Well-Oiled Remedy

Abstract

The process for making Scotch whisky uses three ingredients: water, yeast, and a grain, primarily barley. About 10% of the output is spirits, and the rest is by-products. Those spirits can’t be called Scotch whisky until they age in oak casks—in Scotland—for at least three years. The by-products are residual solids called draff and a yeasty, copper-contaminated liquid known as pot ale. They are usually spread on agricultural fields, turned into low-grade animal feed, or discharged into the sea. The Scottish start-up Celtic Renewables is looking to take draff, pot ale, and its own microbe to produce acetone, 1-butanol, and ethanol. Along the way, the small company hopes to revitalize the once widely used ABE fermentation process, so-named after the three chemicals it makes. Draff and pot ale “have no commercial value, and in the modern context they represent a disposal issue,” says Martin Tangney, founder, president, and chief scientific ...