Peat or turf is an organic sediment formed in bogs or moors. It is formed from the accumulation of plant substance that is not or only partially decayed and represents the first stage of the coalification.
The term peat is used if the content of organic matter in a soil exceeds 30 percent. If the proportion is smaller, it is called moist humus or (obsolete) muck. Depending on the degree of compaction, a different heating value is obtained. The spectrum ranges from white peat over brown peat to black peat. Bright white peat makes the structure of the plants still clearly visible. Upon further decomposition, a homogeneous body is formed that seems to have no structure with the naked eye, which is called brown peat or colorful peat. The oldest layer of peat is black peat. The lower layers of a peat bog are more advanced in decomposition than the upper ones.
The formation of peat develops very slowly. The average value for peat deposits in a bog or moor is to be set at a mean value of one millimeter per year. Traditionally, peat was mainly used as heating material. Since ecologists now regard moors or bogs as biotopes that are worth conserving, extraction from intact moors no longer takes place in Germany. Predominantly, previously dried former bogs are used as peat deposits. Since the end of the 20th century, peat has been extracted by open pit mining in dewatered open pits. White peat is treated for commercial purposes after drainage. Black peat used to be manually cut and dried in the air. Today, peat is no longer machine-cut, but milled or excavated in a flow process and dried by open storage until further use.