Peat

Peat is an accumulation of partially decomposed plant material, especially mosses, sedges and other wetland vegetation, that builds up in waterlogged, oxygen-poor environments. It is brown to dark brown, soft, spongy and fibrous, and holds large amounts of water.

Strictly a soil and organic deposit rather than a true rock, peat is nonetheless the first stage in the formation of coal and is studied as a sedimentary deposit. It often preserves recognizable plant fragments and, in special cases, remarkably intact organic remains.

Peatlands are globally significant carbon stores and important wetland ecosystems.

Peat forms in bogs, fens, mires and swamps where waterlogging starves the ground of oxygen and slows microbial decay. Dead plant material accumulates faster than it can rot, building up layer upon layer over thousands of years; peat typically grows only about a millimeter per year.

Widespread peatlands occur in cool, wet climates such as Ireland, Scotland, Scandinavia, Canada, Russia and Indonesia. With deep burial, compaction and heat over geological time, peat is transformed first into lignite and ultimately into higher-rank coals.

Peat is recognized by its dark brown color, light weight when dry, spongy texture, and abundant visible plant fibers. It is extremely soft, holds water like a sponge, and has a distinctive earthy, organic smell.

Unlike lignite it is loose, fibrous and uncompacted, and unlike ordinary soil it is overwhelmingly organic and burns once dried. It can be torn apart by hand and often reveals identifiable roots, moss and twigs. Its fibrous structure, low density and combustibility when dried are the simplest identifying tests.

Peat is widely used as a fuel, cut and dried into turf for burning in regions such as Ireland and Scotland. It is also a major horticultural product, valued in potting mixes and soil conditioners for its water retention and structure, though such use is increasingly restricted for environmental reasons.

Peat is used in whisky production to dry and flavor malted barley, imparting smoky notes. Scientifically, peat bogs preserve pollen, archaeological artifacts and bog bodies, making them valuable archives. Conserving peatlands is now a climate priority because they store vast amounts of carbon.