Peat in Scotch Whisky
The flavour peat bestows on a malt whisky is unrivalled, we find it to be more of an experience than a taste. The smoke seems to fill and whirl around the palate, the aroma transports us back to a B&B in the Highlands, cosied up by the fire sipping our favourite Scotch. However, the fascination of peat lies beyond just taste. Keep reading as we explore where peat comes from, it’s environmental impact and the science behind its famous smoky flavour. Our Peat in Scotch Whisky blind tasting experience explores the impact of peat in Scotch whisky with six diverse single malts. Choose a gift set or sharing box and we’ll provide a complete blind tasting experience you can enjoy from home!
Peat is an accumulation of partially decayed vegetation and other organic matter that builds up where the climate is wet and the land is poorly drained—which pretty much describes large swathes of the highlands and islands of Scotland! Water that has percolated through peat bogs may only have a subtle influence on the aroma and taste of whisky, but the use of peat to fuel the drying of the kiln certainly has a major impact.
In areas where it is plentiful, and peatlands cover about 20% of Scotland, peat would have been cut and stacked in May and June and then dried in open air until ready to burn. Even after many months, naturally dried peat never becomes a particularly efficient fuel and, when burnt, would produce a pungent smoke which rises with the hot air through the damp malted barley in the drying kiln.
In this way a wide range of phenolic compounds in the smoke end up being absorbed by the grain and, as detailed in Paul Hughes book The Science and Commerce of Whisky, different compounds impart different flavours and aromas;
- 4-Ethylguaiacol - Smoky, meaty
- Phenol - Carbolic
- 2-Methylphenol (o-cresol) - Musty, Medicinal
- 4-Vinylguaiacol - Spicy, Clove
- Dimethylphenols (Xylenols) - Medicinal, Sweet
Crucially, the balance of phenolic compounds in the smoke depends on the composition of the peat, and this varies from place to place. Diffords Guide to Single Malt Scotch Whisky Production provides an excellent summary;
“The seaweed, tar and iodine so typical of Islay malts are partly due to decomposed marine vegetation and sea salt in the island’s peat. The peat on the Orkney Islands is composed almost entirely of heather so imparts Orcadian malts with a heathery, gentian-lik smokiness. Highland peat varies again according to location but contains more tree lignin so tends to impart a more wood-fire like smokiness”
Bruichladdich’s Octomore Virgin Oak 10.4, peated to 188ppm, is included in our Luxury Tasting and Peat in Scotch Whisky blind tasting collections.
As a general rule, the longer the malted barley is exposed to peat smoke, the smokier the whisky will tend to be. The Bruichladdich Octomore 6.3 Islay Barley is the worlds peatiest malt, with a whopping 258 phenol parts per million (ppm). To put that into context, the famously peaty malt Laphroaig has a phenol level of 45ppm!
One problem is that peat is effectively a non-renewable fuel which emits a large amount of CO2 when burnt (worse even than coal when relative to the energy in produces). The bogs from which peat are cut are also important carbon sinks. The UK Centre for Hydrology and Ecology estimates that they store 3.2 billion tonnes of carbon in the UK alone.
Today, peat is no longer used as the primary fuel to dry the grain, though it is burnt specifically to infuse the grain with phenols. The use of modern drying kilns means that only a tiny fraction (perhaps 1%) of peat extracted from Scottish bogs is used in the whisky industry—the vast majority being used in horticulture and domestic fireplaces.
Nevertheless, addressing peatland degradation has become part of the industry’s emerging focus on environmental sustainability. Thus, in addition to peatland restoration, the Scottish Whisky Association, the Scottish government and the Green Investment Bank have begun to work together to reduce carbon emissions and promote a greener industry; focussing on water efficiency, green energy, recyclable packaging and reaching a ‘0% waste to landfill’ target.
In the next article of our Exploring Whisky blog series we look at the process of milling, and the infamous Porteus Malt Mill, that worked so well, the company eventually went out of business!
Further Reading;
The Science and Commerce of Whisky - Paul S Hughes, Ian Buxton, 2014
Diffords Guide to Single Malt Scotch Whisky - Diffords Guide
Peat Bogs - The UK Centre for Ecology and Hydrology
Peatland Restoration - The Scottish Whisky Association