Green Credentials

The Scottish whisky industry is a huge consumer of energy and much of this goes into heating water. Water has one of the highest specific heat capacities known at about 4200J/kg/°C - in simple terms this means it takes a lot of energy, relative to other substances, to heat water.

Hydrogen has the highest specific heat capacity of any compound or element at 14,300J/kg/°C and this is why, despite its flammable and explosive nature, it is used to cool electrical generators in power stations.

Distilleries already use heat exchangers to take energy from waste products to pre-heat incoming water for the next mash. However, energy is no longer cheap and no longer considered a waste product. Shareholders and customers alike are demanding greener credentials and there's a strong focus on re-using waste energy to reduce primary fuel consumption and to increase corporate reputation.

According to Zero Waste Scotland the whisky industry produces 1,600,000,000ℓ of pot ale (the waste after the first distillation in the wash still) and 500,000 tonnes of draff (the spent barley after mashing) each year. For years, draff has been sold or given to local farmers to feed their stock. Pot ale on the other hand is non-toxic and has been run to waste or discharged into the sea. Now though, some distilleries are feeding both waste streams into anaerobic digesters where biogas (containing methane and carbon dioxide) is produced and used to generate electricity or process steam for the distillery.

Easy-win changes and adaptations were the first to be implemented and now the more difficult ones are being addressed and may only give small savings. One, for example, is keeping the pot ale in the wash still until just before it's needed for the next wash. This preserves some of the heat and can contribute to a faster start-up of the next batch.

Bruichladdich has dispensed with the metal tin and redesigned their iconic aqua colour bottle. The old style bottle was an industry standard design but the new shape is 32% lighter and made from 60% recycled glass.

Chivas Brothers has incorporated mechanical vapour recompression technology with its existing thermal vapour recompression to recycle close to 100% of the steam produced in its falling film condenser - a type of heat exchanger.

Success Stories

Oak leaf and acorns

Diageo-owned Glendullan distillery produced 6,000MWh of thermal energy from its digester in its first year of operation, enough to reduce its conventional fuel bill by 25%.

Diageo's Roseisle distillery sends its waste energy to two nearby malting plants.

Bruichladdich distillery uses surplus waste energy to heat its visitor centre, bottling hall and offices.

Bowmore distillery uses surplus waste energy to heat the adjacent community swimming pool.

Inver House's Balmenach distillery has a digester that treats about 130m3 of whisky by-products to produce 2,000m3 of biogas per day, which it burns in a CHP engine to supply power and heat for its own use.

Diageo's Dalluaine distillery uses a digester to create biogas, which is then used in a Perkins engine to generate 40% of the electrical demand for the site.