Peat, Phenols, and PPM in Scotch Whisky
Peated Scotch whisky is one of the most polarising and fascinating styles in the whisky world. Understanding what peat is and how it creates those iconic smoky flavours is key to appreciating peated Scotch whisky.
What Is Peat?
Peat is partially decomposed organic matter — primarily sphagnum moss, heather, and sedges — that has accumulated over thousands of years in boggy, waterlogged conditions across the Scottish Highlands and Islands. Scotland has vast peat deposits, particularly on Islay, Lewis, and in the Northern Highlands.
How Peat Gets Into Whisky
Peat is burned during the kilning stage of malting. When damp peat smoulders, it produces dense aromatic smoke that permeates the malt, depositing phenolic compounds — particularly guaiacols — into the grain. These survive mashing, fermentation, and distillation to impart the characteristic smoky flavour to the finished whisky.
Phenols and PPM Levels
Unpeated (0–2 PPM)
No smoke. Classic Speyside and Lowland style. Glenlivet, Auchentoshan.
Lightly Peated (10–15 PPM)
Subtle smoke, barely perceptible. Highland Park 12, Balvenie.
Medium Peated (20–35 PPM)
Noticeable smoke character. Bowmore 12, Ardmore Traditional Cask.
Heavily Peated (35–50 PPM)
Intense smoke and iodine. Laphroaig, Lagavulin, Ardbeg.
Super Peated (100+ PPM)
Extraordinarily high phenols. Bruichladdich Octomore range regularly exceeds 100 PPM in the malt.
PPM levels are measured in the malt before distillation. Phenol levels reduce significantly during distillation and maturation — so the final whisky PPM is lower than the malt PPM figure.