Black Walnuts in Iowa

March 2007

Black walnuts grown in Iowa have two primary end uses, nuts and wood. Both are in demand.

“Black walnuts produce small kernels relative to the nuts’ size, have hard, thick shells, and are difficult to hull. These traits reduce their commercial appeal,” Walnuts: Second Biggest Nut Crop Produced in the United States, Economic Research Service, USDA.

Based on existing research taking place on black walnuts, improved tree cultivars for nut production appears to be the primary focus. Little to no research exists for other uses.

An industry update published in 1998 said more research was needed before marketing walnut hulls and black walnut oil.

“Hull, or the green/black outside husk of the black walnut, is not presently marketed extensively. The hull is typically removed at the nut buying stations and is spread on pastures or other land areas where it oxidizes quickly. It can be used as a natural stain, but the water-weight and handling make transportation unfeasible. There are some interesting potential uses for black walnut hulls that could create markets for some of the hull, including medicinal applications or nutrition supplements. More research is needed, however, before the benefits can be proven and any markets developed.

“Black walnut oil has potential but is not being produced or marketed at this time. Research has been done on extracting edible oil, and preliminary surveys show some interest in the flavorful nut oil for use on salads and other foods, such as olive or other nut oils. The nutrition profile is positive and the flavor seems to have some appeal. More extensive market research will determine whether black walnut oil has real potential as a profitable by-product of the black walnut nut industry.”

Ten years ago, a forestry industry expert indicated helping a black walnut client with locating a niche market for the walnut shells. Catherine M. Mater, Vice President of Mater Engineering Ltd. in Corvallis, Oregon, said the following during a presentation on consumer trends and market opportunities.

“For black walnut (Juglans nigra), we were working with the largest black walnut producer in North America. . . . There were so many hulls the biomass was filling lands outside their own timber operations. So they asked us whether there was a market for the hulls. We had to go to Europe to track this down, but we found that the international cosmetic industry was looking for dried, milled black walnut hulls. Why? Not for facial scrubs, but for self-tanning cosmetics. It is big business-200,000 pounds annually.”

The largest regional, if not the national leader in black walnuts, is Hammon’s Products of Stockton, Missouri. According to the company website, Hammon purchased more than 28 million pounds of nuts in 2006 from approximately 260 buying locations in a 16-state area. The 2005 harvest was 36 million pounds. Black walnuts are one of the few nut crops still picked by hand. Boone, Iowa, was one of seven hulling locations the company traveled to in Iowa.

Hammons advertises six different grades of ground walnut shells for industrial uses. American Forests described the following uses for ground shells.

“The industry functions as much because there is a market for ground-up black walnut shells. That ground meal goes into products that are used for metal cleaning and polishing, in oil well drilling, and as an ingredient in paint and explosives. In addition to cabinets and furniture, black walnut has been used for musical instruments, paneling, gunstocks, and other fancy wood products. The wood is dark purplish-brown, with a fine grain and luster.”

With regard to the many links on the Internet advertising black walnut products in herbal or dietary supplements, those products are not regulated the same as prescription or over-the-counter medicine. The National Center for Complementary and Alternative Medicine, a division of the National Institutes of Health, does research on complementary and alternative medicine.

“In the United States, herbal and other dietary supplements are regulated by the U.S. Food and Drug Administration (FDA) as foods. This means that they do not have to meet the same standards as drugs and over-the-counter medications for proof of safety, effectiveness, and what the FDA calls Good Manufacturing Practices.”

Trees Forever conducted a survey of 21 growers and 15 buyers of nontimber specialty forest products in 2004. The study was funded with a grant from the Leopold Center for Sustainable Agriculture at Iowa State University.

“Of the 15 buyers interviewed, nine are already buying edible nontimber forest products locally and are interested in finding more local sources of butternuts, walnuts, hickory nuts and hazelnuts. Buyers are interested most in seasonal products. They value having products delivered to them as an “as-needed” basis and are not interested in needing to store an inventory. Buyers prefer the least amount of processing necessary for them to sell locally produced nontimber products. Chestnuts were often cited as being too difficult to process.”

“Buyers of edible products, particularly nuts and maple syrup, tend to be food cooperatives and health food stores. Consumers frequenting these establishments typically are better educated about the community and health benefits of buying locally and are willing to pay a premium for those products. Nevertheless, processing is again a big concern for these retailers. They typically buy presorted nuts in bulk and either sell them in bulk or do a minimum amount of processing, often nothing more than re-sorting them into smaller containers.”

A possible option would be to sell nuts directly to Iowa end users. The nuts would need to be further processed. Mechanical nut hullers built in Canada cost between $2,000 and $2,500. If you sell a food product, it will also require a product label.