Peat is partially decomposed organic matter — primarily ancient plant material — that has accumulated in waterlogged bogs over thousands of years. In Scotland, particularly in Islay and the western islands, peat is harvested from these bogs and burned as fuel. When malted barley is dried over a peat fire, the smoke impregnates the grain with aromatic compounds called phenols. These phenols carry through fermentation and distillation into the final whisky, producing the characteristic smoky, medicinal, brine-like character of peated Scotch. The peat itself takes 7,000+ years to form — making peated whisky a uniquely traditional product. With 117 mentions across 4 categories on LivCheers, peat is concentrated in single malts, Scotch, and Indian peated whisky.

Peat character varies dramatically by region. Islay peat (the most famous) is heavily marine-influenced — producing whisky with brine, iodine, and seaweed character alongside smoke. Highland peat is more earthy and less maritime. Indian peat (used in Indri, Paul John Peated, Amrut Peated) has its own character — often more spice-driven and less marine than Islay. The peat character is measured in 'phenol parts per million' (ppm). Most heavily peated Scotch sits at 30–50 ppm; Octomore can exceed 200 ppm. Lightly peated whiskies use restrained peat character; smoke-bombs like Ardbeg Supernova aim for maximum impact.