What is peat?
Peat is the term for partially decomposed organic matter that has accumulated in a moist environment. This decay of organic material into peat, called the humification process, is brought about partly by micro-organisms. Peat forms in places where there is an abundance of water. The resulting lack of oxygen causes only a partial decomposition of the organic matter.

What does peat consists of?
The chemical composition of peat depends on the formation process, the quality of the bedding, groundwater flow, amount of precipitation, and even, to some degree, the impact of airborne particles. A swamp with fen vegetation obtains moisture from the ambient soil and thereby contains some of the same substances that are found naturally in the soils around it, just as in all vegetation. In sulphide-rich soil, there may be a higher content of sulphur, while in soils with a naturally higher content of metals, some of these can be detected in the peat. An ombrogenous (precipitation-fed) bog, on the other hand, often contains very low percentages of substances from the ambient land, and there are relatively few variations locally and regionally. The past few years’ emissions of substances caused by humans are to be found in the surface layer of the peatland, since there is usually little downward transport of water in a natural peat layer succession. There is often a layer of fen peat under the bog peat, while in the border zones, there is often a natural fen section, called the lag. Decomposition of the peat, i.e. the degree of humification, also plays a role and determines the peat’s chemical composition. Low-humified peat contains the most cellulose, while high-humified peat contains various humus substances. In investigating a peatland in preparation for exploitation, extensive specimen tests are made and other material is collected in an effort to avoid peatlands with overly high levels of, e.g., sulphur and metals. For a more comprehensive analysis of the chemical composition of peat, see SGU:s home pages on peat.

How fast does peat grow?
Peat began to form in Sweden more than 10,000 years ago, but the main bulk of our peat capacity was formed during the past 2,000 years, after the climate change at that time, which gave us a cooler and moister climate. The growth rate of peat in our bogs varies, but an average in vertical depth of 0.5 mm a year is often mentioned. On the lateral dimension, there are studies that indicate a natural spread of nearly 10 cm a year. However, this growth has been halted in many places through the digging of ditches in the lag sections, which obstructs the further spread of peat. The annual lateral growth alone is equivalent to as much as 15-20 terawatt hours.

Peat, coalbalanse and the greenhouseeffect
The question of whether burning peat as a fuel has contributed to the so-called greenhouse effect has long been a subject of discussion. Complex relationships between carbon-binding in peatlands and possible emissions of methane and carbon dioxide, as well as the impact of e.g. ditching, are being scrutinized around the world. There are different matters of opinion concerning classification and standardization of fuels for the purpose of taxation, Swedish reporting in accordance with the climate convention, and preservation interests. This will in all likelihood be settled by the European Union, since other countries than Sweden use peat for combustion and many others use it for other purposes, such as a cultivation substrate and a soil improvement agent. Peat for soil improvement and cultivation is sometimes oxidized as well.