From using rainwater to the contents of unfinished bottles, distillers are pulling out all the stops to become more environmental.

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If the thought of leftover, unfinished bottles from last night's party sounds unsettling to you, you're not alone. But Joe Heron, co-owner of Louisville Kentucky's Copper & Kings distillery, wants you to reconsider.

As of this past January, Heron has been dumping all of the unfinished bottles from distillery events into a “Let the Mystery Be” barrel, to be redistilled into a kind of mystery spirit. The first batch is just coming off the still, and according to Heron, it tastes similar to his brandy, which stands to reason, since that’s mostly what is being redistilled (along with some beer, wine, citrus, and soda). He describes it as smooth and sweet with a hint of salt, but thinks it still needs to be refined. He plans to continue aging the spirit for two to four more years, and will eventually sell it in 200 ml bottles for about $25 apiece, with all proceeds going to an environmental charity of his choosing. A limited run of commemorative un-aged bottles will be available at the distillery in a few months as well.

“We don’t do much with the liquid beyond dump and collect,” says Heron. “Then we will put it into the still and await beauty (or the beast).” This will be an ongoing project and each batch will be a little different. Legally, the spirit will be defined as a “distilled spirit specialty,” the Alcohol and Tobacco Tax Trade Bureau’s catchall phrase for something that doesn’t fit into a clearly defined category.

Heron credits the Trash Tiki movement — which encourages bartenders to use food scraps and other potential waste in cocktails — with inspiring him to experiment. “Many people sleepwalk through life with a lethargy born out of the idea that ‘I am too small to make a difference,’” Heron says. “Bartenders are not somnambulists — they are one of the most actively engaged groups of people on the planet. This curiosity, enthusiasm and culture is what is making bartenders as influential a group of people as exist.”

Heron might be pushing the envelope with his Let the Mystery Be experiment, but he's not the only one. All over the world, from London to California, bartenders are experimenting with different ways to be more sustainable. Take Belgrove Distillery in Tasmania, who distilled something it's calling “Kissing a Stranger” in 2015 that is comprised of... wait for it... the contents of spit buckets from a wine festival. A little nauseated at the thought? That's fair. But according to Peter Bignell, the owner of Belgrove, people actually drank the stuff and liked it. Some of the distilled spirit was aged for nine months, and some was left un-aged. “The spirit was taken back to the Rootstock festival the next year and sold back to the people who spat it out,” Bignell explains. “Most people liked the un-aged spirit better.”

Associate professor in food microbiology at the University of Tasmania Tom Ross told ABC Radio Australia, "Mostly what you'd be worried about is transmission of microorganisms, germs," he said. "But the heat in the distillation process should get rid of most of those."

The experiment was enough of a success that Bignell was invited to the French wine fair Sous Les Paves La Vigne this May to repeat it. “I had a hard time finding a French distillery that was okay to put that in its alembic,” says festival director Antonin Iommi-Amunategui. “Many [found] it disgusting or far too crazy.” But Distillerie O'Baptiste decided to give it a shot. “The idea behind this project may sound foolish and gross, but first of all, it's a concept, a philosophy,” says Iommi-Amunategul. “We are in a time of emergency where we don't want to waste anything anymore.”

A bonus of sustainable experiments like these is that they often end up reducing overhead, too. Richard Betts, the founder of Sombra Mezcal, is vocal about the toll mezcal production takes on the environment. The physical waste leftover from distilling often goes into the rivers, to the detriment of the fish and villagers who rely on the water as a drinking source. “We're making more mezcal than ever, so we need to work harder at it than ever,” he says. “Ultimately, every producer needs to look in the mirror and ask themselves if they are in it for selfish, short-term gain, or if they want to be a part of something bigger and more meaningful. I'll take the latter.” Some of the practices he’s implemented include using rainwater instead of municipal sources whenever possible, a solar-powered tahona (the traditional stone wheel that crushes the agave), and up-cycling the waste from production into adobe bricks for public works instead of dumping it.

Large-scale manufacturers are doing their part as well. Patron produces over 6,000 tons of compost every year that enriches their agave fields. It was also the first tequila distillery to switch to natural gas as a main source of energy. Jim Beam has joined forces with the Bernheim Arboretum and Research Forest to develop a sanctuary that will help protect water quality and restore natural habitats. In Scotland, Glenmorangie distillery has partnered with Heriot-Watt University to restore the oyster population to the Dornoch Firth, a strait on the east coast of the Highlands region. And Zirkova Vodka, based in Ukraine, is working with the Oceanic Global Foundation to help bars and restaurants implement sustainable practices by eliminating things like plastic straws.

Back in Kentucky, Heron isn't just testing out his leftovers brandy. The distillery has installed a solar panel array to supplement their energy, developed two closed-loop water recycling arteries with the goal of getting to 100 percent recycled water, and planted a monarch butterfly garden that doubles as a stormwater run-off area. Also, visitors who bicycle or use an electric car get discounts. says that the spirits industry recognizes that its future (not to mention the planet's future) depends on these sustainable efforts.

“Most people are divorced from the reality… that the base materials used in winemaking, brewing, distillation are all agricultural raw materials,” he says. “If you understand this, it's very obvious that not only is environmental responsibility a moral obligation, it is a commercial imperative.” Indeed, when it comes to environmental responsibility, Heron isn’t content to “let the mystery be.” For him, and many other distillers, the time for action is now.