A list of breweries currently open in Louisville and Southern Indiana.
Bailey Loosemore/Courier Journal

In warehouses across Kentucky, more than 6.6 million bourbon-filled barrels await their perfect age.

And around the world, a horde of craft brewers are waiting, too, itching to get their hands on the bourbon-soaked wood.

The brewers need the barrels if they want to keep up with the growing demand for bourbon barrel-aged beers — a style that was once considered a specialty and that’s now almost become a requirement for any brewery opening anywhere in America.

More bourbon barrell age-beer: The 5 best bourbon barrel-aged beers in Kentucky

In the past three years alone, the Brewers Association reports, sales of barrel-aged beers have increased 20 percent.

“Today, almost every new brewery that starts does so with a barrel program as part of their business model,” said Matt Simpson, owner of the Beer Sommelier, a consulting company in Atlanta.

While the demand could pose a problem for a brewer in, say, Wyoming, brewers in Kentucky have formed close relationships with distillers that are angling them toward the front of the barrel-aged craze.

Need proof? Drop in on this year’s Kentucky Craft Bash, where 28…