By Dan Lemke
Minnesota’s emerging hemp industry may be in a prime position to help one of the state’s largest agencies solve a problem while also opening doors to potential new markets.
The Minnesota Department of Transportation (MnDOT) conducts dozens of road construction or repair projects each year. To minimize environmental impact, nearly every one of those projects requires some level of erosion control.
“Erosion control is an important piece for most of our construction projects,” says Ken Graeve, MnDOT erosion and stormwater supervisor. “Any project that disturbs soil has to have some erosion control and sediment control work done.”
Some of the products MnDOT has used, including erosion control mats, contain plastic netting, which is used to hold layers of materials like straw or wood fibers together. The mats hold soil in place while allowing water to pass through and plants to grow gradually through the material. Graeve says the plastic netting is problematic. Small animals like ducklings and snakes get tangled in the netting. Additionally, the netting tends to get wrapped up in mowing equipment, creating headaches for mowing crews and mechanics. The plastic also does not biodegrade so it eventually creates microplastics, contributing to other environmental problems. Some of the plastic netting has been replaced with jute, but that product must be shipped in from overseas. Graeve says MnDOT is looking for a local, more sustainable substitute.
Enter Hemp
For the past three years, AURI has led a project supported by MnDOT and the Minnesota Department of Agriculture to explore the potential of using industrial hemp fiber in erosion and sediment control products. Funding for the project was provided by the Minnesota Environment and Natural Resources Trust Fund by the Legislative-Citizen Commission on Minnesota Resources (LCCMR). The Trust Fund is a permanent fund constitutionally established by the citizens of Minnesota to assist in the protection, conservation, preservation, and enhancement of the state’s air, water, land, fish, wildlife, and other natural resources.
AURI has had a hemp initiative for several years, which is focused on developing a value chain for industrial hemp. For the erosion control project, AURI worked to develop methods for processing hemp stalks, separating the fibrous inner stalk from the woody outer core called the hurd.
At AURI’s Bioindustrial Innovation Center in Waseca, Minnesota, hemp fibers were produced for testing in mats, hydromulch sprayed on the soil, erosion control logs, and silt fences. Fibers were even spun into yarn in an attempt to weave hemp fibers into the netting that holds mats together.
“We’ve done initial work on all of those products, but the ones that we think have the most opportunity based on research, field testing, and lab testing, are the blankets and the hydromulch,” says Matthew Leiphon, AURI project manager. “We still think there’s potential for the logs and potentially the silt fences, but the mats and hydromulch make the most sense right now.”
AURI staff connected with several private industry partners to develop erosion control prototypes. The prototypes came in various thicknesses and blends of other ag-based materials with hemp fibers. Products were tested at several locations, including at MnDOT’s MnROAD test site near Albertville, Minnesota.
“Our goal for this project was to find a biobased solution for MnDOT.
They need an alternative to any synthetics being used in mats, but that still meets the necessary specifications and performs correctly,”
says AURI Business and Industry Development Director Harold Stanislawski. “The second part of that goal is to use industrial hemp, get acres of it planted, and develop value-added uses and end markets.”
Minnesota farmers planted about 1,100 acres of industrial hemp in 2023. Additional hemp processing capacity is coming online in Minnesota, so finding potential markets for hemp fibers would boost the industry.
Market Potential
Graeve says any alternative erosion control product must perform as well as what MnDOT currently uses. Most temporary erosion control items need to last between three and 18 months before decomposing. Price and convenience are also considerations.
The results of the hemp product tests are encouraging.
“There’s really good potential for hemp products,” Graeve explains. “With the demonstration that we did and the lab testing, it looks like the products perform similarly to the ones we currently use.”
Graeve says MnDOT-led construction projects use about 4 million pounds of products and $6 million to $10 million worth of erosion and sediment control materials that could incorporate or be replaced by hemp. Those are just MnDOT projects.
“Many Minnesota cities, counties, and private projects also use our specifications and, therefore, our materials,” Graeve says. “We have no way of knowing exactly how much is used, but our general rule of thumb based on conversations with vendors is that the overall use of these products is about five to ten times as much as what MnDOT itself uses.”
Because erosion control products do not require a high level of processing, Graeve sees them as a good entry point for Minnesota-grown hemp products.
“From the standpoint of the Upper Midwest and anywhere that erosion control products are needed, there’s a big market,” Stanislawski says.
Next Phase
This project illustrated that erosion control items and mulch offer one viable market for hemp. Stanislawski adds that most hemp processing will use the seeds for food and industrial products, both key market opportunities. Utilizing fiber would offer growers and processors additional revenue sources.
“We’re going to harvest the seed, and we’re going to use that seed, likely for an industrial or a food process, so there’s revenue to be obtained there,” Stanislawksi states. “You’ve still got the stalks and the hurd from the dual-purpose variety that you could monetize. In the case of erosion control, you’d be monetizing the fiber, and then you can monetize the hurd for other markets, such as hempcrete or bedding.”
AURI and MnDOT hosted a field day at the MnROAD facility in the fall of 2023. The event gave growers, vendors, and manufacturers an opportunity to learn about the research and to make connections for potential future developments.
AURI Senior Scientist for Coproducts Alan Doering says AURI’s next step is to share the information gathered through the project research with industry partners, growers, and processors.
A priority for this project was to develop new markets for hemp fiber that benefit producers and processors in the state,” Doering says. “I foresee additional research in the area of erosion control mat refinement, focusing on cost and performance improvements, specifically related to promoting vegetation to grow through the mats.
Doering expects another next step will involve producing a hemp-based thread on a larger scale, focusing on the cost and feasibility of hemp yarns compared to natural fiber-based yarns currently in the marketplace. He also anticipates expanding research on utilizing various hemp coproducts within erosion control products, such as hemp-filled erosion control logs, which is a fiber-filled mesh tube used to control water descending from slopes.
