MCDOWELL, Va, (AP) — Christoph Herby stands inside his 96-square-foot sugar shed and watches the sap hauled from his black walnut trees boil. Steam rises from the evaporator and the air smells of buttered popcorn.

“That’s our liquid gold,” he says, noting the intense labor that goes into making walnut syrup.

Tonoloway Farm, a first-generation syrup operation run by Christoph and Lauren Herby in Highland County, is believed to be the only commercial producer of walnut syrup in Virginia.

But that could change. Researchers in Virginia and West Virginia hope to expand the industry, making the states leaders in the lesser-known but highly sought-after walnut syrup.

Highland County is well-known for its maple syrup. Its annual maple festival — initially scheduled for this month, but postponed amid concerns about the novel coronavirus — draws thousands to the sugar camps that dot the bucolic landscape.

Like maple syrup, walnut syrup is made by tapping trees for sap and boiling it. But walnut syrup is more difficult to make. Sap from black walnut trees contains pectin, a gelatinous substance used for setting jams and jellies, which complicates the filtering process.

Additionally, Herby said the sap yield is significantly lower in the black walnut trees on their property, a trickle compared to sugar maple trees.

The couple tapped both types of trees this year — 640 maples and 420 walnuts. Herby said they expect to produce more than 100 gallons of maple syrup compared to 10 gallons of walnut syrup. That’s more than it sounds like, he noted, since few people purchase syrup by the gallon.

It’s a significant increase from the year before, which was the Herbys’ first producing syrup. The couple produced a very small amount of walnut syrup — really just enough for one pancake breakfast, Herby said — to see if it was possible. After determining it was, they decided to scale up for year two.

“This year is kind of our proof-of-concept year,” Herby said.

Tonoloway Farm sells not only maple and walnut syrups, but also a blend of the two, which has a complex, nutty flavor.

“It’s a taste of Appalachian hardwoods — not just maple, not just walnut, but it’s kind of this local blend of what our trees are producing,” he said.

When the Herbys first decided to make syrup and began walking their land in search of sugar maple trees, they found tons of black walnut trees, he said.

Typically, Herby said, walnut trees dot the forest. That so many walnut trees are concentrated in one place makes the couple’s farm unique. There are hundreds of walnut trees on their land that could be tapped.

It turned out Tonoloway Farm is better suited for a walnut syrup operation than maple syrup.

“You live somewhere and it takes time to learn what the land wants to do,” Herby said. “And in our case this land is very well-suited to walnut syrup.”

The Herbys see potential for the walnut syrup industry to grow in Virginia. It’s unlikely that theirs is the only farm on which black walnut trees are plentiful — though they might be the only ones with the “wild ambition” to make syrup from them.

Mike Rechlin, maple commodity specialist for Future Generations University in West Virginia, likes to refer to walnut syrup as an “untapped resource.”

There’s still much to learn about walnut syrup and the most efficient ways to produce it, but he believes it could be a boon for farmers.

“I will say that Virginia and West Virginia could be the Vermont of walnut syrup,” Rechlin said.

People who have made maple syrup all their life will confess that walnut syrup is better, he said. Many producers have told Rechlin so.

But very little is produced currently, making it a high-value product. Rechlin said that online, walnut syrup can go for $400 to $500 a gallon, though few customers, if any, would buy that quantity.

It’s something southern syrup producers could capitalize on.

“We have quite a walnut resource down here, a resource that they don’t have up in New England, which dominates the maple business,” he said.

In addition to traditional uses — though it’s a little pricey to regularly use it on pancakes — Rechlin said walnut syrup is being used in cocktails and specialty high-end food products.

Rechlin is researching ways to increase walnut sap production to make it more economically viable. He’s also looking to make it easier to produce, like finding a work-around for the pectin problem.