Maine’s booming craft beer scene is helping drive demand for traditional wooden barrels.

The state’s growing ranks of brewers are expected to produce 39 percent more beer next year compared with 2017, according to February figures from the Maine Brewers’ Guild and the University of Maine. And about 42 percent of those breweries are working with Buxton-based River Drive Cooperate & Millwork, which refurbishes, resells and distributes barrels it gets from whiskey, rye and winemakers throughout the world.

The brewers are embracing the ancient technique of barrel aging, which allows them to create unique beers that can fetch a higher price.

Since the aging process can take between six months and two years, not all of them are offering the barrel-aged beer yet, “but barrel aging has been trending up in the past two years,” River Drive founder Matt Albrecht said.

Since it started processing and distributing barrels in 2012, River Drive is barely keeping up with demand. Last year it sold 5,900 barrels and expects to sell 10,000 by the end of this year. The company plans to expand twice in the next two years, and may add a second building after that.

“We’re building a $750,000 expansion, and have gone from two to 10 employees in the past 12 months,” Albrecht said.

Aging beer in previously used barrels can create unique character and styles using yeasts, tastes leached from the barrel wood and flavors left over from other spirits.

Fresh oak barrels typically are first used to make the strong liquors, which take most of the tastes out of the wood that would be too strong for beer drinkers. The used barrels then are refurbished, leaving a hint of rye and other flavors that can be soaked up by beers.

Albrecht buys barrels everywhere, and resells them to clients from California to Europe.

His barrels run about $150 to $200, plus shipping, but rare and unique ones can sell for more than $500, he said.

But the return on investment is substantial. Breweries can charge $17.99 for 750 milliliters of beer aged in barrels compared with $9.99 for beer aged in stainless steel containers.

Brewers that age beer in barrels include Allagash Brewing Co. and Oxbow Blending and Bottling in Portland, Barreled Souls Brewing in Saco, Orono Brewing Co. at its Bangor taproom and Bear Bones Beer of Lewiston, which plans to use the basement of its second location in Bridgton to expand its barrel-aging operation. Bangor newcomer Mainiacal Brewing Co. also ages beer in barrels, and plans to open in late September.

“There’s an increase in barrel aging now,” said Orono Brewing brewmaster Asa Marsh-Sachs, whose company plans to expand its use of the process. “With barrel aging, you have more in your tool box from making sour and wild beers and blending barrel to barrel.”

The upcoming Beer Meets Wood event on Sept. 23 in Portland is expected to have the largest collection of wood-aged beers on the East Coast, including more than 200 beers from 20 states and Belgium.