World Grain - February 2018 - 62

GRAIN OPERATIONS

Silo bags as a storage option
Hermetically-sealed bags offer an economical,
flexible and safe method to store grain
by Dirk Maier

For the global food system to keep up, more food grain must
be produced and less must be lost post-harvest and wasted
before consumption. Hermetic storage is an ancient technology used to control insect infestation in grain and preserve its
nutrient quality and caloric value.
In ancient times, agricultural societies stored their surplus
grain in containers or structures that kept it safe from the elements and restricted the entry of rodents, birds and insects.
Well-sealed structures also prevent air exchange between the
inside and outside of the storage space. By preventing air ingress to the grain, the aerobic respiration of grain, and, if present, insects and fungi, decreases O2 and increases CO2 in the
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atmosphere. It has been shown that CO2 generated from aerobic respiration alone does not increase to levels high enough
to kill insects; instead, it is the lower O2 level that is the key
factor in halting insect development.
In large-scale hermetic storage, it may take weeks or
months for O2 levels to decrease by respiration to levels lethal
to stored product insects (below 4% to 5%), especially when
infestation is low. As a result, practical commodity managePHQWPD\UHTXLUHVXSSOHPHQWLQJELRPRGL¿HGKHUPHWLFVWRUage with additional control methods such as adding CO2 or
nitrogen injection or fumigation with phosphine or sulfurylÀXRULGH
Historically, cereal grains were stored hermetically in underground pits lined with clay or in small containers such as
gourds or clay pots, but today technology exists that allows
large quantities of grain to be stored hermetically. Large bulk
silos and warehouses for both bulk and bag storage have been
sealed to a high degree, most notably in Australia.
Making large structures completely gastight is a challenging and costly undertaking. In permanent structures, allowing
for a small amount of air exchange between the interior and
exterior of the structure (i.e., pressure venting) is a practical necessity because of potential structural damage due to
62

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hermeticity) standards have been extensively researched, and
the half-life pressure decay test remains the simplest and most
effective test to quantify hermeticity.
Hermetic storage has been accomplished successfully on
ODUJHVFDOHVLQWKHIRUPRIXQGHUJURXQGSLWVFRYHUHGZLWKÀH[ible roofs in Cyprus and Argentina, sealed commercial silos in
Australia, sealed warehouses for bulk grain in China, hermetic
bunker storage in Israel, and grain bag stacks enclosed within
gastight liners (cocoons) in several African countries.
SILO BAGS
For medium-scale grain storage, silo (or grain) bags that originally were developed for anaerobic storage of chopped forages,
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early 2000s and from there adopted into many countries around
the world. Silo bags utilize a time-tested method (i.e., hermetic

Hermetic storage is an ancient
technology used to control
insect infestation in grain and
preserve its nutrient quality
and caloric value.
storage) and incorporate modern technology to provide producHUVDQGFRPPHUFLDOJUDLQPDQDJHUVZLWKDQHFRQRPLFDOÀH[ible and safe method to store grain, especially during times of
record harvests, bumper stocks and low grain prices.
Research conducted in Argentina by Bartosik et al. (2008)
proves that silo bags are a viable technology for a range of
crops. For the past several years nearly half of the grain (40
million to 50 million tonnes) produced in Argentina has been
February 2018 / World Grain / www.World-Grain.com
http://www.World-Grain.com
World Grain - February 2018

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