PEAT, a product of decayed vegetation found in the form of bogs in many parts of the world. The principal areas of the peat deposits of the world are as follows : Russia . ....... 65,00o square miles Canada ...... . 37,000 „ Finland ...... . 30,000 „ Sweden ...... . 19,000 „ „ United States 11,200 „ „ Germany ...... . . 9,900 Great Britain ..... . . 9,400 Ireland ...... . . • 4,700 ,, f t Newfoundland . . . . . . . 3,000 „ „ Norway ..... . . . 2,900 Austria ...... . . 1,500 Denmark 1, The plants which give origin to these deposits are mainly aquatic, including reeds, rushes, sedges and mosses. Sphagnum is present in most peats, but in Irish peat Thacomitrum lanuginosum pre dominates. It seems that the disintegration of the vegetable tissues is effected partly by moist atmospheric oxidation and partly by anaerobic bacteria, yeasts, moulds and fungi, in de pressions containing fairly still but not stagnant water, which iL retained by an impervious bed or underlying strata. As decom position proceeds the products become waterlogged and sink to the bottom of the pool ; in the course of time the deposits attain a considerable thickness, and the lower layers, under the superin cumbent pressure of the water and later deposits, are gradually compressed and carbonized. The most favourable conditions ap pear to be a moist atmosphere, and a mean annual temperature of about 45°. The peat bogs of Great Britain and Ireland vary in thickness from 5 to 3o ft.; and those of North America vary from 5 to 25 ft.
Peat varies from a pale yellow or brown fibrous substance, re sembling turf or compressed hay, and containing conspicuous plant remains, to a compact dark brown material, resembling black clay when wet and some varieties of lignite when dry. Two typical forms may be noticed : "Hill peat" (the mountain or brown bogs of Ireland), found in mountainous districts, and con sisting mainly of Sphagnum and Andromeda; and "Bottom peat" (the lowland or red bogs of Ireland), found in lakes, rivers and brooks, and containing Hypnum. The latter kind always contains much water, up to 90%, which it is necessary to remove before the product can be efficiently employed as a fuel, and for most other purposes. A specimen dried at oo° C had the following composition: carbon, 60.48% ; hydrogen, 6.10% ; oxygen, 32.55%; nitrogen, o.88% ; ash, 3.3o%; the ash is very variable—from 2 to 15% and even more—and consists principally of clay and sand, with lesser amounts of ferric oxide, lime, magnesia, etc. On air drying the peat loses from 8 to 20% of its moisture. In a good, dry season peat may be air-dried down to 17 or 18% moisture, while under moderate conditions it may be saved with 25 to 30% moisture. Average air-dried peat containing 25% moisture may be taken as having a calorific value of about 6,000 B.T.U. The specific gravity has been variously given, owing to the variable water content and air spaces; when dried and compressed, how ever, it is denser than water. The yield per sq.km. (0.386 sq.m.)
for a depth of five metres (16.4 ft.) has been determined in Germany as approximately 800,000 tons of air-dried peat.
Peat-winning presents certain special features. The general practice is to cut a trench about i f t. deep with a peculiarly shaped spade, termed in Ireland a "slane," and remove sods from 3 to 4 ft. long. When one layer has been removed, the next is attacked, and so on. If the deposit be more solid step-working may be adopted, and should water be reached recourse may be had to long-handled Blanes. The sods are allowed to drain, and then stacked for drying in the air, being occasionally turned so as to dry equally ; this process may require about six weeks.
Machine Working.—Mechanical power has been applied, especially in Sweden and Germany, to the winning of peat, the operations involved being :—( I) The excavation and elevation of the raw peat from the bog. (2) The maceration and mixing of the raw peat by means of rotating and fixed knives and a single or double screw conveyor which forces the peat through a nozzle or nozzles in a stream which is cut into lengths fcr sods. (3) The transport of the formed sods and their deposition on the bog. (4) The collection and stacking of the air-dried peat. In the most recent German practice the operations indicated in (I) (2) and (3) are combined in one machine electrically driven.
Several processes have been invented for the carbonization of peat and recovery of the by-products. Among these is the Ziegler process which is, or was, in operation at Oldenburg in Germany, Rodkino in Russia and Beuerberg in Bavaria. The uncondensed gases from the coking plant at Beuerberg gave:— The manufacture of producer gas from peat, in regard to which a number of methods exist, mostly based on the Mond process, has proved more or less successful. The briquetting of peat has also been carried out. The briquettes contain approximately 18% of moisture and are said to yield a high quality charcoal. One of the chief factors operating against the commercial success of peat as a fuel in competition with coal and other fuels has been the cost of drying the peat. With the recently introduced "Peco" process it is claimed however that the peat can be dried down to o% moisture and that 65% of the peat is recovered, that is to say in order to produce from I oo tons of raw peat 65 tons of dry peat, 35 tons of the raw peat are absorbed in drying. Perhaps Ireland is the largest producer with an output in the neighbour hood of 6,000,000 tons annually of air-dried peat.