By Peter Hamner and Marshall White. July 18, 2008 OVERVIEW. Why is mold growing on pallets a problem?

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1 College of Natural Resources Center for Unit Load Design Wood Science & Forest Products Brooks Center (0503), 1650 Ramble Road Blacksburg, Virginia / Fax: 540/ The performance and effectiveness of X-M Industries, Inc. E-FUSION-RTU chemical fungicide in preventing mold from occurring on green (wet) wood pallet components Why is mold growing on pallets a problem? By Peter Hamner and Marshall White July 18, 2008 OVERVIEW There are many different species of molds that can grow on and contaminate wood surfaces. Mold fungi are neither plants nor animals. They are microscopic organisms that contain enzymes for digesting and decomposing organic matter, and spores used for reproduction. Although closely related, molds are different from wood rotting fungi in that they do not affect the structural integrity of wood. Mold is considered a problem for pallet manufacturers and their users because airborne mold spores are considered a health hazard. In the case of food products that are stored on moldy pallets, United States regulatory agencies (FDA, USDA) may take action when, food has been manufactured under such conditions that it is unfit for food, and when food has been prepared, packed, or held under unsanitary conditions whereby it may have become contaminated with filth, or whereby it may have been rendered injurious to health. In addition to causing health concerns, mold spores that settle and grow on wood surfaces produce an unsightly dark discoloration that persists even after the wood has dried. When does mold occur Mold spores are everywhere in the air and floating onto wood and other surfaces. Under optimal conditions, these spores will germinate within 24 to 48 hours. Optimal conditions include wood surfaces above 20 percent moisture content, air temperatures from 60 to 90 o F, dark or dim light, and little to no air movement. Mold problems on wood pallets are most commonly associated with the spring and summer seasons of temperate climates. Nevertheless, mold spores can still germinate and grow during colder weather when pallets are stored indoors with poor ventilation and at temperatures above freezing. Invent the Future

2 Industry accepted measures to prevent mold from growing on wood surfaces include: Drying: Dry pallets to less than 20 percent surface moisture content, and maintain this level throughout the shipping and storage process. Because there is a moisture gradient across the thickness of wood pallet components, achieving an average moisture content of less than 25% is usually sufficient to control mold spore germination and growth. Both kiln drying and air drying methods can be used. It is important to kill mold spores present before drying, and provide accelerated drying rates to prevent germination before, during, and after the moisture reduction process. Kiln drying is one effective method of achieving these goals together, since kiln drying will both kill mold spores and dry the wood. Kiln drying pallet parts usually takes several days to one week. For hardwoods the cost to kiln dry pallet stock is usually prohibitive, and there are risks associated with degrade from drying too fast. Alternatively, chemical dip treatments using an effective fungicide, followed by accelerated air drying (using fans) is the most effective strategy for both preventing mold and maintaining wood quality. Drying treated pallets in a fan shed usually takes 3 to 5 weeks, depending on wood species, part thicknesses, and environmental conditions. Once dry, wood surfaces need protection from re-wetting to prevent mold spores from germinating. Fungicides / Disinfectants dipping or spraying pallets or pallet parts with chemical fungicides provides a thin chemical layer that acts as a barrier against fungal attack. Dip treatment with certain fungicides can be effective for several weeks and longer, depending on the type of chemical and concentration, and moisture content of the wood. The purpose of treating green pallets or pallet parts with fungicides is to protect them from mold long enough for the wood to dry. Disinfectants such as household chlorine bleach can be used to kill mold already on the wood and can remove the surface discoloration caused by mold. However, bleach is only effective for a day or two, and will not prevent mold from re-forming. Good housekeeping: Reducing the spore density in the air and on surfaces around manufacturing and storage areas will help minimize the potential for mold growth. For best results, periodically wash the walls, floors, and ceilings in manufacturing and storage areas using a safe and effective fungicide designed for such use. This will not only not only kill existing mold spores in these areas, but prevent them from germinating for extended periods of time. X-M Industries, Inc. manufactures a product called Mold Extinguisher that is designed for this type of use. Chlorine bleach can also be used to reduce mold spore concentrations in these environments, but it won t offer lasting protection. Also, unused woodpiles, wood scrap, and other waste that could be breeding areas for mold should be eliminated. This will significantly reduce the number of mold spores in the air and on wood surfaces. Each of the above criteria should be incorporated into a continuous mold control program. Each mold control program must be customized to fit different manufacturing, shipping, and storage environments. 2

3 PROJECT OBJECTIVES To evaluate the performance and effectiveness of X-M Industries, Inc. E-Fusion chemical wood coating in preventing mold from growing on green (wet) wood pallet components. MATERIALS & METHODS - E-FUSION-RTU treatment (in liquid form) was provided by X-M Industries, Inc (Norcross, GA). - ASTM D : Standard Method for Testing Fungicides for Controlling Saptain and Mold on Unseasoned Lumber (Laboratory Method) was used to test and evaluate the potential of E-Fusion as an effective fungicide for preventing mold from growing on green wood pallet components. While this methodology prescribes a 4-week test and evaluation period, X-M Industries requested the duration be increased to 12 weeks. Due to this increased time interval, samples treated with E-Fusion were re-inoculated with mold spores after 10 weeks to evaluate the long term efficacy of the treatment. A second treatment of E- Fusion was never applied to the samples. - Small wood test specimens were dip treated in E-Fusion for approximately 30 seconds. Untreated controls samples were also used in this study. All test specimens were green at time of testing (moisture contents > 50%). All test specimens, both treated and untreated, were inoculated with three types of common mold spores: Penicillium spp., Aspergillis spp., and Trichoderma spp. Inoculation consisted of saturating wood specimen surfaces with mold spores suspended in water. The wood test specimens included three wood species commonly used for manufacturing pallets: Southern yellow pine (SYP, Pinus spp.), oak (quercus spp.), and Yellow poplar (Liriodendron tulipifera). - All test samples were maintained inside a temperature/humidity chamber at 30 o C (86 o F) and 100% humidity. Test samples were evaluated for mold growth every 2 weeks over the 12 week project duration. Mold formation on the test samples was evaluated by observing the amount of surface area covered with mold, as well as growth intensity. Each sample was scored using a 0 to 5 visual rating system (5 being maximum surface coverage and intensity). - This project was conducted using facilities and equipment at Virginia Tech located in Blacksburg, VA. Experimental Design (Complete Factorial) 3 mold species 3 wood species 2 treatments (including control) 5 replicates Total 90 test samples 3

4 RESULTS & DISCUSSION Table 1 provides a summary of mean scores for each group of 5 test replicates observed and recorded for the first 10 week phase of this evaluation. Table 2 provides a summary of mean scores for samples evaluated 2 weeks after being re-inoculated with mold spores at the 10 week stage of the study. Figures 1 through 3 show examples of untreated control samples, samples treated with E-Fusion after 10 weeks, and re-inoculated E-Fusion samples after 12 weeks, respectfully. Appendix 1-A and B provide raw mold score observations at each two week interval for all samples tested in this study. Table 1 shows that samples treated with E-Fusion chemical fungicide were 100% resistant to mold growth after the initial inoculation of mold spores. No visible mold was observed during this 10 week duration (Figure 2.). In contrast, the untreated samples had abundant mold growth that began forming in the early stages of the test. For pallet manufacturers and their customers who are concerned about mold growing on pallets, the E-fusion product manufactured by X-M Industries provides excellent protection that should last long enough for pallet surfaces to dry to below 20% moisture content. Table 2 shows that trace amounts of mold growth were observed on the E-Fusion treated samples two weeks after the second inoculation with mold spores. This indicates the efficacy of E-Fusion does decrease over time. As indicated, the intent of using a chemical fungicide on pallets is to provide mold protection while pallets have time to dry. The mold protection provided by E-Fusion exceeds this requirement for most conditions of pallet use. Pallets must be protected from subsequent exposure to water. 4

5 Table 1. Average mold scores for all wood samples and treatment combinations over the 10- week evaluation period. Scores range from 0 to 5 (0 = no mold visible; 5 = mold intensely covering wood surfaces). Table 2. Average mold scores for E-Fusion samples that were re-inoculated with mold spores after 10 weeks and re-evaluated two weeks later (at the 12-week mark). * indicates mold scores on E-Fusion samples re-inoculated after 10 weeks (note: control samples were not re-inoculated after 10 weeks) 5

6 Figure 1. Untreated control test samples 12 weeks after being inoculated with mold spores. Mold is clearly visible and intensely covering the wood surfaces. 6

7 Figure 2. Samples treated with E-Fusion 10 weeks after being inoculated with mold spores. No visible mold can be observed on the wood surfaces. 7

8 Figure 3. Samples treated with E-Fusion that were inoculated with mold spores a second time 10 weeks after the initial inoculation. This image shows trace amounts of mold visible at the 12 week evaluation (two weeks after the second inoculation). 8

9 APPENDIX 1-A Control Samples. Visual mold score observations for all untreated test samples at two week intervals over a 12 week evaluation period. Scores range from 0 to 5 (0 = no mold visible; 5 = mold intensely covering wood surfaces). 9

10 APPENDIX 1-B E-Fusion Samples. Visual mold score observations for all test samples dip treated with E-Fusion chemical at two week intervals over a 12 week evaluation period. Scores range from 0 to 5 (0 = no mold visible; 5 = mold intensely covering wood surfaces). 10

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