Preventing
mold on wooden pallets has become increasingly more important as a growing
number of pallet users demand pallets that have been treated to prevent the
growth of mold.
If the
proper steps are not taken, wooden pallets can be a fertile breeding ground for
mold growth for several reasons.
Mold 101
“Mold
spores are everywhere,” said Dr. Brian Bond, associate professor of wood
products at Virginia Tech. “They’re in the air all the time and in almost all
environments. And wood is a good food source. Mold needs several things to
grow. It needs a food source, it needs the right temperature, it needs moisture
content, and it needs air. Wood is a good medium for that because the sugars
and starches in wood are a food source and the high moisture content in green
wood provides plenty of moisture for the survival of the fungus. And if the
temperature’s warm enough, which is pretty much over half of the year, it makes
a great environment for mold to grow on. Most pallets are produced still in the
green condition, so they are a prime source for mold growth.”
The key
to preventing mold grow is controlling one or more of these elements that mold
needs to grow. Controlling air is virtually impossible, and controlling
temperature is not easy either as the temperature range that is conducive to
mold growth is also the temperature range that is most comfortable for workers.
So that leaves moisture and food source that can be controlled.
“If
you’re going to eliminate one of those variables, reducing moisture or making
the food source unavailable through chemicals are the most viable options,”
said Bond.
Many
pallets users think that heat treating pallets helps prevent mold growth. But
in reality, heat treatment is done to kills wood pests so that export pallets
comply with ISPM-15 standard. It has little to do with prohibiting mold growth
unless the pallet is dried to less than 20% moisture content. The heat treating
process can actually make wooden pallets or lumber more susceptible to mold, by
bringing to the surface moisture and sugars that are necessary to facilitate
mold growth.
Treatment Options
Bond
pointed out that there really is not one single method of mold prevention that
is the best or most cost-effective for all pallet companies.
“There
are variables that influence that depending on the customer, use, the time
period and acceptance of the treatment method,” said Bond.
For
pallet companies that want to use a chemical treatment, companies such as ISK
Biocides and X-Mold have options available. ISK Biocides offers two fungicide
products that it recommends for mold prevention on pallets – PQ-80 and NeXgen.
Both can be applied by dipping or spraying assembled pallets or components
prior to assembly. PQ-80 may also be applied by electrostatic deposition.
Though
chemical treatment of pallets is not government-regulated, some pallet
customers, especially those in the food and pharmaceutical industries, may
require that any chemical mold treatment be government approved. The active
ingredients of NeXgen are registered with the Food and Drug Administration
(FDA) and Environmental Protection Agency (EPA) for control of fungi on more
than 50 vegetable and fruit crops and for use in materials which may come into
contact with foods. The active ingredient in PQ-80 is allowed by the FDA as a
preservative for wooden articles used in transporting, packaging or holding
agricultural products.
More
information on PQ-80 or NeXgen is available by calling 800/238-2523.
X-Mold’s
chemical treatment, E-Fusion, is a protective coating that is applied with an
electrostatic spray booth. According to the company, the coating bonds to wood
almost instantly when applied using its proprietary electrostatic spraying
technology, creating a protective coat that is not water-soluble and will
therefore not wash off. All ingredients in the treatment are EPA registered and
approved and registered with the National Science Foundation (NSF) to be used
as a coating on wood pallets transporting packaged goods in and around food
processing areas, according to X-Mold. More information on
E-Fusion is available at http://www.xmold.net/
One
thing to keep in mind with chemical treatments, is that they are usually
“envelope treatments” – meaning they only treat the surface of the product. So
if any cuts are made after the treatment, that “envelope” is opened, meaning
that the product would need to be re-treated.
If
chemical treatments do not seem like the right fit for a pallet operation,
drying the pallets may be. Drying for mold prevention is different than heat
treating a pallet. Heat treating gets pallets hot, but it does not dry them, as
heat treatment standards are not designed for mold prevention. According to
Bond, a moisture content below 20% is usually sufficient to prevent mold growth
on pallets, and heat treating according to ISPM-15 schedules will not reduce
moisture content to this level.
“There
are treatment chambers that have the ability to dry after treatment, but it’s
not the standard practice,” said Bond.
For
pallet companies interested in drying pallets, there are options offered by
companies such as Lumber Sales & Products and Big Ass Fans. Lumber Sales
& Products has a relatively new product in its Air-Flow Trailer System
(AFTS) which is a design for trailers that combines two strategically placed
heavy-duty fans and 14 vents to create air flow through a trailer and control
moisture in the trailer.
“Every
30 seconds there’s fresh air circulating through the trailer,” said Jim
Francois, president of Lumber Sales & Products. “All you’ve got to do is
load up a semi-trailer and plug in the fans. It’s very simple.”
Depending
on the weather, pallets in a trailer will dry down to 19% moisture content
within four to five days, Francois said. Other benefits of AFTS is that it can
be used as a fan shed, reduces handling of pallets as they can be loaded once
for drying, storage and delivery, and can also prevent mold in the trailer
itself. AFTS can be purchased as a kit that pallet companies can self-install
in existing trailers, be installed by Lumber Sales & Products, or be purchased
as a complete trailer and system. More info on AFTS is available at
http://www.aftstrailers.com or by calling 262-677-9033.
Big Ass
Fans has a similar concept. It designs high-volume, low-speed fans that keep
air moving within a warehouse, preventing the buildup of moisture on surfaces
that might harbor mold by continually disturbing the thin sheet of stagnant air
surrounding each pallet. These large-diameter, low-speed fans use their immense
size—not speed—to move a massive amount of air using very little energy.
According to Big Ass Fans, the fans are an efficient way to incorporate air
movement to large spaces with high ceilings and can easily be added as a
retrofit to existing facilities. More information on Big Ass Fans is available
at http://www.bigassfans.com.
A
common misconception among some pallet users is that once a pallet has been
treated, it will be mold-free forever.
“How
you treat the pallet after a preventative treatment method is equally important
to preventing mold growth for future use,” said Bond. “Any preventative
treatment is not a lifetime treatment. Any preventative treatment is just a
treatment that is going to last for as long as that pallet is kept at those
conditions throughout storage, transfer and use.”
The
best way to avoid mold on pallets is to choose a treatment that works well with
your process and your customers’ needs. Bond said that to effectively prevent
mold growth, everyone in the supply chain must be involved in the prevention.
“The
producer’s got to be aware, treat it right, get that pallet to the user in the
right condition,” said Bond. “But the user can’t assume that it’s a lifetime
treatment. They have to also respect the fact that if you expose it to the
wrong conditions – i.e., leave a dry pallet out in the pouring rain – it’s
going to pick up moisture.”
