Peter Bouckaert, the renowned Belgian beer maker responsible for New Belgium Brewing's groundbreaking sour-beer program and many of its other recipes, is leaving the nation's fourth-largest craft brewery after 21 years to launch a tiny — and mysterious — new project in Fort Collins called Purpose Brewing and Cellars.

Bouckaert is throwing in with Zach and Laura Wilson, who were the head brewer and marketing director, respectively, at 1933 Brewing in Fort Collins before it closed in December 2016. The Wilsons took over the brewery's space, liquor license and equipment a few days later and have been promising big news since then. No one knew how big, though, until Thursday, when Bouckaert announced his plans.

"Right now, I am very excited," he tells Westword. "I feel like a man twenty years younger."

Bouckaert, who studied biochemistry in his native Belgium, started brewing in 1987 for Rodenbach, the famed 200-year-old Belgian sour-beer maker, before starting and running his own brewery for two years. In 1996, he moved to Fort Collins to take over for New Belgium co-founder Jeff Lebesch, who wanted to move on at the young company just one year after starting it in his basement with then-wife Kim Jordan.

At the time, New Belgium was only making five beers (Fat Tire, Sunshine Wheat, Old Cherry, Abbey and Trippel), so Bouckaert began adding seasonals, and in 1997 decided to brew a sour — a bold choice for an American brewery in that decade, when there were almost none. Over the next few years, New Belgium began collecting wooden barrels, known as foeders, for aging the sours, and creating its own strains of lactobacillus and pediocaucus, which are souring bacteria. The project went well: New Belgium won a Great American Beer Festival medal in 2000 in the Belgian-Style Specialty Ales category for La Folie (there was no sour beer category then).

La Folie, a classic Flanders-style sour brown aged in wooden barrels for one to three years, went on to become a standard for New Belgium and one of the most highly rated sours in the United States. Twenty years later, New Belgium has more than 65 foeders in its "foeder forest" and makes around one million barrels of beers per year at its plants in Fort Collins and Asheville, North Carolina. The company is the eighth-largest brewery in the nation, and there are now around fifteen sour- and wild-ale categories at GABF.

"For me, my drive has always been about how to keep on learning. I have learned amazing things at New Belgium that I never thought I would be interested in," Bouckaert says.

Last year, as part of that drive to learn, Bouckaert took a sabbatical from New Belgium — something the company allows its employees to do once every ten years — and traveled the western United States visiting breweries. "I was amazed at how many new things there were and how much beauty there still was in brewing," he explains. "Then I started dreaming about how I could be influential in that, and I started talking to people about what was interesting and exciting and what would make my heart beat the most. But going small was the key to what I wanted to do."

And small is what he will have with the Wilsons and Purpose Brewing. The three "partners" — neither Bouckaert nor the Wilsons will reveal their ownership arrangement — will start off with the four-barrel brewing system acquired from 1933 Brewing. They are also gathering oak wine and whiskey barrels — possibly up to 150 of them — and hope to open their doors sometime this summer.

But their lease only runs for one more year; after that, their goal is to move to a piece of property somewhere nearby where they can operate a farm brewery and grow the majority of their ingredients, from hops and barley to herbs and spices. They also plan to roast their own coffee, which could be incorporated into the beer.

What kind of beers? Again, Bouckaert and the Wilsons are mum. "We don't want to box ourselves into a particular niche," says Laura Wilson. "We want to leave some of it vague and mysterious."

"We are being pretty unspecific on purpose," Bouckaert says. "You will see later as to why we are not disclosing what we are doing yet. We think there will be some exciting surprises."

The Wilsons met Bouckaert through the Fort Collins brewery scene, which Laura describes as being "particularly tight," and got to know him better around the bonfire at an annual camping trip that Fort Collins brewers take to Jester King Brewing in Texas. "That's where the relationship began to flourish," she adds. After his sabbatical, they got to talking again, and "Peter got a little excited about what we wanted to do, and said it might be something he would want to get involved in with us. We spent a lot of time after that writing a business plan together."

Bouckaert says he thought a lot about what kind of project he wanted to take on — and who he wanted to do it with, since he would have had opportunities just about anywhere in the world. But when he got to talking with the Wilsons, he decided that their vision for Purpose Brewing and Cellars was exactly the same as his — though the details are still a mystery.

Whatever they are, they will likely be experimental, says Strange Craft Beer Company owner Tim Myers, who has collaborated with Bouckaert several times, most recently on a beer that the Colorado Brewers Guild made for Collaboration Fest. "I have always enjoyed Peter’s humor and humility, his knowledge, and his generosity when chatting with other brewers. But more so, Peter’s irreverent attitude toward conventional ingredients when creating recipes is always refreshing," Myers says. "I think we spent over an hour at Savory Spice Shop when working on the Centennial Pale pilot batches. Peter is also a huge supporter of Colorado hops and barley growers, and I hope this transition will allow him to flex those creative muscles and bring us many new small-batch brews to enjoy."

In the meantime, though, Bouckaert will remain on board at New Belgium throughout the remainder of 2017, finishing up some projects and helping Kim Jordan, who is still the president and CEO, find his replacement — something that won't be easy. "I only told her about a month ago," Bouckaert says about his announcement. "We had been working together for so long — we have gone through so much beauty and some hard times over the years — that is was a really emotional moment for both of us."

"She said, 'Why are you doing this to me?'" he recalls with a laugh. "But then she said, 'Okay, I admire you.' It was good to see Kim be Kim again. There is so much love there."

New Belgium didn't comment on Bouckaert's departure, but Jordan did issue a statement. “Creative people like new challenges,” she wrote. “He’s got a gig on the side and will be transitioning over the balance of the year. We wish him well; I have loved our time together. Peter and I have had lots of fun and done some beautiful work. Both sides start this transition with the utmost respect and appreciation for all that we’ve accomplished together.”

And when he's not at New Belgium, Bouckaert says he will most likely be cleaning kegs at Purpose. "I hope to be brewing, hosting, writing recipes and cleaning kegs. I think I'll mostly be cleaning kegs."