But using crops was costly, and oil provided an inexpensive alternative. Tangney’s goal was to find a cheap base material to make biofuels commercially viable — as well as more sustainable.
The startup uses a process known as acetone-butanol-ethanol (ABE) fermentation in which bacteria break down the sugars in the whisky draff and pot ale into acids. They in turn are further broken down into solvents such as butanol and ethanol, which can be added to petrol or diesel to power a car. Celtic Renewables has demonstrated its fuel, driving an unmodified Ford on Scottish roads using 15% biobutanol made from whisky.
Tangney says his fermentation process isn’t limited to whisky by-products, and could use waste from other food sectors such as dairy. “That’s where we see ourselves as adding value,” he says.
A viable solution?
As aviation and other industries look to biofuel as a quick solution to decarbonize, Smith warns that there are “huge trade-offs and impacts on biodiversity, carbon storage, and food security,” depending on the raw material.
However, fuel made from “genuine waste” such as whisky by-products is “probably the best possible kind of biofuel” she says, as it avoids these problems. Tangney has commissioned an independent life cycle analysis of his product to evaluate its environmental benefits, to be published later this year.
Instead, the transport sector should emphasize reducing demand, says Smith. “That makes it much easier to supply the rest of our transport needs from sustainable sources, whether that’s renewable electricity or biogas or liquid biofuels,” says Smith.
Beyond waste-based fuels
Whisky waste can be used to create more than biofuels. The solvents from its fermentation can be used as an alternative to oil in plastics, cosmetics, pharmaceuticals, clothing and electronics, says Tangney.
Celtic Renewables has raised more than £40 million ($52 million), with backing from private investors, government grants, and crowd funding, in addition to support from Napier University, which remains a shareholder.