As the weather warms, mold becomes an even worse problem for pallet suppliers. Proper treatment of lumber or pallets and storage conditions can do a lot to reduce the mold threat.
Mold on pallets can be serious business. In recent years, Starbucks went after a company that supplied it with wood pallets that were used to ship and store coffee beans. Starbucks claimed that mold on the pallets contaminated several million dollars’ worth of coffee beans that had to be destroyed, and the company initiated a $5.3 million lawsuit in federal court against its pallet supplier. Also, Johnson & Johnson and Pfizer recalled product that had developed a noxious odor. Both companies pointed to wooden pallets shipped from Puerto Rico. In both cases, the cause was linked to a chemical treatment applied to wood in order to prevent mold.
Mold spores are everywhere. If they have enough oxygen, moisture, the right temperature, and a food source, they can germinate in 24-48 hours. Wood is a food source for mold. Since mold can occur in a fairly broad temperature range, moisture content of wood becomes a controlling factor to prevent mold. Another option is to treat the wood with a product that prevents or inhibits mold growth.
Mold needs four things to grow — oxygen, food, water or the right temperature. A successful mold control program will usually involve a combination of strategies aimed at eliminating or reducing one or more requirements for mold growth.
Experts agree that the key to controlling or preventing mold growth on wood is the moisture content. If the moisture content is below 20%, wood will not support mold, mildew, decay, or fungus, according to the Virginia Tech Center for Packaging and Unit Load Design.
However, even wood dried to that level does not guarantee that mold will not occur. If the right conditions exist, some remaining moisture in the wood can come to the surface, and if it accumulates, mold can occur. Also, even if the wood is dry, mold can occur if the wood becomes wet from some other source, such as rain.
You may need to dip lumber, pallet cut stock or pallets in a fungicide. While dipping in a fungicide is not a magic bullet, it can buy time to prevent mold on pallets until the wood is dry. Fungicides are effective at preventing mold. However, they do not work nearly as well if mold already exists on wood before it is treated.
Tips for Preventing Mold on Wood
There is no single thing you can do to absolutely prevent mold, but there are a lot of little things you can do to reduce the likelihood that mold occurs on lumber or pallets.
Keep lumber and pallets away from any sources of mold spores, such as decaying wood. Simple good housekeeping practices can reduce the presence of mold spores in the air. Use freshly sawn wood that has not been stored for a long period of time. The longer the lumber or material is stored, the higher the risk it will develop mold.
One of the most important strategies is improving air flow to aid in drying the wood. This should occur throughout the process from the sawmill to finished pallet production and storage. Improving air flow and hastening the drying process can help prevent mold.
Incorporate practices and procedures to enhance drying. Store lumber and pallets in areas that are well ventilated. Trailers should be unloaded quickly, and wood should be stored taking into account spacing and arranging in order to maximize air flow. If pallets or material are stored in a warehouse, use fans to generate air flow and make sure the building is dry. Even slight air velocity of a few feet per second can help prevent mold.
If pallets are heat-treated, they should be unloaded immediately after the treatment cycle is completed. Allow them to cool before they are loaded into trailer vans. Heat-treated pallets that are loaded into trailer vans while still hot are susceptible to mold. In fact, the heat-treatment process pulls out internal moisture to the surface of the wood, which can actually lead to more favorable conditions that allow mold to occur.
Note: heat-treating is designed to kill insects. It may kill existing mold spores on the surface of wood, but the heat-treating process does not prevent mold spores from growing. Wood that has been heat-treated is not immune to mold.
Even with heat-treated lumber or pallets, create good air flow to allow the surface of the wood to dry.
Pallets or lumber stored outside should be covered to prevent exposure to rain and elevated above the ground. Air flow is critical too for outdoor storage sheds.
Another option is to treat the wood with chemicals that protect the wood and prevent mold from growing. Generally, dipping lumber or pallet components in fungicide is more efficient than dipping finished pallets because a larger volume of wood can be treated more quickly. Spraying fungicide can work, but it is more difficult to get consistent treatment.
For pallet applications where chemical exposure is less of a concern, the Virginia Tech Center for Packaging and Unit Load Design recommends periodically applying a bleach solution to the lumber.
Another option to kill or remove mold is to spray or dip the pallet or lumber in a solution of two parts water and one part of a household detergent. The solution will be effective for 3-5 days.
Kiln-dried lumber may be an option. Wood that has been dried to less than 20% moisture content will not support mold growth, and kiln-dried lumber is below that level. However, kiln-dried lumber can quickly grow mold if it becomes wet.
After pallets have been delivered to a customer, the battle against mold may not be over. Do not drop off trailers of pallets that your customer uses for storage; a closed trailer is an incubator for mold. Also, educate your customer about ways to store and handle pallets in order to prevent mold from occurring.
Supplier Treatment Solutions
ISK Biocides Offers a Full Range of Mold Control Treatments
ISK Biocides, based in Tennessee, is a leading supplier of chemical products for wood for residential, commercial and industrial applications.
The company offers several products to treat pallets, but there are differences among them, noted Lance Johnson, vice president of sales and marketing. He normally recommends PQ-8 or PQ-80 for pallets because they are approved by the federal Food and Drug Administration for incidental contact with food. The company’s NeXgen® fungicide does not have that approval, but it has two active ingredients instead of one, making it the strongest of the products and effective for a longer period of time. PQ-8 and PQ-80 combined are the company’s best-selling products for treating pallets.
PQ-8 and PQ-80 vary mainly by the percentage of their active ingredient although both are effective for the same length of time. One difference is that PQ-8 meets U.S. military specifications for preservatives for pallets and wooden crates and boxes. PQ-8 also is a thinner concentrate, which makes it easier to pump in cold weather.
NeXgen brightens wood while also controlling sapstain and mold fungi. It combines two chemicals that work to quickly penetrate and bind to wood, minimizing leaching while effectively protecting the wood from mold and sapstain fungi. It is recommended for green lumber but can also be used on dry or partially-seasoned wood to prevent stain and mold.
How long any of the fungicides are effective depends on numerous factors, Lance explained. Those factors include the dilution rate of the product when mixed with water, the species of wood, and the conditions under which the pallets or lumber are stored.
For more information about ISK Biocides products, call (800) 238-2523, email info@iskbiocides.com, or visit www.iskbiocides.com.
Pallet Machinery Group Offers WoodLock Bio-Shield™
Pallet Machinery Group listened to their customers and is offering an environmentally friendly, safe mold inhibitor called WoodLock Bio-Shield™. This new product is highly effective at preventing mold on wooden pallets and sawn wood.
WoodLock Bio-Shield was developed by Jim Stanley, who has lengthy experience in the coatings industry. Stanley designed a chemical product to treat homes to inhibit mold growth and has reformulated the product to use on lumber and pallets.
WoodLock Bio-Shield inhibits mold growth by stopping the gestation of mold spores. It is formulated with a proprietary polymer that bonds with the anti-microbial and mechanically bonds to the wood.
WoodLock Bio-Shield is not water soluble, so it is effective despite repeated dry-wet cycles. The active ingredients are on the EPA Safer Alternative List, and WoodLock Bioshield has been tested by Louisiana State University and Virginia Tech using AWPA E24-16 Laboratory Method for Evaluating the Mold Resistance of Wood-based Materials. This mold chamber test showed no mold growth after six weeks, which is the equivalent to three to four months in a real world environment.
The active ingredients of WoodLock Bio-Shield are bio-available at just 10% humidity. WoodLock Bio-Shield has a higher availability at a higher humidity. The active ingredients are captive on the surface of the wood; then, when moisture is present, the film softens and becomes more bio-available, preventing heavy mold growth. The polymer seals as it dries so it can work repeatedly.
WoodLock Bio-Shield’s active ingredient is listed on the EPA’s Safer Alternative List, and it is currently pending certification for indirect food and pharmaceutical contact on wooden pallets. The active ingredients, which are registered with the EPA, are non-caustic, benign and will not leach into the environment.
For more information, call Pallet Machinery Group at (540) 644-9220 or visit www.palletmachinery.com.
Mold Needs Four Things to Grow
1. Oxygen
Oxygen is in the air all around us and cannot be eliminated.
2. Food
Wood provides nutrients for mold to grow.
3. Temperature
Generally, temperature cannot be controlled since most pallets are stored in ambient conditions. Mold can grow in temperatures as low as 32 degrees. Growth is accelerated when temperatures are in the 66-90-degree range.
4. Water
Wood that has been dried to a moisture content below 20 percent will not support mold growth. However, kiln-dried lumber can quickly grow mold if it becomes wet.
