Burning Dirt: Why Some Scotch Tastes Like Peat Moss

Scotch whisky obtains its flavors from a variety of sources. The water used by higher-end distilleries is often a closely guarded secret used to competitive advantage. The barley used in scotch whisky production will undoubtedly have an influence, as will the handling between the germination and kilning phases. But some whisky distilleries use the old way and bring you the finest scotches by using a healthy dollop of… dirt.

Yep, that’s why scotch aficionados describe some peaty varietals with words including smokey, earthy, heather, floral, seaweed, antiseptic and… iodine.

Making Scotch Whisky

To know why varietals like Laphroaig taste like burning dirt, it’s essential to know how it (and all the others in the same basic genre) is made.

While you can make “whisky” from other things like corn, wheat, oats or rye, to be a true single-malt Scotch, you must use barley as the base grain. After harvesting the prime ingredient, it’s dried out, so most of the moisture (about 88%) is removed. This makes it easy to store in usable condition while still allowing germination to happen when prompted later.

Next up is the steeping step to start the malting process. After swishing the barley around in precisely controlled 16-degree Celsius water (about 60 degrees Fahrenheit), the barley is moved to drums where cool and most air encourages the germination process to start over several days. This sprouting process breaks down the barley into a form where sugars become accessible during the later mashing phase.

For this conversation, the magic happens at this next step. The germinating barley is tossed into a kiln to heat it and stop the sprouting process. Think fire and smoke. Now, hold that thought; we’ll come right back to it.

To finish the process, the barley is dried, ground up and combined with heated water to make a fairly nasty liquid called wort. It’s this wort, which, after cooling, is mixed with yeast to make a form of “scotch beer.” Think weak barley-based alcohol, which tastes kinda foul. This lower-alcohol-by-volume mix is later distilled into the strong stuff that winds up in the bottles. There’s a lot more to those last steps, but we’re here to talk about burning dirt, so we’ll leave the details of the milling, mashing, fermentation and distillation processes for another story.

Burning Dirt

Let’s return to the kilning stage since we’re talking about why people pay big dollars for booze that tastes like decomposing weeds.

When scotch distillers fire up that kiln to heat and dry the germinating barley, they have to use some sort of fuel for the fire, right? The highlands of Scotland aren’t known for an abundance of forests and firewood, so over the centuries, folks have used dried peat moss for cooking and heating fuel. And barley kilns.

When you set that stuff on fire, most wouldn’t describe the smell as anything you’d buy from Yankee Candle. It’s more like burning bandaids or maybe flavored tires.

What Is Peat Moss?

Imagine grass, weeds, shrubbery, and other assorted greenery growing across vast fields in a moist, rainy climate. Now consider its seasonal death with no one around to rake up the mess. Allow this process to repeat itself over and over for thousands of years, with new rotting vegetation dying, decomposing, and pushing down all the stuff that rotted before. Eventually, you end up with many feet of smelly compost under the current layer of grass or whatever is native to the area. Ipso facto E. Pluribus unum, we’re talking dirt. You might consider this stuff underaged coal. Locals call it peat.

As it turns out, when you’re poverty-stricken, and the area where you live is light on trees for firewood, you figure out you can dig up hunks of this detritus, let them dry for a few weeks and then burn them. Mmmm. Smells delicious. Don’t use it in your BBQ smoker if you want repeat guests.

Well, this is precisely what happened in Scotland way back in the days before microwave cooking. While peat isn’t so much a standard heating and cooking fuel anymore, it is still used to heat those kilns to dry out malted barley. And guess where all that smoke and stink goes? That’s right, into the barley itself, giving “peaty” scotches their unique flavor.

We should note one more variable at play. Consider how different vegetation grows in the hills, plains and coastal areas. The rotting plant flesh acquires unique “flavors” depending on its flora, so different peated scotches will have different smoky flavors. Those coastal peat varietals might even acquire notes of dead fish and seaweed. Yum!

One more thing. If you’re a peat-head, don’t worry about running out. Somewhere over 20 percent of Scotland is covered with the stuff.

Dirtless Scotch

All scotch whisky isn’t dirty. Much of what you find in the liquor store aisles is made like other spirits, relying on the characteristics of the water supply and barley for each brand’s distinctive taste. But a subset of scotch distilleries treasure those childhood memories of cooking mud pies and go all out to bring you that, um, unique flavor profile peat-heads so enjoy.

I’m poking some fun here, but in all seriousness, a “peaty” scotch can be delectable.

Of course, it’s an acquired taste.

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