Researchers say stronger wash could lower distillation energy demand and liquid residues, but effects on yeast performance and flavour need further study.
By Eilidh GrantEngineering & Infrastructure Reporter· Scotland
Heriot-Watt University researchers have found that raising wash strength to 14% ABV could reduce both energy consumption and carbon emissions in Scotch malt whisky production by about 16% per litre of pure alcohol. The findings, reported on 15 October 2026, concern changes to the production process rather than a distillery construction project.
The study examined moving from a typical wash strength of approximately 8% ABV to a range of 10–14% ABV. Dr Shiwen Zhuang, from the university’s International Centre for Brewing and Distilling, led the work.
Researchers also calculated substantial reductions in the liquids left after distillation. Pot ale volumes could fall by 55%, while spent lees volumes could drop by more than 30%.
Wash is the beer-like liquid produced when yeast ferments wort. The wort is prepared by mashing malted barley with hot water, and the resulting fermented wash goes into a wash still for the first distillation.
Pot ale is the nutrient-rich residue from that first distillation. Spent lees remain after the second distillation, making them a separate stream for distilleries to manage.
The research was undertaken by Zhuang, Dr Jane White and Professor Chris Boulton. Their work appeared in the Journal of the Institute of Brewing.
Zhuang said the findings had different implications for established operations and new developments. Existing distilleries might be able to raise output without adding fermentation capacity, while new or expanding sites could achieve equivalent production with smaller equipment and reduced processing volumes.
White identified potential savings beyond energy consumption. She said reducing pot ale and spent lees volumes could lower the cost of handling, transporting and treating those residues, while retaining concentrations of valuable materials suitable for recovery and reuse.
The researchers cautioned that increasing wash strength presents unresolved production challenges. Obtaining higher concentrations of fermentable sugars could require changes to mashing methods.
Further investigation is also needed into yeast performance, flavour development and effects across the wider production process. The source gives no timetable for that work or for commercial adoption.
The findings connect fermentation strength with energy demand, equipment sizing and residue management. For distillers and project teams, the reported potential extends beyond emissions: existing fermentation capacity could support more output, while new developments could use smaller equipment. Those remain potential benefits rather than an established operating solution, with the researchers identifying unresolved questions around mashing, yeast performance and flavour.