That smoky flavor in your glass of scotch? It comes from peat – essentially ancient, decomposed vegetation that forms in waterlogged bogs across Scotland. When burned, this “young coal” releases phenols that infuse barley during the malting process, creating those distinctive smoky notes whisky lovers cherish.

The intensity of peat varies dramatically across scotch whiskies, measured scientifically in phenol parts per million (PPM). These range from completely unpeated expressions at 0 PPM to mild Highland Park at around 20 PPM, all the way to intense Islay drams like Ardbeg at 50 PPM and experimental Octomore releases exceeding 300 PPM – possibly the smokiest whiskies on Earth.

What is Peat and How Does it Work?

Peat forms over thousands of years when plant matter – mostly mosses, grasses, and heather – becomes submerged in waterlogged bogs. Without oxygen, this vegetation only partially decomposes, creating dense layers of dark, organic material that can be cut into burnable blocks.

During whisky production, peat enters the equation at the malting stage. Barley must first be germinated by soaking in water, then carefully dried to halt germination at precisely the right moment. Traditionally, this drying occurred over a peat-fuelled fire, where the rising smoke would bathe the barley in phenolic compounds. These chemicals cling to the grain and survive through the entire distillation process.

Think of peat-like wood chips in barbecue – just as different smoking woods impart distinct flavors to food, different Scottish peat bogs produce unique whisky flavors. Islay’s coastal peat delivers medicinal, maritime notes, while Highland peat tends toward an earthy, heathery character.

Historically, peat wasn’t a flavor choice but a necessity – trees were scarce on Scottish islands, making peat the only practical fuel for drying malt before modern transport and energy alternatives became available.

The Peat Scale: From Light to Heavy

Scientists measure peat intensity using PPM (phenol parts per million) – a laboratory analysis determining how many smoke-derived phenolic compounds have adhered to the barley during kilning. While this measurement occurs before distillation, it provides a reliable guide to the smokiness you’ll experience in your glass.

Unpeated (0-1 PPM): Most Speyside whiskies like Glenfiddich and The Macallan fall here, showcasing fruit, vanilla, and honey notes without smoky interference. Bunnahabhain from Islay surprisingly belongs in this category too, proving not all island whiskies are smoke bombs.

Lightly Peated (1-10 PPM): Springbank (~8 PPM) exemplifies this subtle approach, with just enough smoke to add complexity without dominating other flavors. These whiskies offer an excellent entry point for peat newcomers.

Medium Peated (10-20 PPM): Highland Park (~20 PPM) sits comfortably here, presenting a balanced profile where heathery smoke weaves through honey and orange notes. Bowmore, despite hailing from Islay, also occupies this middle ground.

Heavily Peated (20+ PPM): This is where Islay truly dominates. Laphroaig and Lagavulin (35-40 PPM) deliver medicinal, maritime intensity while Ardbeg pushes beyond 50 PPM. The experimental Octomore series from Bruichladdich has reached an astonishing 300+ PPM, creating some of Scotland’s most intensely smoky drams.

Regionally, Islay remains synonymous with heavy peat, while Speyside and Lowland distilleries typically produce unpeated expressions. The Islands and Highlands tend toward light to medium peat levels, with notable exceptions in both directions.

Popular Scotch Whiskies by Peat Level

• Bunnahabhain – ~2 PPM (practically unpeated in its core expressions)
• Springbank (Campbeltown) – ~8 PPM (lightly peated)
• Highland Park (Orkney) – ~20 PPM (lightly peated with subtle smoke)
• Bowmore (Islay) – ~20 PPM (moderately peated)
• Talisker (Skye) – ~25 PPM (moderate, an obvious smoky note but not overpowering)
• Ledaig (Mull) – ~35 PPM (heavily peated, the peated variant of Tobermory)
• Lagavulin (Islay) – ~35–40 PPM (heavily peated, but often perceived as smoother due to age)
• Laphroaig (Islay) – ~40 PPM (heavily peated, very smoky and medicinal)
• Port Charlotte (Islay, Bruichladdich’s peated line) – ~40 PPM (heavily peated)
• Ardbeg (Islay) – ~50 PPM (very heavily peated, an iconic “peat bomb”)
• Longrow (Campbeltown, Springbank’s peated malt) – ~55 PPM (very heavily peated)
• Octomore (Islay, Bruichladdich special editions) – 80–300+ PPM (ultra-peated experiments, some of the highest ever measured)

Tasting Peat: What to Expect

Your first encounter with heavily peated whisky might be surprising – descriptors like medicinal, iodine, tar, and seaweed aren’t typically associated with enjoyable drinks! Begin with Highland Park 12, where gentle heathery smoke balances honey sweetness, offering an approachable introduction to peat. When ready, Talisker 10 provides a maritime, peppery smoke that’s noticeable without overwhelming.

For the full Islay experience, Ardbeg 10 delivers powerful smoke with surprising balance – expect bonfire, charcoal, and espresso notes. Laphroaig 10, with its intense medicinal character, represents peat’s most polarising expression.

“Peated whisky is like spicy food – what seems overwhelming at first can become addictively complex once your palate adjusts,” explains whisky expert Dave Broom.

The best education comes through exploration: arrange a flight of increasing peat intensity to discover where your preference lies on the smoke spectrum. What starts as challenging may well become your favorite dram.

Read the full article at From Mild to Wild: Understanding Peat Levels in Scotch Whisky