Peat is the "forgotten fossil fuel." While oil, coal, and natural gas are exported around the world, few outside northern Europe are aware of this energy source.
In certain circumstances, peat can be an early stage in coal formation. Most of the time, however, peat is a unique material.
Peat forms in bogs. Bogs are a type of wetland with a high acid content. Like all wetlands, bogs are inhabited by marshy plants, including trees, grasses, and moss. The bog's acidity prevents this vegetation from fully decaying. This partly-decayed organic material builds up in bogs. Over millions of years, it becomes peat.
Peat is thick, muddy, and, when harvested, looks like dark, earthen bricks. Traditional peat harvesting involves a farmer or laborer manually cutting thick strips of peat with a large, sharp hoe. Areas of harvested peatlands are called cutaway bogs for this reason. (Today, industrial peat harvesting involves huge tractors that scrape peat from the surface of bogs. This scraped peat is then collected into bricks. This is called milled peat.)
Wet bricks of raw peat are pressed to force out water. The bricks are then dried further, using heat or pressure. The bricks are then used as fuel, mostly for heating homes and businesses.
Northern Europe, particularly Scandinavia and the British Isles, have the most peatlands harvested for fuel use. However, peat bogs can be found from Tierra del Fuego to Indonesia. Finland, Ireland, and Scotland are the biggest consumers of peat as a fuel.