can become stagnant in the corners and create an environment where material
does not flow freely. Eventually, a condition called "rat holing" can occur. A rat hole is where stagnant material creates a
solid ring around the silo, reducing the active diameter of the
silo. Ultimately, conditions can deteriorate to the point where
material will create a "bridge" and material flow will stop.
Two methods can be used to avoid this problem. The first is
to design a storage system that will permit the DDGS to recirculate or move frequently. The second is to invest in an aggressive reclaim system that can actively keep material from
becoming stagnant in areas of the silo.
DDGS is being effectively stored and reclaimed at many
ethanol plants and feed mills. From a material handling perspective, DDGS can be utilized much like soybean meal.
Careful consideration of storage requirements and discharge
rates is important to ensure long-term success with the hanWG
dling of DDGS.

.1 Id

Mike Schuster is vice-president of sales at Laidig Systems, Inc.,
Mishawaka, Indiana, U.S. He can be reached at mikeschuster@laidig.com.
For more information, see Page 86.
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