Producing a stronger alcoholic liquid before distillation could make Scotch malt whisky production more efficient by cutting energy use, carbon emissions and volume of liquid residues, researchers at Heriot-Watt University have found.
The study, which was led by Dr Shiwen Zhuang from the University’s International Centre for Brewing and Distilling, is the first to measure how increasing wash strength from the industry standard of around 8% alcohol by volume (ABV) to between 10% and 14% ABV could affect the efficiency and environmental impact of Scotch malt whisky production.
The wash is the liquid created after the fermentation of a sweet cereal-based liquid known as wort. Yeast is added to the cooled wort, converting the sugars into alcohol and producing a beer-like liquid called wash.
The wash is then transferred to the wash still, where the first stage of distillation concentrates the alcohol and begins refining the flavours that will ultimately define the whisky.
According to Dr Zhuang and Dr Jane White, assistant professor at Heriot-Watt’s International Centre for Brewing and Distilling and co-author of the study, by using a model that reflects real-world fermentation and traditional two-pot distillation, increasing wash strength to 14% ABV could reduce energy use and carbon emissions by around 16% for every litre of pure alcohol produced.
This approach could also cut pot ale volumes, the nutrient-rich liquid remaining after the first distillation, by 55% and reduce spent lees, the liquid remaining after the second distillation, by more than 30%, significantly lowering liquid residues from the distillation process.
The findings, the team said, come as the Scotch whisky industry works towards net zero targets and looks for new ways to improve efficiency while maintaining production levels.
Dr Zhuang said: “This study highlights the potential environmental and operational benefits of stronger wash. These benefits could be achieved in different ways.
“Existing distilleries may be able to increase output without expanding fermentation capacity, while new or growing distilleries could produce the same amount of whisky using smaller equipment and lower processing volumes.”
And Dr White added that the study also identified “potential economic benefits”.
She said: “Lower volumes of pot ale and spent lees could reduce handling, transport and treatment costs, while maintaining the concentration of valuable materials that could be recovered and reused from these residues.”
The authors note that challenges remain before stronger wash can be widely adopted. Producing higher levels of fermentable sugars may require new approaches to mashing, while the effects on yeast performance, flavour development and the wider production process need further study.
Despite these challenges, the findings to date provide a useful framework for exploring ways to make Scotch whisky production more sustainable.
The research was published in the Journal of the Institute of Brewing and was carried out by Dr Shiwen Zhuang, Dr Jane White and Professor Chris Boulton.
