World Grain - October 2008 - 59

BIOFUELS QUARTERLY

DDGS

storage and
handling challenges
W

hen comparing two grain-based ethanol byproducts, wet distillers' grains and dried distillers
grains (DDGS), there are striking differences when
it comes to storage issues.
Wet distillers' grains typically have a moisture content of
65%. They don't require drying, which means tremendous energy savings for the producer, and they are also a preferred
feed for livestock.
However, wet distillers' grains have a very short shelf life
and are very corrosive, which has a detrimental effect on material handling equipment. Stainless steel is typically required
for equipment that will convey the wet distillers' grains.
If wet distillers' grains are produced, they are commonly conveyed to a flat storage pad outside the drier building. Since they
are typically transported by trucks, front end loaders are used to
scoop the material from the pad to the open top trailer.
Meanwhile, DDGS, which has moisture content in the
range of 10% to 11%, can be effectively stored and reclaimed,
which provides transportation options and flexibility. DDGS
is much easier to convey than wet distillers' grains, maintains
feed quality longer, and offers the potential of being produced
in pellet form.
Perhaps the only disadvantage linked with the production
of DDGS is the significant energy cost associated with the
driers.
Many ethanol plant operators believe DDGS must sit in an
open pile for a length of time to "cure" or "temper," a process that ranges from 24 to 48 hours. The idea behind curing
DDGS is that the material can be conveyed, stored and transported more easily after this process. It is an attempt to address the issues of heat dissipation or any chemical reactions
following the production and drying of DDGS. Plant owners
who choose to include the curing process need to account for
it in the layout and design of their facilities.
There are several facility and transportation issues to con60

by Mike Schuster

Careful consideration of storage
requirements and discharge rates
can help ensure long-term success
in handling ethanol by-product
sider when designing the DDGS storage and handling system
at an ethanol plant. One involves the size of the production
capabilities of the ethanol plant, since DDGS production is
directly linked to the amount of ethanol produced. Another
consideration involves the percentage of wet distillers' grains
that will be produced versus DDGS. This decision is typically
influenced by the availability of a local market for the wet
product, which cannot be shipped long distances because of
its short shelf life.
While most ethanol plants load trucks, many are now being
built with substantial rail facilities, and there are also plants
that can load product onto ships. The available forms of transportation can dictate loadout capacity for DDGS. If a plant
cannot load out fast enough, it may be forced to pay demurrage charges for the extra time required.
Transportation issues may also affect the amount of DDGS
storage that will be required at the plant. For example, if a
plant intends to load 75- or 100-car trains, then adequate storage and fast reclaim systems must be included in the plant
layout. The majority of ethanol plants have approximately 10
days of DDGS storage.
THREE BASIC CONCEPTS
There are three basic material storage and handling conOctober 2008 / World Grain / www.World-Grain.com

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World Grain - October 2008

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