Moisture content has a significant impact on pallets and lumber. Quite simply, what you don’t know can hurt your products. Brian Bond, professor and extension specialist at Virginia Tech, has dedicated his time to educate students and the industry about best practices for lumber drying and pallet treatment. Bond shares some insights on technology as well as the current state of drying and heat treatment practices.
Bond said, “I haven’t received many calls from heat treaters in quite a while. The issue that still comes up the most is mold. There still seems to be a lot of confusion about what causes mold in packaging in pallet material from the end users.”
Customers think that just because something is heat treated that it won’t foster mold growth. But that is not necessarily true. Actually, heat treatment may encourage mold growth if moisture is brought to the surface and pallets are improperly stored.
Bond explained that heat treatment is about killing invasive insects and pathogens in wood not removing moisture and drying the material. That is particularly true for hardwoods, which tend to take longer to dry than softwoods. Although with softwoods, drying and heat treatment often takes place at the same time.
Bond stated, “With hardwoods, you’re not typically drying it at the same time you heat treat because it takes so long to dry hardwoods. Whereas with southern pine, you can dry it so rapidly using high temperatures that you can heat treat and dry at the same time. Also, the markets for the two wood materials are quite different.”
These factors have led to the rise of softwoods used for pallet production because they can be easily dried to reduce moisture content and mitigate some mold issues. Generally, in the heat treatment process for hardwoods, you don’t want to dry the lumber because you lose BTUs to evaporation and rapid drying leads to significant degrade.
Concerns over mold have even led to lawsuits due to damage product when green lumber was used for pallet production. That’s why the pallet provider and pallet user need to communicate to ensure that the right type of lumber is used for each application.
Looking at developments in drying technology, Bond pointed to the rise in popularity of continuous kilns. He said, “Although continuous kilns have been around for a little while, they are gaining in popularity with recent design changes, which improve quality and drying times. A classic example in Virginia would be Morgan Lumber put one in and that’s an existing operation, but they were looking to expand production.”
Explaining the differences between continuous and conventional drying, Bond said, “In the continuous approach you have lumber going through stages versus the batch drying process in one chamber. This leads to some cross conditioning that has a faster throughput. These systems do require more land to facilitate. But pines producers seem to really like them.”
Experts like Bond at major research universities stand ready to help the industry adapt to changing situations, such as drying new species of wood or evaluating new technology. Recently, Virginia Tech has been working to develop vacuum-steam process for phytosanitation of export logs. The vacuum-steam process has been suggested as possible replacement for methyl bromide fumigation.
Some of the major universities with wood or forest product programs include: Virginia Tech, Oregon State, Mississippi State, NC State and others. Bond explained, “As an extension specialist, I help companies in my state troubleshoot issues and develop strategies for process improvements. When it comes to specific applications, experts like myself are also available for consultation on specific projects unique to a company.”
Editor’s Note: Brian Bond, PhD, is a professor and extension specialist at Virginia Tech. He is a recognized expert on lumber drying and related wood treatment. For more information or to contact him with a specific question, please call (540) 231-8752 or email bbond@vt.edu.
