Whisky 101: Peat

Whiskey 101: Peat

What role does peat play in the production of whisky?

Most whisk(e)y enthusiasts share a lot of common ground. Whether it’s Scotch or Bourbon, Irish or Japanese, most imbibers share the passion across the wide variety of styles available across the globe.  One of the most polarizing topics in the whisky world, however, is that of “peaty” single malt scotches.  It is often a dividing line that creates fervent disputes amongst whisky drinkers.

Some novice whisky drinkers may have heard the terms “peaty” or “smoky” to describe a whisky and wondered what it was referring to. Many seasoned drinkers may have had peaty or smoky single malts and wondered how the flavor is achieved. These are terms I’ve used working retail plenty of times, but never fully researched the entire process.  I decided to delve into exploring the specifics of peat and the role it plays in Scotch whisky to not only educate myself, but hopefully a few readers as well.

Scotland and the surrounding British isles are full of peat bogs, which are basically wet, marshy, mires that consist of decayed vegetation. These bogs are usually several meters thick and are comprised of a combination of grasses, moss, tree roots, soil and other organic materials.  They are formed over thousands of years, and the decomposed matter becomes tightly compacted as it cultivates and expands.  A general rule of thumb is that the bogs will grow about 1 mm per year. Therefore, if one was 2 meters thick it would have taken roughly two thousand years to form.

Throughout Scotland’s history the burning of peat has been used as an energy source.  The peat is dug up into slices and then stacked to dry for a period of a few weeks. Once dry, the slices form dense briquettes that can be burned as fuel. Peat burns fast and emits and abundance of heat energy from the dead plants. Their use has been widespread throughout history in this part of the world. In many industries they’ve been replaced by more efficient methods of energy production such as coal and electricity.

These two gentleman are digging in a peat bog a few meters thick, and stacking the sliced bricks for drying.

In the whisky realm, the use of burning peat has remained relevant due to the unique flavor it imparts. Most specifically on the whisky producing island region known as ‘Islay’ (EYE-lah). The Islay region is the most well known area of production of peated whisky in Scotland. Its is a windswept island off the southwest corner of Scotland known for its rocky, salty seashore. It’s a small area that is home to 8 distilleries and 3,500 people.

islay-distilleries-mapMost of the distilleries are well known, names such as Ardbeg, Laphroaig, Lagavulin, Caol Ila, Bowmore, and Bruchladdich. Islay is the kind of place where whisky making is done by time-honored traditions, and the old fashioned techniques have not replaced by innovation. The smokey flavors associated with this region’s whisky are a specialty that are highly desirable by many whisky drinkers.

Now, the word “terroir” is one that’s usually associated with wine making.  Essentially, it is the characteristic taste and flavor imparted to a wine by the environment in which it is produced. In whisky-making it is an oft overlooked aspect that can actually play a big role in the final product. Oak, water source, and soil cans significantly contribute to the flavor profile of a whisky. Islay Scotch is a prominent example of the effects of terroir on the resulting product. Peat is often locally sourced, sometimes right on the distillery property.

So how exactly does peat have its effect on the flavor of a whisky? The basic concept is simple: the peat bricks are burned to create smoke that drys the malt that is used to make the whisky. Barley is the only grain used in the production of single malt scotches. The first step in whisky making is called malting.  The barley must be prepared for distillation by sprouting the seeds of the unmalted kernels.  It’s the process of germinating the barley by soaking it in warm water for a period of a few days.  This germination produces the sugars needed for fermentation.

Once the barley sprouts, the germination must be stopped. Drying the damp malt over a peat heated fire in a large kiln funnels smoke into the barley grain. The level of smokiness in the final whisky is determined by the time the barley grain is exposed to the pungent peat smoke during the drying process. If the drying period is 30 total hours, a large portion of that time may be allotted for exposure to smoke. For example, the well known distillery Laphroaig allows 18 of those hours for exposure to the peat smoke.

The barley grain is spread out on the floor of a ‘malting house’. Peat is then burned below and the smoke seeps through the floor, drying and flavoring the grain.

There is a wide range of smokiness from one whisky to the next, and it varies between distilleries. Not only does the length of drying and exposure attribute to the intensity of flavor, but also the types of peat used. There is a distinction all the distillers make in regards to simply drying vs. imparting depth of flavor. Once the peated and smoked barley is dry, it is then milled, mashed, distilled and matured in barrels to create the characteristic peaty whiskeys that people love (or hate).

One byproduct of this exposure to peat smoke are measurable chemicals called ‘phenols’. These phenols are absorbed by the barley during the drying process. The amount of time the barley is exposed to the smoke directly impacts the levels of phenols in the product that ends up in your glass. Each distillery has their own standard, which is measured in Phenol parts per million (PPM). Here’s an informative chart that shows some renowned producers and their specific PPM Values:

Examples of PPM values of some well known distilleries:
(the approximate PPM of their malt is in brackets in increasing value)

  • Bunnahabhain (1–2)
  • Bruichladdich (3–4)
  • Springbank (7–8)
  • Benromach (8)
  • Ardmore (10–15)
  • Highland Park (20)
  • Bowmore (20–25)
  • Talisker (25–30)
  • Caol Ila (30–35)
  • Lagavulin (35–40)
  • Port Charlotte (40)
  • Laphroaig (40–43)
  • Ardbeg (55)

It is said that PPM values below 5 are mostly undetectable on the palate.  Ardbeg is generally regarded as the peatiest available. However, some experimentation has been done recently with special release whiskys much higher than those seen here. The Bruichladdich distillery have made versions of a whisky series called Octomore that have experimented with PPM levels starting over 60, moving to releases in the 160’s and have now achieved one over 200 PPM.

As I said. Peated scotches aren’t necessarily for every drinker. The chart provides a good reference to beginners who want to try a peaty single malt, but don’t want to dive right into Laphroaig or Ardbeg. Most would consider peaty scotches an acquired taste, and working up to the higher PPM whisky may help a newcomer to the category gain some experience and a taste for a very specific style of whisky. And of course, plenty of whisky fans, specifically scotch drinkers, can enjoy both peated and non-peated single malts.

And one last thing to be aware of. If you’re into this style of whisky, or wanting to get into them: Don’t wait too long! Peat, unfortunately is not a renewable resource.  We’ve heard of whiskey shortages in the bourbon world, but apparently peat is running out on Islay. For centuries the extraction and use of peat in production has far outweighed its replacement and growth in the region. Some estimates say it could be completely depleted by the 2020’s.

In the meantime, look for some unpeated malt releases from these distilleries. But don’t panic, there should be adequate replacement sources of peat from other areas of the world. Here’s a few more pictures below. Cheers!

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