Is It High Time for Hemp-Based Composite Panels?

BY DAVID KOENIGThe continuing volatility in wood prices may finally create an opening for a new generation of composite products that use hemp in place of wood fiber. For more than 30 years, manufacturers have been trying to turn hemp and other agrifiber composites into substitutes for wood boards and panels. The most successful results have used wheat straw, but there have also been attempts that employed rice straw, grass straw, cotton stalks, soybean stalks, kenaf, and hemp. The plants are all plentiful, adaptable, and lightning-fast to grow. Hemp, for instance, can grow from seed to harvest in three to four months. In fact, hemp—the non-psychoactive form of the cannabis plant— is a natural as a building material. It has been used for thousands of years for rope and continues to rise in popularity in insulation (either as pressed coreboard or hemp wool) and as a concrete substitute (called hempcrete). Traditionally, the most significant limitations have been legality (a problem solved with an amendment to the U.S. Farm bill in 2018) and cost (hemp insulation and hempcrete can cost more than the products they replace by 50% or more). However, recent wood price spikes have made hemp-based lumber and wood-panel substitutes considerably less expensive. Typically, the substitutes are produced in ways reminiscent of the production of traditional engineered wood products, including MDF, OSB, I-joists, and LVL. The first of them came in the early 1990s, when C&S Specialty Builders Supply, Harrisburg, Oregon, imported regulated bales of hemp to develop its own MDF, with an assist from researchers at Washington State University Wood

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Materials & Engineering Laboratory. They claimed their product proved to be two-and-a-half times stronger than MDF composites. In 2018, CannaGrove, a division of Hemp Traders, Paramount, California, introduced CannaBoard particleboard, which incorporates hemp fibers and a non-toxic, formaldehyde-free resin as a binder. It reportedly can be used in place of all MDF applications, from furniture to subflooring. The company partnered with a manufacturing facility in Idaho to produce limited quantities and was about to go to wide production in 2000. Then the pandemic—and resulting boom in demand for construction products—forced the plant to focus all of its capacity and resources on its core products, leaving CannaGrove without a production partner. CannaGrove is hopeful it will find a new facility and resume production in the second half of 2022.

In 2019, Fibonacci, Murray, Kentucky, launched HempWood pressed-hemp boards and blocks. The aim is to recreate the stability, hardness, density, and workability of oak. HempWood is now offered in 1x10x40 and 1x10x48 panels, 4-ft. boards (5/4x1/4, 2/4, and 4/4), and now 6-ft. boards (5/4x1/4, 2/4, and 4/4).

“The only barrier I see preventing (HempWood) from becoming incredibly popular is the lack of customer knowledge—that it exists—and the price,” noted Danny Clark, whose Reel Lumber Service in Anaheim, California, sells the product throughout the West. “Although HempWood has come down in price, it is still a high-end product. As more people start using it and demand increases, I am convinced the board foot price will continue to drop. The younger kids are demanding alternative products that shout eco-friendly and sustainable, and HempWood is in a good position to fulfill those demands.”

Reel Lumber Service has a local woodworker stabilize the product and dye it various colors for turning on a lathe. The wholesaler also stocks a new, better-performing 6-ft. size. “The 6-ft. blocks are manufactured in a new press that has been mechanized and allows for a much better consistency of density in the boards,” Clark said. “The adhesive strength and water resistance has also been greatly improved, and these boards are also carbon negative.”

While the hemp plant is resistant to mold, it’s highly absorbent of water. Consequently, hemp-based products are most frequently used in interior applications, such as flooring, cabinetry, millwork, and furniture.

Yet manufacturers would like to see not only greater use of hemp-based decorative panels, but expansion to structural applications. PlantD, Durham, North Carolina, has developed a prototype hemp-based OSB. The company hopes to build “microfactories” across the nation, using equipment and technology said to be far less expensive and far more mobile than traditional OSB operations. PlantD is also developing hemp-based laminated veneer lumber for framing and hemp I-joists made from its OSB and LVL components.

Still, no hemp-based materials appear to have taken a noticeable bite out of the market. But if lumber supplies and prices remain unpredictable, it may only be a matter of time before more design and construction professionals turn to agrifibers like hemp. s p

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