Pallet users are more concerned than ever about moldy pallets. Proper handling
and the right components and materials can go a long way to preventing mold. Experts at
the NWPCA and the Department of Wood Science and Forest Products at
Virginia Tech argue that the real issue is how pallets are stored and handled prior to
shipment and not whether they are treated with chemicals.
The reason is that mold occurs naturally and is present everywhere. That’s why mold will
grow on a piece of bread left too long in an otherwise clean refrigerator. By the same
token, mold will grow on pallets constructed from kiln-dried lumber or even plastic
pallets if they get wet and are then stored in a warm, damp environment. For that reason,
storing a load of pallets in an enclosed trailer, especially during the warm months of the
year, creates ideal conditions for growing mold, even if the pallets are relatively dry.
Similarly, some of the antidotes for killing mold can actually encourage its growth later.
Heat treating a pallet to kill insects and insect larvae will kill mold in the
short run. But the process is not designed to dry a pallet. Instead, research at Virginia
Tech found, the process brings moisture to the surface of the wood which can induce
mold growth at a later date if the pallet isn’t properly handled.
What’s the simplest way to control mold? Here are a couple simple steps. First, avoid storing
pallets in the yard or in an enclosed trailer for an extended period of time. If the pallets are
washed down or get wet for any reason, make sure they are dry before putting them back
to work. Second, know where your pallets are going to be shipped and how they are going to be
used. In most climates, a green hardwood pallet will work fine if it’s been properly stored.
However, in humid environments, or in situations where palletized product will stay in an
enclosed trailer or container for an extended period of time, research has shown that
chemical treatments are an effective way to prevent mold. Since many shippers are
reluctant to use chemically-treated pallets, a pallet dried to an average 20% moisture
content is less likely to provide the conditions to grow mold.
Brian Bond, Case Studies of Heat Treating and Mold Control of Wood Pallets,
Peter Hamner and Marshall White, Mold, Mildew on Pallets, Lumber Can Be Prevented,
Eliminated, Pallet Enterprise
Matthew Harrison, Mold, Fungi Still Pose Threats to Pallet Businesses, Pallet Enterprise,
Dealing With Moldy Pallets, Modern Materials Handling,