Maker’s Mark has started relying on a new energy source for its Loretto, Kentucky distillery. The distillery is now powered by stillage — the water, grain and yeast waste leftover from the process of making bourbon.

Waste management provider Ecovation installed an anaerobic digestion facility for the distillery. The digestion facility processes the stillage to produce methane and carbon dioxide biogas. The Maker’s Mark distillery was previously powered entirely by natural gas. With Ecovation, the company expects to supply up to 30 percent of their own power needs.

The price tag on the new anaerobic digestion equipment is $8 million and is part of a series of improvements as Maker’s Mark steps up production at the plant from 840,000 cases of bourbon a year to 2.2 million. The company is clearly planning for the long haul: changing over their energy source will make the distillery far more sustainable. While natural gas prices haven’t skyrocketed the same way oil has, it simply isn’t a renewable resource. Worse, Maker’s Mark has to buy more natural gas on a regular basis. The anaerobic digestion facility is essentially a one time cost — the distillery actually saves money on having to dispose of stillage.