Bourbon is a multi-billion-dollar market, but the American barrel-aged whiskey also produces a lot of wasted grain at distilleries. Chemists at the University of Kentucky developed a method to transform that stillage into electrodes and used those electrodes to build supercapacitors with energy storage capacity on par with existing commercial devices. They presented their work at a meeting of the American Chemical Society in Atlanta, Georgia.
US distillers began making bourbon in the 18th century, particularly in Kentucky, but it really took off commercially, in terms of consumption and exports, after World War II. Legally, a whiskey can only be sold as bourbon if its mash is composed of at least 51 percent corn, with any other cereal grain (usually rye and barley) making up the remainder.
The grain is ground up and mixed with water, and mash from a previous distillation is added to create a sour mash. The addition of yeast launches fermentation, after which the mash is distilled to a clear spirit called "white dog." That spirit is poured into charred new oak barrels for aging of at least two years. It's the caramelized sugars and vanillin in the charred wood that give bourbon its distinctive dark color and flavor. The barrels are never reused for bourbon, typically being recycled for making barrel-aged beer, wine, and even barbecue and hot sauces.