Most of the fuel, he added, will be comprised of the draff.

Their diet is topped up with draff, a by-product of the whiskey industry that's a great source of fibre and protein.

Tangney's ABE process involves blending pot ale and draff - two residues that make up 90 percent of the distillery output.

Scottish distilleries produce around 750,000 tonnes of draff and two billion litres of pot ale every year.

DRAFF: An Exhibition promises to lift the lid on the performing arts scene in Dublin.