The job was unglamorous, but important: During an internship ahead of his final year in the fermentation sciences program at the University of California, Davis, Russell Heissner was at Domaine Chandon, tasked with overseeing the last squeeze of the sparkling wine crush. That meant extracting every last bit of liquid from the fibrous stems, seeds, and skins left after pressing the grapes. Even that low-grade, tannic juice could command some market value for the winery, his bosses said. The leftover pomace—or solid remains of the fruit—they believed, could not.

Or could it?

The undergrad Heissner wondered. Knowing organic waste is primarily composed of cellulosic material (or simply, structural types of sugar), he saw untapped potential to reuse the pomace in the further production of alcohol. Nearly 40 years later, after a deliberately circuitous career, Heissner, now 60, is ready to show the beverage industry that its biggest pollution problem could become a boon. In October, Heissner and a business partner, Brian Hollinger, launched Zenso Labs, an innovative biotechnology company and consumer brand, that proves it’s possible to repurpose organic waste as more sellable liquid. The unique Zenso process converts spent grain fiber into drinkable alcohol by adding a proprietary combination of enzymes that are able to break down previously impenetrable structural carbohydrates.

The industry’s current leading solutions for spent grain—shipping it off as animal feed, composting it or recycling it as energy, and reusing it as a culinary ingredient—make use of the protein, vitamins, and minerals in the material. Organic waste also contains carbohydrates, like sugars, starches and lignin, explains Thomas Shellhammer, the Nor’Wester Professor of Fermentation Science at Oregon State University (OSU). Shellhammer was a classmate of Heissner’s at UC Davis and has helped Zenso Labs do some proof-of-concept testing at OSU’s state-of-the-art research brewery. 

Russell Heissner
Photo: Courtesy of Barrel House Z

Humans can’t digest the fibrous husks of grains like barley the same way many animals can, because the sugars are indigestible to our metabolic system, Shellhammer explains. It’s similar in fermentation. “But if we treat these spent materials with enzymes that can actually break down these indigestibles, we can create a new stream of smaller carbohydrate molecules,” aka sugars, Shellhammer explains, which can be used for a variety of biological applications.

For the last year or so, Heissner has been experimenting with turning those sugars into hard seltzer. Zenso Labs currently has two different drinks available at Heissner’s taproom and brewery, Barrel House Z in Weymouth, Mass. Recently, the production team there began packaging Zenso-branded beverages in 12-ounce, slim-can six-packs, with the trademarked slogan “sustainable sipping” ringing the top of each sticker label.

Seltzers hovering around 4.5% and higher proof ready-to-drink cocktails are currently the best vehicles for this fledgling biotechnology, Heissner says, because the liquid sugar the process produces comes “with some unusual flavors. It’s a little sour,” he says. “I have some fine-tuning to do before we get to broader applicability for breweries.” But eventually, perhaps as soon as mid-2024, the technology will be available to license by other producers. 

The problem in perspective

Spent grain comprises upwards of 80% of the solid waste generated by breweries and distilleries, research and reports show. “On the commercial scale, every batch is going to produce anywhere from a few 55-gallon tubs up to filling up an entire silo in just one day,” says Bob Galligan, a former head brewer, director of innovation and sensory specialist, who now serves as the director of industry relations for the Minnesota Crafts Brewers Guild, which maintains a spent grain directory to connect farmers who need animal feed or compost to breweries looking to dispose of spent grain. 

An agricultural waste-management arrangement works well enough for operations that are close to farmland, notes Shellhammer, and can create “a nice little circular economy.” For instance, in November, Portland, Maine, restaurant Central Provisions hosted a full circle dinner and tap takeover with Olde Haven Farm and Cushnoc Brewing Co. Spent grain from the brewery in Augusta traveled just about eight miles to the farm in Chelsea, where it helped feed a pig that the chefs at Central Provisions then transformed into five different pork dishes to pair with a lineup of Cushnoc beers. 

But, there are also drawbacks. Raising livestock and making compost both emit methane, a leading contributor to our warming planet. And for more remote breweries, an agricultural partnership just isn’t possible. Shellhammer points to Alaskan Brewing Co., which developed a first-of-its-kind steam boiler entirely fueled by spent grain to generate its own energy. Previously, like a lot of breweries, Alaskan dried then shipped off its spent grain to be reused in the Lower 48. “People do spend a fair amount of carbon to ship spent grain around,” Shellhammer says. 

Increasingly, there are avenues for breweries to sell, donate, or reuse their spent grain with greater economic value. Anheuser-Busch has developed EverGrain, a technology company that’s repurposing the protein from spent grain into new ingredients, and is making it available to other producers (similar to what Zenso Labs intends to do with the fiber). Spent grain protein has various culinary uses, such as enhancing breads and pizza dough, creating nutrient-rich drinks and snacks, and producing dog treats. 

Collectively, culinary uses for spent grain “might be able to make a dent,” according to Heissner, “but it doesn’t really solve the problem,” since there is still cellulosic material leftover once the protein is extracted. By combining the Zenso process with a commercial use for the protein, Heissner estimates that his 1,000-barrel brewery could minimize the amount of spent grain it has to deal with by 80%. That savings is exciting, but the ultimate driver of Zenso’s potential, he says, is that it uses less grain to make more alcohol—and thus, to make a producer more money.

An aptitude for ethanol

After extracting every last drop of liquid from the pomace at Domaine Chandon, 22-year-old Heissner would drive the debris out to the fields to deposit it. Thinking “there’s got to be a better use for this than turning it into dirt,” he says, “that ended up being a guiding principle for my career.”

Back at UC Davis that fall, Heissner began a course of directed research around converting sugar into fuel ethanol. Upon graduation in 1986, he was tapped by the fledgling Harpoon Brewery to be head brewer and Employee No. 1 in Boston, so he put his hypothesis on hold. Unable to shake the idea of upcycling organic waste, Heissner left Harpoon a few years later and for the next three decades worked to develop biofuel technology.

After his employer was acquired and subsequently shut down by petroleum giant BP, Heissner returned to brewing in 2016 by opening Barrel House Z, located about 15 miles south of Boston. A taproom with a modest production brewery, behind the scenes it’s been a continuous testing ground for Heissner’s experiments in ethanol—this time, for drinking it, not driving with it.

Shortly after opening the brewery, Heissner negotiated licensing the technology he helped develop to use it to make beverage ethanol. “I went back to BP and said, ‘I’ve got some cellulosic material that’s a big problem for breweries and distilleries, and that’s spent grain.’”

During the economically difficult years of the COVID-19 pandemic, Heissner returned to bioengineering as a consultant with Boston-based company, Gingko Bioworks, while his wife, Mary, held things down at Barrel House Z. He maintains his role as director of business development with Gingko. In May 2023, a commercial partner of Ginkgo Bioworks called Ferment Co. invested to help launch the Zenso company.

The technology still needs refinement, says Shellhammer. But initial findings prove “there are ways to get more value out of the material that’s stuck inside spent grain,” he says.

So Heissner remains in the lab at his own, local brewery. Putting Zenso on draft and in cans at Barrel House Z “is all in service of showing it’s possible,” he says. “It just so happens, we’re selling a lot of it.”

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