The Asheville Nuttery is a cooperative-owned nut processing facility in Asheville NC that houses equipment and staff to process Black walnuts, hickory nuts, hazelnuts, and even acorns into shelled nuts, flour and oils. Visitors are encouraged to bring in their own gathered nuts, in exchange for processed nuts or cash. Their work is part of a larger movement to bolster community-powered fruit and nut production throughout the Southern Appalachians. Working with our friends at Cooperate WNC, in the fall of 2022, the Asheville Nuttery was awarded a grant to improve their processing equipment by funding the fabrication of a new higher-capacity huller.
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Walnut hulls rot quickly after falling from the tree.
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Resembling tennis balls, freshly fallen black walnuts are easily recognized by the green fleshy hull that covers the hard-shelled nut underneath. After falling, the hulls will quickly rot into a dark black, gooey mass that easily stains hands and clothes. Hulling can be real time-consuming, and it’s one of the only operations that is time-sensitive; it’s essential to remove the hull quickly to prevent spoilage. Once nuts are hulled and cleaned, they can be dried and kept in long-term storage, but for a few short weeks in late fall, hulling is absolutely the bottleneck of the processing line.
Designed with a 16 hp engine that turns a welded chain beater bar at 500 RPM, this new huller can process a 5 gallon bucket of nuts in less than a minute. When set up with infeed and outfeed conveyors the huller can operate as part of continuous process - whole nuts are rated in via lift conveyor into the top, shredded hulls drop out the bottom grate and whole nuts are pushed out the outfeed hopper on the far end. The Nuttery has achieved up to 550 lbs per hour throughput - a massive jump in labor efficiency that tips the scales toward a profitable business model.
This first generation machine is not without its faults: it’s loud, and there remains some losses as smaller nuts fall through the lower grate, or weaker nuts are cracked before exiting. A second version of this machine may include tapered beater chains and a wider adjustment in RPM to more precisely match the speed of the infeed conveyor. Still, overall, these losses are acceptable when balanced against the overall efficiency of processing time.
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| Version 1 of the new huller for the Asheville Nuttery. Fabrication costs were
kept lower by incorporating scrapyard-sourced steel when possible. |
This is peak black walnut season, and given the excitement around watching the Nuttery’s processing line in action I thought now would be a good time to give a brief tribute to the many offerings of the Black Walnut tree. Many are familiar with the deep purple tones of black walnut lumber, or the earthy, bitter flavors of the nutmeat, but that’s not all the black walnut tree has to offer. Here are three other unique and practical products sourced from the black walnut tree:
Dye, Wood Stain and Ink
When left to rot, the hard green hulls will turn to a very mushy dark brown ooze that can be further refined to make a resilient, comparably lightfast ink, dye or stain. Best and easiest practice is to collect hulls in a bucket, cover with water, put a lid on it, and let it ferment for a few weeks. Alternatively you can gently simmer this walnut hull soup for a few hours, but be sure to do this outdoors, it's not a smell you want in your house. I prefer to let nature do the work of extracting jugalone from the hulls. Either way, strain the solids with a series of increasingly fine filters; You’ll want all the solids out before proceeding.
You can use it now as weak dye on both cellulose and animal fiber. At this point the color will likely be closer to distinct brownish-yellow. A rich, dark brown can be achieved by further concentrating the dye by slow boiling until the volume is reduced by at least half. Further reducing the volume will yield an even thicker, darker dye that can be painted, or used as a wood stain. Adding small amounts of iron (e.g. nails, iron filings) now will shift the color towards black. Preserve your dye/stain with a small amount of isopropyl alcohol and store in jars away from sunlight. Further processing with gum arabic will thicken the dye to yield a smooth-flowing fairly resilient natural ink.
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Black walnut dyed cotton napkins
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Two white oak boards: one unfinished and one stained with walnut hulls
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My daughter's artwork: black walnut and pokeberry inks.
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Drying oil for Fine Arts
Walnuts contain a large percentage of the same fats found in linseed oil. Like linseed oil, walnut oil is a drying oil that, over time, will harden to a tough flexible film when applied in a thin layer and exposed to oxygen. Cross-linking, or polymerization, via oxidation of polyunsaturated fats is the mode of action here, not “drying” as evaporated water. Walnut oil has applications in woodworking as a food-safe alternative to the much more common, chemically-processed linseed-oils, but I’ll be using my walnut oil along with my homegrown pigments to make fine art paints. Refined walnut oil was often used by the renaissance masters as a base for oil paints. It doesn’t turn whites yellow like traditional linseed oil does, and for this reason, some artists still prefer it over the alternatives.
There are various methods for refining walnut (or linseed) oil for painting. One such method, described
here, involves repeatedly washing the oil with a solution of salt water and silica sand to remove mucilage, followed by the lengthy process of clarification by sunlight exposure. In my research, all accounts of walnut oil as a paint medium are from pressed English walnuts (Juglans regia); in my work I’ll be exploring the viability of using similar methods to refine the oil from pressed Black walnuts (Juglans nigra). I started with a half-gallon of aged cold-pressed oil from the Asheville Nuttery. This oil had sat for too long in a bucket with nut meat solids and was deemed no longer viable as a culinary oil. From this oil, my goal is to make a useful base that is suitable for blending with my own homegrown pigments into fine oil paints.
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| Removing mucilage with salt water, pool filter sand, and a pinch of
glass dust. Starting with ½ gallon of raw oil, my final yield after
washing is closer to 1 quart. |
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| Clarifying in the sun. This will take several months. |
Walnut shell biochar
Following removal of nut meat, commercial processors of walnuts will often process leftover shells by grinding them and sifting them through a series of screens. Consistent, smaller pieces are sold as a softer alternative to sand as blasting media, especially in applications involving softer metals like aluminum. Crushed shells are angular and tough, and are still hard enough to remove paint and finishes, but often not hard enough to damage the underlying form. It’s these same qualities that make walnut shell biochar useful as a hydroponic media.
Biochar is made through controlled heating of organic residues in the absence of oxygen called pyrolysis. Depending on feedstocks and other conditions, there are many ways to do this; when using small, consistent sized chunks like walnut shells or screened and dried wood chips there are very simple DIY production methods that yield a very high quality biochar. Following pyrolysis, walnut shell biochar maintains its hard, glassy and angular shape and takes on the filtration and microbially-beneficial qualities of biochar. When used as a fertilizer, walnut shell biochar brings in a lot of potassium and micronutrients and due to its potentially high anion exchange capacity, walnut shell biochar performs especially well when balanced with the nitrogen and phosphorus in urine. Above all, as a hydroponic media, walnut shell differs from other biochars, where it maintains its structure after repeated use. For these reasons, walnut shell biochar is a lightweight and locally-produced and cost-effective alternative to conventional gravel or aerated clay media.
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| Swiss chard absolutely loves my black-walnut shell biochar media. |
