Wood is better. No, plastic is the best. No, wood is the eco bomb. Well, plastic lasts longer. Yeah, like thousands of years in a landfill. Well, wood is expendable and wastes resources. Wood is recyclable. So, is plastic. Plastic is lighter and saves on fuel impacts. Well, wood pallets are made from a renewal resource and has less of a carbon footprint. The debate rages on. And that’s why researchers from Penn State University sought to answer the question, “Which pallet is truly greener – wood or plastic?”
“What was lacking in this whole arena was a comprehensive life-cycle analysis, and that is what this study provides,” said Chuck Ray, associate professor of ecosystem science and management in the College of Agricultural Sciences. “More than a decade ago, other studies were commissioned by the wood pallet industry and by the plastic pallet industry, and of course those results favored the funders. This is the first academic, peer-reviewed study to compare the life-cycle environmental impacts of different pallets in use, and it was performed without external funding that could potentially bias the findings.”
With over two billion pallets in use in the United States, the material used in the pallet makes a difference. Penn State researchers conducted a series of ultra-detailed comparisons looking at the performance of treated wooden and plastic pallets through a detailed, cradle-to-grave life-cycle assessment, and conducted an analysis of treatments required to kill pests such as insects. They investigated and evaluated the environmental impacts of resources consumed and emissions released by wooden and plastic pallets throughout their life cycles.
Plastic pallets have a much longer life cycle than wooden pallets because plastic pallets are usually not broken or damaged and normally can travel more than 200 round trips before being taken out of service. But they are typically derived from petroleum or natural gas products, which greatly increases their carbon footprint. The Penn State analysis took the assumption of 100 trips for a plastic pallet and 33 trips for a quality, pooled, wooden pallet. These are the trip assumptions used in the previous industry studies.
The Penn State study compared the environmental impacts of the pallets on a one-trip basis and 100,000-trips basis under nine impact categories chosen by researchers because of their environmental relevance. The categories included: influence on ozone layer depletion, respiratory organics, aquatic ecotoxicity, terrestrial ecotoxicity, land occupation, aquatic acidification, aquatic eutrophication, global warming and non-renewable energy.
So, what are the results? Chuck Ray and his research team concluded that shipping pallets made of wood are slightly more environmentally friendly and sustainable than those made of plastic. Their findings were recently published in the Journal of Industrial Ecology. Penn State researchers showed that on a one-trip basis, wooden pallets treated with conventional kiln heating and as-yet novel, radio-frequency heat treatment incur an overall carbon footprint that is slightly lower than plastic pallets during their life cycle. For the 100,000-trips comparison, the results remained consistently in wood’s favor, with only one category changing from pro-wood to pro-plastic.
“It should be noted that wooden pallets that are heat-treated to kill pests incur a carbon footprint 20% to 30% lower than those treated with methyl bromide fumigation,” Ray said. “Methyl bromide gas has been blamed for depleting the Earth’s ozone layer. And theoretical calculations of the resource consumption and emissions of radio-frequency treatment of pallets suggest that the new dielectric technology may provide a lower-carbon alternative to both conventionally treated wooden pallets or plastic pallets.”
Wood did better than plastic in seven out of the nine categories for one-trip analysis. The only categories where plastic came out ahead were respiratory organics and land occupation. Respiratory organics deals with volatile organic compounds (VOCs) released in the manufacturing or lumber and drying of pallets. Land occupation points to the larger amount of land required to grow trees for forest products compared to the much smaller amount of land needed for petroleum or natural gas production, the raw materials for most plastics. However, this isn’t really a negative depending on how you look at it. Wood grown in sustainable forests is a carbon sink and positive for many ecological processes. Think of it this way. Would we rather have more forests or condos or retail stores or petroleum exploration platforms? The ecologist is going to say forests every time.
When the researchers looked at 100,000 trips (which may be a good baseline for medium to large pallet users in a year), the only other category where wood did worse than plastics was non-renewable energy due to the higher number of pallets produced and related transportation effects. Categories where wood does better include: ozone layer depletion, ecotoxicity, acidification and most importantly, global warming.
Ray and his team conducted the research because there was a lot of confusion out there as well as some gaps in the research. For example, previous analysis of wood pallets had not considered the impacts of ISPM-15 treatment. The other studies came up with significantly different conclusions. Ray explained, “It did not occur to me to do this research until the plastic pallet industry started talking about their products as environmentally superior. I questioned that statement and decided to do life-cycle analyses.”
As the only peer-reviewed, LCA study on pooled wood vs. plastic usage, this analysis seeks to provide unbiased analysis. Ray admitted, “When our team started out, we had people who thought various conclusions were likely, and we decided to run the analysis as an independent research voice to found out.”
So, what does this mean for pallet providers or users? Let’s be clear. Any application must be based on the trip and usage model that is commonplace for a particular supply chain. Number of trips achieved, distances traveled to reposition and retrieve pallets, and real-world recycling of the product all impact the real-world results of an LCA. For example, companies may claim to recycle a pallet, but they may not do it in every case due to the difficulty in locating and repositioning strays, challenges in recycling markets, complexity of the pallet design, and so on. This analysis by Penn State assumes the pallets are recycled and reused.
Overall, the conclusions are good for wood. Pallet companies can use this information when talking about the green credentials of various pallet designs and materials. But the industry does need to be careful spiking the ball too much, because every product has some environmental cost. The good news is that wood pallets have a competitive and compelling ecological story. And this research just goes one step further in supporting the claim that wood is indeed very green.
