Advancing Sustainability in Packaging: Optimizing Unit Loads for Environmental Benefits

As global supply networks expand, the sustainability of packaging used in transportation has become a significant concern. The most common type of unit load in the U.S. is based on a wooden pallet that supports various configurations of stacked corrugated boxes; 80% of goods are distributed in this format. End-of-life (EOL) scenarios for packaging have become an area of growing interest. With the rise of concern about sustainability issues, EOL of packaging has drawn tremendous attention due to the high volumes of waste generated across supply chains.

Recent research into unit load cost optimization reveals that enhancing the stiffness of a pallet’s top deck can significantly improve the strength of stacked boxes. This method allows for a reduction in the grade of corrugated board required, leading to more cost-effective unit loads. Despite the financial benefits, there remains a knowledge gap regarding the environmental implications of this optimization approach.

To address this gap, Dr. Laszlo Horvath assigned Saewhan Kim, Ph.D. Candidate, to conduct research into unit load optimization. A life cycle analysis (LCA) was conducted to investigate the environmental implications of optimizing unit loads through increased pallet top deck stiffness. The environmental impacts of unit load design scenarios were investigated using varied wood species, pallet top deck thicknesses, corrugated boxes sizes, corrugated flutes, and board grades. Testing both initial and optimized unit load scenarios ensured that the new designs offered equivalent performance.

This study compared a wide range of paired initial and optimized unit load scenarios to investigate at what point they cross the line to show measurable environmental benefits through this unit load optimization method. Each scenario involved a 48 in. x 40 in. GMA-style stringer class wooden pallet and one of three sizes of corrugated boxes. The optimization method primarily involved adding chemically unprocessed wood materials to the pallets’ top decks to reduce the chemically processed materials in the corrugated boxes.

A total of ten impact categories were analyzed, calculated, and presented including ozone depletion; global warming; smog; acidification; eutrophication; carcinogens (measured in comparative toxic units for humans); non-carcinogens; respiratory effects; ecotoxicity (measured in comparative toxic units for aquatic ecosystems); and fossil fuel depletion. The results indicated significant environmental benefits based on the unit load optimization ratio (UOR) calculated for each wood species group.

Overall, the findings revealed that the unit load optimization method could enhance environmental performance when the UOR reached a specific threshold. The LCA results indicate that optimizing the unit load by this method could reduce environmental impacts by up to 23%, with benefits accruing across most impact categories primarily due to the reduction in corrugated materials used. The findings revealed that the unit load optimization method could enhance environmental performance when the UOR reached a specific threshold. LCA results showed that optimized unit loads could reduce environmental impacts by up to 23%, with improvements across most impact categories due to the reduction in corrugated materials used. The exception was ozone depletion, which was primarily affected by the increase in pallet materials.

This general trend of environmental benefits being observed in more impact categories as the UOR increases remained unchanged across all investigated wood species groups. A higher UOR signifies that the optimization process requires proportionally less increase in pallet wood compared to the decrease in corrugated materials. In other words, a higher UOR utilizes a better ratio of chemically unprocessed materials compared to chemically processed materials. In fact, the optimization process improved environmental performance by 22.93%, 22.85%, 20.48%, and 13.16% for the high-density hardwood group (HD HW), low-density hardwood group (LD HW), green southern yellow pine group (GSYP), and kiln-dried southern yellow pine group (KD SYP), respectively.

This pioneering study suggests that the packaging industry can achieve environmental improvements in distribution packaging by applying engineering principles to the physical interactions within packaging systems, rather than developing entirely new packaging systems. The research provides preliminary guidelines for determining the effectiveness of unit load optimization, with sensitivity analyses confirming that these guidelines remain valid across different transportation distances.

The study demonstrates that increasing the stiffness of pallet top decks and reducing the grade of corrugated board can effectively reduce the overall environmental impact and cost of transported unit loads. This approach not only addresses sustainability concerns but also offers practical, economically viable solutions for the packaging and supply chain industry.