Peat is an organic sediment that occurs in bogs . When dried, peat is flammable. It is formed from the accumulation of not or only incompletely decomposed vegetable matter and represents the first stage of coalification .
The term peat for the fuel obtained from moors from rotted plant residues was adopted from Low German into High German in the 16th century and goes back to the Old Low German turf . Within the Germanic languages, the word is closely related to English turf and Dutch turf , which are both synonymous with German peat . It is also related to Russian дёрн djorn , German ' Rasen ' and its equivalents in the other Slavic languages .
Types of peat
From an organic matter content of 30 percent (remainder: water and minerals) the deposit is called peat; Contents below 30 percent are referred to as moist humus or (somewhat outdated) as peat earth. Fen peat that forms in fens is different from raised bog peat that is only produced in raised bogs . Some scientists also classify transition peat, the properties of which mediate between low and high bog peat.
Depending on the degree of compression, there is a different calorific value. The variation ranges from white peat to brown peat to black peat. The light white peat clearly shows the structure of the plants; further decomposition creates a homogeneous, at least unstructured body when viewed with the naked eye, called brown peat or colored peat. The oldest layer of peat is black peat. The lower layers of a peat store (because they are older, exposed to greater pressure and ventilated during the formation) are more advanced in decomposition than the upper layers .
Other terms used depending on the degree of decomposition are: turf, fibrous and pitch peat. Grass peat is the most recent formation and consists of little changed, still easily recognizable plant remains. He is tan and loose. Fiber peat consists of brown mass that has already become structureless and is interspersed with fibers of plant material that is difficult to decompose. Pechtorf is darker and more compact than fiber peat. It is the oldest, heaviest peat and shows hardly any traces of plants.
White peat is used as a fertilizer to loosen potting soil . The name is misleading because the content of fertilizing minerals does not offer a sufficiently broad composition for the balanced enrichment of deficient soils. The economic importance has changed considerably in favor of the ecological reassessment of wet bog areas.
Where the soil conditions permit the accumulation of standing, shallow water in shallow lakes and depressions in the floodplains, this will eutrophicate over time and silt up due to the dead plant remains .
The formation of peat is very slow. The mean value for peat deposits in a bog is an average of 1 mm per year (up to 10 mm = 1 cm per year is also known). The North German Teufelsmoor near Worpswede took about 8,000 years to form.
First, a nutrient-rich fen with peat is created. Under suitable conditions, the surface of the bog gradually decouples from the standing groundwater in the depression through deposits. The bog water now has a low pH value (around 3.4–3.7), hardly any nutrients and only little oxygen are dissolved, so that the aerobic and anaerobic decomposition of plant substances is inhibited. The raised bog plant communities, whose deposits form the raised bog peat, are adapted to this condition.
Plants that lead to peat and bog are found in large numbers and proliferate, but they especially develop matted roots. These include Gentiles ( heather , bell heather ) Sedges (particularly sedges types, and cotton grasses and cornices ), rushes , black alder , and especially peat moss ( Sphagnum ). Mountain pine ( Pinus mugo ) can also play a role in high-altitude regions . A distinction is made between fens , intermediate bogs and raised bogs , depending on the involvement of individual plants mentioned in the formation of the bog, the ecology and the hydrological conditions . In the former, sedge beds , reed beds and swamp forests dominate , in the low-nutrient intermediate and raised bogs, peat and brown moss are the main peat producers. Bogs are important natural carbon stores.
Up until the 18th century, the first cultivation measures in manual processing in large moor areas in Northern Germany were drainage via ditches and subsequent burning of the areas. Extensive peat fires caused smoke from the army until the 19th century .
Since the end of the 20th century, peat has been extracted using the open pit method in drained open pits. After the storage layers have been dehydrated, white peat is processed for retail use by milling and volume-reducing presses. Black peat used to be cut manually and dried in the air in hordes or squats. Today, peat is no longer cut by machine, but milled or dredged using a flow process and dried first by pressing and finally by open storage until it is used.
Traditionally, peat was mainly used as heating material. Since bogs are now viewed by ecologists as biotopes worth preserving , there is no longer any mining from intact bogs in Germany; former bogs that have already been drained in the past are primarily used as peat storage sites. In Scandinavia and Ireland, as well as in the Baltic States , peat is still locally mined for energy and heat generation and is mainly used for local supply.
The properties of fens and raised bogs differ considerably. Fens play no economic role (except for reclamation ), only small amounts of fens are extracted for balneological purposes. The use of peat as fuel on the North Sea coast has already been handed down by Pliny ; An Arab traveler of the 10th century also reports of “combustible earth”. Raised bog peat was of great importance as fuel in the form of inferior sap peat from the 15th century to the beginning of the 19th century and in times of need in the 20th century . Currently it is mainly used in the plant industry and in large quantities by both professional and amateur gardeners.
By breaking down the peat, which requires drainage in order to be able to drive on the areas and use machines, the affected bogs are largely destroyed as natural areas. In view of their slow growth and the difficult procedure involved in drainage, they can usually no longer recover. In many countries such as Germany , Canada and Finland , pitted areas are regenerated by rewetting. After the mining licenses have expired, the regional administrations operate projects for rewetting, regeneration or for the agricultural and forestry use of former peat mining areas. Due to the growing ecological awareness of the population, simply leaving pitted areas lying around is no longer an accepted practice. In addition, the drainage of adjacent areas usually requires controlled water flow. The approval of new areas for dismantling is subject to strict conditions.
As a fuel, peat has a calorific value of 20–22 MJ / kg when dry , comparable to lignite . However, fresh peat has a very high water content and therefore usually has to be laboriously dried before being burned. In addition, peat has a very high ash content, low ash melting point and contains some chemical components that behave corrosive during combustion and / or the environment. The burn takes place very slowly, the ash contains a lot of unburned matter and therefore glows for a long time. For these reasons, peat is one of the more problematic and inferior fuels. Open peat fires have a very strong smell because of the acidic components they contain.
Essential peat as fuel is still in the malt production for many Scottish whiskey varieties, as the peat smoke contributes significantly to the flavor of the final product; Whiskeys produced outside of Scotland tend not to use peat smoke. As a fuel for general use, peat is only used in significant quantities in regions with extensive moorland. In Europe these are mainly Scandinavia (Finland, Sweden), the British Isles (Ireland, Scotland) and the Baltic States (Estonia, Latvia, Lithuania):
country Energy generation
from peat [ ktoe / a ] 1
(as of 2010)
Share of peat in
fuel consumption [%]
(as of 2010)
Finland 2280 7th Ireland 5 Sweden 0.6 Estonia 1.2 Lithuania 0.3 Latvia 0.1
- Source: Paappanen & Leinonen (2010)
The use of peat in these countries is very different. In Finland, Ireland and Sweden the majority is burned in larger power and heating plants, in the Baltic states in small heating systems.
- Peat power plants
Some bog-rich countries operate peat power plants that use peat on a large scale as a fuel to generate electricity. In the past, the peat was mainly burned in sod / ball form on a grate , now it is mainly used in ground form in a fluidized bed .
- Peat pellets
- Peat coal
Instead of using it directly as fuel, peat can - similar to the production of charcoal - be slowly converted into peat charcoal in a coal pile with little air or oxygen supply . In this way, a fuel is created that has a significantly higher calorific value and more favorable combustion properties.
This process was widespread in the 18th and early 19th centuries, as the need for high-calorific fuels increased rapidly with industrialization in ore smelting , in brickworks and other industries. Since "real" coal was not yet available in sufficient quantities and charcoal had become scarce due to large-scale deforestation, it came about that due to the increasing settlement pressure, large peat areas were reclaimed and therefore peat in larger quantities was used as a cheap fuel for charring Was available. This made peat an important supraregional trade good. Since peat ash continues to glow for a long time, this led to many fires . From the middle of the 19th century, with the invention of the railway and after afforestation with fast-growing conifers, the lack of coal and wood subsided and peat coal became less important.
- Whiskey production
In some whiskey -Destillerien, especially on the Scottish islands, which is malt over a peat fire kiln-dried . Originally this was a simple imperative, as Scotland is very poorly forested and wood or charcoal fires were therefore too expensive. The peat fire has meanwhile become an important flavor carrier; just as the special rauchig- can phenolics taste of some whiskeys are achieved.
- Fuel for steam locomotives
Peat was also used as heating material for steam locomotives in various areas . Because of the (already mentioned) long afterglow of the peat ash , these locomotives (the Oldenburg G 1 for example) had characteristic pear-shaped chimneys to prevent forest fires . In order to be able to carry a corresponding amount of peat, steam locomotives sometimes led several closed peat tenders or so-called peat ammunition wagons behind them.
- Heating material for gardening businesses
Large quantities of peat were burned in the region, also to provide horticultural businesses with heat for greenhouses. A large company in Wiesmoor , the Wiesmoor nursery was opened in the 20th century in the vicinity of a peat power station. The regions of Ammerland and Ostfriesland are known for their great variety of azaleas. The origins of greenhouse crops in the Netherlands and Flanders can be traced back to the use of peat as heating material and substrate.
Since peat can store many times its own weight in water, it is neutralized with lime, mixed with nutrient salts and other additives such as clay or sand, and thus processed into a growing medium. Some plants such as azaleas need acidic soil and so the addition of peat usually also serves to precisely regulate the acid balance of the soil. In professional gardening, there are hardly any alternatives for peat. The use of peat in private gardens is particularly criticized by nature conservationists . Every year hobby gardeners spread around 2.3 million cubic meters of peat to improve the soil. Without prior neutralization and fertilization, this can only improve the aeration of the soil, otherwise it can deteriorate the soil quality, as raised bog peat is extremely poor in nutrients and leads to soil acidification .
Peat substitutes are now made from bark or wood waste, which have a similar soil-improving effect, but hardly contribute to the acidification of the soil. In many cases, simple compost is the best way to improve soil.
Peat is also used in medicine and personal hygiene , especially as a mud bath , mud packs and even as a peat sauna. Bath peat differs from normal peat in its low number of harmful microorganisms. The healing properties of peat have not yet been fully researched. Balneologists suspect a healing effect if the peat is applied to the skin as a viscous mud paste at temperatures of 38 ° C to 40 ° C. In particular, the associated heat treatment, as well as the contained humic acids , promise a positive influence on the endocrine system and promote blood circulation in the body. The mild humic acids, which are contained more in black peat than in white peat, have a particularly positive property. The humic acids cause better blood circulation in the skin and make it appear soft. The humic acids are in the weakly acidic range pH around 5.7. The peat for external applications is obtained from unused agricultural areas. The most suitable mining areas for heavy black peat for the production of peat baths and packs are in East Frisia.
Textiles that are particularly light and warm can be made from peat fibers. Black peat can also be used to produce activated carbon . In the past, peat was also used as litter in stables. So was z. For example, the peat cut in Aukštumalė (known from the first monograph on a raised bog from 1902, today Lithuania ) was created to gain litter for the horses of the Königsberg horse-drawn railway .
In the last decades of the 19th and the first decades of the 20th century, the Haspelmoor peat litter and mulch plant mined large areas of peat. It served as stable litter and mainly as an insulating material for ice cellars and above-ground ice huts for breweries and restaurants. Haspelmoor peat was sold all over Europe.
In the past, peat was occasionally used as an inexpensive sleeping pad (peat bed) and was particularly suitable for bed- wetters and small children. Peat fibers have also recently been used again as a natural raw material for mattresses, duvets and pillows.
Another application can be found in the area of aquaristics and pond maintenance. Black peat is primarily used here as a filter material to reduce the pH value of the carbonate hardness. As solid black peat granulate, it can be filtered. The formation of algae and fungi is greatly reduced and the nitrogen content is lowered. The water becomes clearer. The peat causes the water to brown slightly (black water effect). Black peat contains fulvic acids, which protect the mucous membranes of the fish from bacterial infestation.
In chemistry, peat is also used as a natural ion exchanger.
Souvenirs are occasionally made from peat in active mining regions .
In the countries
There are around 271 million hectares of peat soil worldwide. Africa 6 million hectares, North America 135 million hectares, South America 6 million hectares, Asia 33 million hectares, Europe 88 million hectares, Middle East 2 million hectares and Oceania 1 million hectares.
Here, peat was and is being mined in the federal states of Rhineland-Palatinate , Lower Saxony , Schleswig-Holstein and Mecklenburg-Western Pomerania . The peat stocks increase from west to east. If the peat thickness in Lower Saxony (e.g. Wiesmoor ) is a maximum of two meters, the peat thicknesses in the river bogs are e.g. B. from Peene , Trebel and Tollense in Western Pomerania between nine and twelve meters. Because of the lack of fuel supply in the north of the GDR , peat was extracted mechanically in peat cooperatives until the mid-1950s and processed as a fuel in demand for heating purposes (dry peat or pressed peat). Only after the peatlands were left usually at rest, that is, it was made out of grazing and haymaking in parts of the areas little use since 1990 are in keeping with findings that Torfpolder rehabilitated and rewetted . Many of the river bogs are now under nature protection (e.g. Peene Valley ).
In the Bavarian foothills of the Alps there are also some areas where peat was extracted, such as the Ainringer Moos, the Kendlmühlfilzen near Grassau with a thickness of seven to eight meters, the Kollerfilze near Bad Feilnbach , the moors near Kolbermoor and the Weid- und the Schechenfilz near Iffeldorf . These areas represent all silting areas of former or still existing lakes (here: Chiemsee , Rosenheimer See , Starnberger See ).
Every year around 8.2 million cubic meters of peat are extracted from northern German moors from an area of 20,000 hectares (or eight percent of the raised moors). Today, peat is imported from the Baltic States and Russia to meet demand .
Peat (Engl. Peat ) was in England mined since Roman times. Interesting places can still be found today (for example the Somerset Levels ) where up to ten meters deep mining sites have unearthed archaeologically interesting finds (such as The Sweet Track ).
In Finland , peat is used extensively as about a third of the country is made up of peat soil. About 800,000 hectares are industrially usable, but the average depth of the peat is only about 1.4 m. About 8 percent of the electricity and 6 percent of the total energy requirement in 2003 were generated from peat. There are around 40 power plants that burn peat and wood, and 10 percent of the population heats with peat, which is usually supplied as pellets . The largest companies are Vapo Oy Energia in the city of Jyväskylä and Turveruukki Oy in the city of Oulu .
In 2001, 6 million tons of peat were produced for energy production and 0.5 million tons of peat for agricultural use.
Peat covers about one sixth of the land area in Ireland. The majority of the peat found here did not arise in depressions, but covered as a blanket bog , a subspecies of the raised bogs , more or less evenly wide stretches of land. This initially seemingly unnatural deposit was created on the one hand by the high rainfall in Ireland, on the other hand it was also intensified by human influence. In particular, the almost complete clearing of forests a few thousand years ago led to the formation of the first layers of peat. The top layer of plants initially served as grazing land. The natural evaporation was thereby greatly reduced. To avoid being washed away by soil erosion , people dammed the water with walls made of field stones. Over the millennia, this also led to the growth of peat as a blanket that enveloped the landscape. In the 21st century there are about one million hectares of such overhead bogs, which are on average 3 m thick.
In Ireland there are only around 200,000 hectares of bogs formed in depressions. Since these are significantly older - they were formed shortly after the end of the Vistula Ice Age 10,000 years ago - they are on average 7 m thick and are therefore primarily mined. The inhabitants had been mining peat for fuel since the 18th century, and there was no longer enough wood from the forests for a long time. These moors have all but disappeared in Ireland.
The peat production in 1999 was about 4.7 million tons.
In 1946, the semi-state owned company Bord na Móna was created by the Turf Development Act (TDA), which was intended to promote industrial peat use. The TDA operates a very large rail network of around 1200 miles, which is required for peat extraction, and issues mining licenses for a fee to private individuals for a limited time and area.
In Switzerland , the extraction of peat is de facto forbidden because peatlands of national importance have been under absolute protection since the adoption of the Rothenthurm Initiative in 1987 (Art. 78 (5 ) of the Federal Constitution ). No other country knows (as of 2010) a similarly high level of protection for bogs. However, around 150,000 tons of peat are imported from abroad each year, which is mainly used in horticulture . Specifically, this is 171,000 cubic meters (corresponds to 32% of peat imports ), the equivalent of more than 2,200 shipping containers , with which goods are shipped to Switzerland across the Rhine, for example. Since a large proportion of consumption is private, it is important to rely on peat-free soil in your own garden. To reduce the use of peat, the Federal Council is primarily focusing on the implementation of voluntary measures.
Natural peat fires
Natural peat fires are earth fires that can be externally ignited or self- ignited . In principle, peat catches fire where the groundwater is artificially lowered, no rain falls and slash and burn is carried out or where a forest fire is raging. High air temperatures, low humidity and wind (it promotes the drying out of the surface - even in shaded areas) promote inflammation.
In Africa, for example, there are areas in which large amounts of water are diverted into arid areas during the rainy season and a swamp area is created there for a few months a year, which leads to the formation of peat. This is the case in Mali and Botswana . When the water then evaporates and the peat dries from above, normal temperatures of approx. 40 ° C are sufficient to set the top layer of peat on fire by spontaneous combustion. The process is the same as with self-igniting coal fire or with haystack self- ignition .
In 2010 there were several giant peat fires in Russia. See 2010 Russian forest and peat fires .
At the beginning of September 2018 there was a moor fire in the Emsland district near Meppen after rocket tests, two weeks later eight square kilometers were already affected. See Moorbrand in the Meppener Heide 2018 .
In Indonesia there are large peat forests that grow on peat beds several meters deep. After one million hectares of marshland had been drained as part of the Mega Rice project on the island of Borneo , forest and peat fires started there, causing at least 40 cm of peat to be lost on an area of 500,000 hectares.
In 1997, about ten million hectares burned, shrouding Indonesia and parts of Southeast Asia in dark smoke for ten months. Enormous amounts of the greenhouse gas carbon dioxide were released into the atmosphere. A significant part of the Indonesian forests grow on mighty peat beds in which large amounts of carbon are stored. These areas in particular had caught fire at the time. The giant fires in these peat forests increase the global greenhouse effect measurably. Satellite image evaluations by the Ludwig Maximilians University in Munich showed that peat fires in Indonesia alone released a gigantic amount of 0.8 to 2.5 gigatons of carbon dioxide. This contribution - from a comparatively very small area by global standards - corresponds to between thirteen and forty percent of the global carbon dioxide emissions from the combustion of oil, coal and gas in the same year. In 2015, emissions from peat fires in Indonesia reached their highest level since the 1997 disaster, and exceeded emissions from the entire US economy for the month of September.
In Mali, in the floodplain of the Niger River , underground peat beds have been discovered which, especially in the dry season, keep catching fire and destroy all organic matter, including tree roots. Temperatures of up to 765 ° C occur on the surface. Since 1960 some scientists have suspected a volcano in the area, but in 2001 this assumption was refuted and peat fires were named as the cause.
The Okavango is an approximately 1,700 km long river in southern Africa that seeps into the swamps of the 15,000 km² (above-ground) drainless and swampy Okavango Basin in Botswana in the northeast of the Kalahari desert . During the rainy season it floods the basin on average a little more than a meter high.
Due to the large amounts of evaporated water, salt accumulates on the highest land elevations that are flooded during the rainy season , which leads to massive plant deaths. The sand carried along by the river collects in these places and can lead to the formation of an island. This means that there are fewer and fewer floods, until finally the island remains dry all year round, which in turn leads to the peat that has formed underground drying out; the prerequisite for a self-igniting peat fire is given. The fire destroys the island and flushes the salt and sand into the resulting underground cavity. This means that the cycle, which lasts around 150 years, can begin again. This natural process prevents the formation of a hostile salt lake or salt clay plain , which is actually to be expected with the high level of evaporation .
Peat is referred to as an organic soil horizon with the horizon symbol H, where nH stands for low peat, uH for transitional peat and hH for raised bog peat. In Austria and Switzerland, layers of peat are also identified with the letter T. 30% by weight of the soil should consist of humified organic matter.
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