Peat in whisky is divisive – both in terms of its intense flavour profile, but also its sustainability. It has long been used in Scotch whisky, adding complexity to the region’s spirits, but has – over the last two decades – been thrust into the limelight.
Essentially, peat is baby coal – decomposed organic matter, in particular sphagnum moss, that takes thousands of years to form. Historically, these peatlands – wetlands such as bogs and fens – were used for fuel, especially where other energy sources weren’t readily available. Slabs of peat, cut out of the ground and left to dry, were burnt, valued for their ability to (like coal) smoulder steadily. Peat would have originally been used to heat pot stills, giving off intensely scented smoke that distillers eventually looked to capture.
Today, energy sources are largely more sustainable, and peat is used in significantly smaller volumes in the kilning process. After the barley has been malted, it is kilned (essentially dried). For peated whiskies, this is done (at least in part) over a peat-fed fire, so that the barley picks up the flavours from the smoke. This barley is then milled, mashed, fermented and distilled to produce the whisky, with the peat smoke lending flavours that range from soot, smoke and asphalt to seaweed and iodine.
Peatlands have been put in the spotlight with climate change, given their incredible capacity to hold carbon – and release it. As a NatureScot report (2023) states, “Although peatlands cover less than 3% of the world’s surface, it is estimated that they store double the amount of carbon held in global forest biomass and more than 30% of the total global soil carbon store (Bonn et al., 2016). Peatlands make up some 9.5% of the UK’s land area with an estimated carbon store of over 3,200 million tonnes, of which 1,600 million tonnes are estimated to be in Scotland (Bonn et al., 2016).” But while they have an impressive ability to lock away carbon, once peatlands are damaged they release some of that carbon – and the same report estimates that degraded peatlands account for circa 13% of Scotland’s carbon emissions. (It’s worth noting that the same institution – then known as Scottish National Heritage – came under fire in 2020 for its agreement with Diageo, allowing for unlimited peat extraction on Islay.)
Peat accumulates at a mere 1mm a year, so it’s easy to see why peat extraction is a hot topic. Protecting and restoring Scotland’s peatlands are firmly on the national agenda, and in 2020, the Scottish government announced £20 million earmarked for restoration, with a commitment to invest more than £250 million by 2030. Unsurprisingly, it’s put Scotch whisky’s use of peat under the magnifying glass. In reality, a fraction (just 1%) of Scotland’s peat goes to the spirits industry – with horticulture the main culprit.
As Bruichladdich’s Head Distiller Adam Hannett says, however, it has provided “a great lens to look at what we’re doing with peatlands”. For him, “It’s about responsible extraction.” Bruichladdich’s production director is also looking at restoration projects with local farmers. In 2021, two giants of the industry announced significant projects – one from Diageo’s Johnnie Walker, partnering with the RSPB to repair wetlands, and a more ambitious pledge from Beam Suntory, with its Peatland Water Sanctuary Initiative. The project aims to restore twice the volume that the company harvests for use in whisky production, with $4 million invested by 2040. Some producers – such as Nc’nean – have sworn off peat totally, while others are moderating usage, or looking for alternatives.
In Sweden – where peatlands represent up to 20% of the entire land area, Mackmyra’s Blender Lii Johnson explains how there is strict regulation around their usage. They are one of a growing number of producers looking to use peat as another way to explore their terroir. As few producers malt and kiln their own barley today, often this is shipped from Scotland (in turn adding to distilleries’ carbon footprints). At Mackmyra, they instead use Karinmossen – local peat, harvested around 40km south of the distillery – seasoned with juniper twigs. She estimates they use a mere 0.1% of the peat bog, bringing in around 30 cubic metres per year.
Johnson feels that it is the juniper in the Karinmossen, along with the small twigs they add (picked from the woods around the distillery), which give a light citrus, almost medicinal note to their peated malts. In Seattle, Westland has pioneered using local peat, and a process with a backhoe to keep the bog intact and limit their carbon footprint. Co-Founder and Managing Director Matthew Hofmann feels the local peat brings Mezcal-like aromas to their peated whisky, Solum.
This quest for sustainability, combined with emphasis on the concept of terroir in whisky, has had interesting results at distilleries around the world. In Minnesota, Brother Justus sources peat from the Boreal Forest and has trademarked a cold-peating process to produce more delicate aromas. Tasmanian distillery Lark looks to Browns Marsh for its peat (around one cubic metre a year) and has had the International Mire Conservation Group confirm that it is having zero impact on the marsh. Others are looking to use alternatives – New Zealand’s Thomson Whisky uses manuka, while Archie Rose has looked to Australian hardwoods and, perhaps most distinctively, Iceland’s Eimverk sources sheep dung from local farms in lieu of peat.
As we’ve touched on, however, it’s not just what is used to peat malt – but how it’s used, that impacts the flavour of the final whisky. “Duration, in my opinion, is the key,” says Mackmyra’s Johnson, emphasising that it is how long the barley spends in contact with the peat smoke that influences the level of peatiness, while it is only the type of peat (or peat alternative) that will effect the nature of the peat flavour. She explains how whether the barley is peated pre- or post-break is also important: it’s most common to do pre-break, as if it is done post-break, when the barley is largely dry on the surface, it doesn’t pick up phenols – the compounds that produce peat’s smoky flavours. For Mackmyra’s peated barley, it is kilned for one day with peat and then for a second day just with hot air.
There are other factors too however – with fermentation times and cuts often a focus. While longer ferments are generally thought to engender complexity, shorter ferments preserve phenols. There are three factions to a still run – the foreshots, heart and feints. The foreshots and feints, the liquid that runs off first and last, are generally discarded, and the cuts between these determine the character of the heart. Phenols generally come late in the distillation process, so later cuts can be preferential when looking for peat character. For Mackmyra’s Extra Rok 2.0 – an extra-peated malt, they do shorter ferments and a later cut, to preserve the phenols.
It's become fashionable to talk about “ppm” in peated whisky – parts per million (perhaps familiar to wine lovers as the same term that is used for sulphur levels), to measure the level of total phenolic compounds. It’s perhaps unsurprising that the compounds are the same as those for smoke taint, including guaiacol and 4-methylguaiacol, for example, but while in the world of wine these are avoided, distillers of peated whiskies have competed to produce the spirit with the highest. This race to make the peatiest whisky possible was arguably inspired by Compass Box’s Peat Monster (first produced in 2003), building to and culminating with Bruichladdich’s Octomore 8.3 (released in 2017) – a whisky with a remarkable 309ppm, the highest level measured to date (compare this to the first Octomore release which had 131ppm). In this frenzied period, Ardbeg’s Dr Bill Lumsden even buried a barrel of peated whisky in a peat bog (which was released as an NFT in 2022, Ardbeg Fon Fhòid). But while one number is an easy way for whisky drinkers to grasp how peaty a spirit is, not everyone believes it’s helpful.
“We don’t like to talk about those numbers,” says Johnson. She explains how ppms are somewhat farcical, in her view. When the reading is taken varies from distillery to distillery, and therefore provides something that is almost impossible to compare. While most are taken at the mashbill stage, if you are later blending, it’s an estimate at best. Not only that, but the make-up of the phenolic compounds will influence how peaty one 100ppm whisky is versus another 100ppm whisky. For Mackmyra, their pure peated malt sits at around 300ppm, but the mashbill for their peated and extra peated whiskies are respectively around 70 and 140ppm, Johnson reluctantly tells me. The level of phenols can also vary significantly between batches of barley – and at Mackmyra they aim to combat this by doing one kilning a year, distilling all their peated whisky at once and blending the batches to create a consistent product.
It's almost for this exact reason that Bruichladdich created Octomore, Head Distiller Adam Hannett explains. The project’s numbered releases have significantly different levels of peatiness, and were a project inspired by their curiosity to see how far they could push the peat level, as well as their partnership with Bairds maltings, who had batches of barley with irregular phenol numbers.
Although peat is intrinsically associated with Islay’s malts, things aren’t as clear-cut today – and as Hannett says, “You can’t categorise flavour by region”. Islay-based Bruichladdich produces both peated and unpeated whiskies. Originally the distillery made heavily peated malts, switching to unpeated styles in the 1960s, and today makes both. Its Port Charlotte brand was first conceived to capture what Bruichladdich would have been like in the old days, as a heavily peated malt. Intriguingly, Bruichladdich briefly tried using Islay peat, however found that they couldn’t get the phenol levels as high. Hannett highlights that another element in phenol levels is the depth the peat is cut from – with lower levels having more vegetation and therefore more phenols.
For Bruichladdich, when they’re looking for an overtly peated spirit, the quality of the underlying spirit is key – working with the right barley and fermentation times, for example. While peated malts might be thought of as heavy, oily and medicinal, they try to avoid this character. He deliberately won’t delay making a cut in the name of phenols, with that decision based on quality – and the result, he feels, is that, “The essence of the peat smoke is light – it’s barbecued.” For him, it’s about the balance between the peat character and everything else.
For blending specialists, House of Hazelwood, peated whisky “is a tool in our arsenal we can use to build a complex blend”, says Eilidh Muir from their Whisky Blending Team. She emphasises that using peat doesn’t necessarily equate to a smoky whisky, but can contribute something to a blend that is much harder to pin down – but something you’d notice if it wasn’t there. “A whisky dominated by a single flavour is often too one-dimensional,” she says – they too are looking for that fine balance.
Peat is just one element that can be used to shape a spirit – and there remains a certain amount of mystery to its influence. The sustainability question isn’t going away, but – as Bruichladdich’s Hannett says, “I don’t know what the solution is at the moment… but we’re looking for one.” As producers look for an answer, they’re pushing boundaries – experimenting with local sources and alternatives – something that will only benefit whisky-lovers, and the environment.
