What Is Peat, Anyway?

Peat is responsible for scotch’s distinct smoky flavor, that palate-tingling fire that drives whisky fanatics to spend ridiculous amounts of money on booze. The Islay region is particularly known for highly-peated scotch, with distilleries like Laphroaig, Ardbeg and Lagavulin delivering the unbridled flavor of the small Scottish island to drinkers all over the world. But what exactly is peat, and why does it matter?

Where Does Peat Come From?

Before being used in whisky production, peat can be found in a bog. These bogs—also known as peatlands or mires—are massive fields built up over centuries. Bogs grow at about 1 millimeter per year, so an average 3 meter deep bog was created over the course of 3,000 years. The peat itself, a spongy material, is comprised of decayed plant matter—mostly moss.

Peat’s Burn

Peat’s incrementally slow formation ironically contrasts its incredibly fast burn rate. Igniting the dried terf releases an immense amount of heat, something early peoples in the region put to great use to stay warm. The flammable muck is a relative of coal, and while it burns much faster than its more recognizable sibling, it’s still a slow burn compared to wood.

How Peat Is Harvested

Traditionally, peat is cut from the earth by hand, and the resulting “sod” is packed into briquettes to dry. In the last century, however, global demand for peat as a fuel source has given rise to large scale, industrial extraction using heavy machinery, which resembles crop harvesting more than coal mining. Peat accounts for 2 percent of the Earth and is not a renewable resource, meaning it could become a scarce commodity in the years to come.

How Peat Is Used in Distilling

While there is a bit of peat in the water with which whisky is distilled, and peat is used to heat the stills, scotch’s smoky flavor comes from peat’s influence over the barley that makes up the whisky mash. After the barley spends some time on the malting floor (during which the starches in the barley are converted to soluble sugars that can be distilled), distillers halt the germination process by heating the grain up in a kiln. This is where the peat comes in. Distillers smoke the barley with the peat, imbuing it with delicious earthy, campfire flavors, and transforming it into malt.

The Difference Peat Makes

The precise flavors peat imparts to whisky depend on the specific plants that gave up their lives to become fuel for our liquid enjoyment. According to Whisky Science, burning sphagnum (the peat moss that makes up most peat) releases chemical compounds called phenols that are absorbed by the barley and create the smoky characteristics we know and love. Woody plants in the peat-mix contain a greater percentage of other aromatic compounds like syringol and guaiacol, which create different flavors. The mix of materials within the peat is reflected in the flavors it imbues into the whisky.

Phenol levels are often used to compare scotches. Understanding a scotch’s PPM (Phenol Parts per Million) can help set your expectations for how much smoke you’re going to get before even popping the bottle. For example, Springbank has a PPM of around 7 to 8 (lightly smoky), while Talisker hovers between 25 and 30 (fairly smoky), and Ardbeg is all the way up at 55 (seriously smoky).

Now that you know what peat is, it’s time to taste its delicious effects for yourself in one of these fantastic, smoky scotch cocktails.