In the wood pallet industry, “mold” is a small word that can mean big trouble for suppliers and customers alike. The problem of mold is varied and diverse, and has naturally given rise to a wide array of approaches for combating it, each with its own advantages and drawbacks. Avoiding the growth of mold on wooden pallets is not a one-size-fits-all proposition, with the needs of the customer and the realities of wood production shaping the strategies used.
As with any adversary, to combat mold first requires understanding it. The term “mold” encompasses thousands of species of fungus spread by airborne spores which settle on a surface in search of nutrients to feed on. In the case of wood, the food source for mold may be detritus such as pollen and dust coating its surface, or the sugars and proteins stored within the wood, or even the structural polymers that give wood its useful properties.
Most types of mold will not compromise the physical structure of the wood, but they may create discoloration or staining. The greater problem is that, once mold has permeated a piece of wood, brushing or scraping away the visible mold will not render the wood mold-free; the mold fungus is living in the spaces between the plant cells in the wood, and will continue to produce spores on the surface whenever conditions are suitable. These spores, the reproductive cells of the mold, will seek to spread not only to other nearby wood, but other compatible materials. Wood pallet users also face concerns regarding the health effects of mold. Like any airborne particulate matter, mold spores can be a hazard for people with asthma. Also, while the types of mold infamous for producing toxins harmful to humans tend not to flourish on wood, there are susceptible individuals within the population for whom no level of exposure is entirely safe. While the primary risk of mold to wood pallet users remains the contamination of products being transported, there are numerous reasons for pallet users to want to avoid mold contamination.
How can contamination by mold be prevented?
Mold requires four conditions in order to thrive:
- Favorable temperature range
- Access to nutrients
Controlling the exposure of wood pallets to oxygen is impractical for obvious reasons, as is keeping pallets out of the hospitable temperature range for mold, particularly as some species can thrive even in colder conditions. As such, the two most viable strategies for mold prevention are rendering the nutrients in the wood inaccessible to the mold fungus, and keeping the pallets dry.
Unfortunately, many pallets are built using “green” wood, which still contains the moisture it possessed as part of a living tree. With time the wood will dry out, but until that occurs, the pallet remains susceptible to contamination by mold. Even wood that has dried, whether through age or by kiln drying, can be attacked by mold if it comes in contact with water, as is almost inevitable for pallets used or stored outdoors. The presence of free water need not be prolonged in order to create a mold problem, as the life cycle of many mold spores is completed in a matter of days. Some pallet producers use heat treatment (a different process from kiln drying) to protect against mold, but heat treatment generally only penetrates the surface level of the wood, and does not fully dry it, ironically rendering the wood an ideal host for new mold contamination.
A variety of chemical fungicides exist that can prevent mold contamination for three to six months, if applied shortly after the wood is sawn. Several chemicals are often used in combination, as each provides protection against a handful of species. While the effective concentrations of these fungicides are generally low (in the 5-10 parts-per-million range), many pallet users are concerned about chemical contamination of their goods, and require pallets without chemical treatment. Some progress has been made in the use of food-grade plant extracts, such as cinnamon leaf oil, to discourage fungal growth. The problem with these extracts is that they require a medium of ethanol for dispersion, which poses a major fire hazard for sawmills.
When chemical fungicides are not an option, the only recourse for combating mold is to fight moisture. From the customer’s perspective, this means storing pallets in dry areas. For the pallet manufacturer, it means sourcing reliably fresh wood and being careful with wood storage: avoid storing green lumber for long periods, and ensure that heat-treated wood is stored in areas with good air flow to allow surface drying. Immediately discard materials with visible mold to reduce the opportunity for contamination of clean wood.
Greenway Products & Services, LLC is the largest pallet re-manufacturer and recyclers in NY, NJ, PA, MD, and DE. We also accept scrap wood from our customers that we turn into valuable resources. Greenway is a highly-rated, full-service pallet management company. Contact us for a quote today at firstname.lastname@example.org. Visit our website, greenwaypsllc.com or call us at 732-442-0200. We can deliver trailers to you on a moment’s notice throughout the NY-NJ-PA-MD-DE area.