Circular use of feed by-products from alcohol production mitigates water scarcity

The distillery sector is among the biggest industrial water user in the United Kingdom (UK) and simultaneously delivers valuable by-products traditionally used for cattle feed, but in recent years increasingly for bioenergy generation. Our research provides new insight into these two aspects of alcohol production by 1) presenting the first water scarcity footprint of Scottish single malt whisky, and 2) comparing potential avoided water scarcity impacts through the use of by-products to replace different feeds and energy carriers. We applied Life Cycle Assessment, including a water scarcity footprint (AWARE methodology) and carbon footprint, using primary data from a Scottish whisky distillery. By-products used for feed were considered to replace imported soybean meal from the Americas or rapemeal from Europe combined with UK grown barley to balance protein and metabolisable energy substitution. Alternative by-product use for biogas production replaced conventional heat and electricity generation, or transport fuel with the digestate substituting mineral fertilisers. The water scarcity footprint of 1 litre of pure alcohol is 0.79 m ³ world eq., with the majority of water used for cooling, highlighting a hotspot for water conservation. The carbon footprint is 4.4 kg CO ₂ eq., predominantly caused by heating with gas oil. By-product use as animal feed, replacing soybean meal and barley, offsets up to 47% of the water scarcity footprint and 32% of the carbon footprint of alcohol production. Using by-products for bioenergy generates smaller offsets. Water reuse and heat recovery measures should be investigated as priorities to reduce the environmental footprint of whisky. Feeding all cereal based by-products from UK potable alcohol production to cattle could save 370 M m ³ world eq., or 37% of the UK's water scarcity footprint attributable to imported soy feed.