PEAT.

By CHARLES A. DAVIS.

INTRODUCTION.

The peat deposits of the United States form one of the most important of the undeveloped resources of the country. Peaty swamps cover, in the aggregate, large areas in the region east of the Ninetyseventh meridian and north of Ohio River; they occur also along the Atlantic coast as far south as and including Florida. On the Pacific coast peat beds have been reported from southern California northward to the Canadian boundary. These potentially valuable swamp lands have for some years attracted the attention of those who have followed the progress which has been made in Europe in extending the use of peat for fuel and for various other purposes, but only in a limited degree and in a more or less speculative or often purely academic way.

The extent of the peat deposits of the United States is not yet well known. Very little systematic search for peat has been undertaken, but from what has been done it seems probable that a large percentage of the swamps and bogs which occur throughout the glaciated region of the country and on the poorly drained parts of the Atlantic Coastal Plain conta'n more or less peat of commercial value. A larger percentage of the swamps of the extreme northern part of the country along the Canadian border than of the Coastal Plain region will undoubtedly be found to contain peat of commercial value. In all cases, however, where peat is sought swamp land should be examined in attempting to locate deposits of this important raw material.

The most extensive use of peat in Europe has been for fuel. Most of the attempts which have been made to utilize peat deposits in the United States also have aimed at their development as sources of fuel. A chief reason for this has prabably been the fact that the best peat deposits in the United States lie almost entirely outside of the region of occurrence of known workable coal fields and in regions where the climate is so severe that there is need for large supplies of fuel for domestic use. In the same region there is also a constantly growing demand for cheap fuel for manufacturing.

The States in which the largest areas of swamp land are known are Minnesota, Wisconsin, Michigan, the northern parts of the States immediately south of them, New York, the New England States, Pennsylvania, New Jersey, and also parts of the States south, especially a narrow strip along the Atlantic border where the land is flat, poorly drained, and has a large annual rainfall. The fact that all

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these States, with the exception of northern Illinois, Indiana, Ohio, and Pennsylvania, receive their supplies of fuel from rather distant coal fields, largely by rail, has made fuel costly, especially in the last few years, and many attempts have been made to convert peat into fuel, both for domestic use and, to some extent, for manufacturing purposes. Up to the present time, however, practically none of these attempts at the production of a serviceable fuel from peat have been commercially successful.

It does not seem necessary in this place to go into the details of the causes of failure, but the whole matter may be summed up by stating that the lack of success has apparently not been caused by the peculiarities of the peat fuel itself, since in practically every case where the material has been offered for sale it has found a ready market and has been sold at prices which, while less than those paid for other fuels, were ample to have made the manufacturer of the material remunerative. Although failure has been the history of the production of peat for fuel in the United States, European countries in which peat is abundant have been increasing its production and use both for domestic fuel and for power until at the present time there are probably between 15,000,000 and 20,000,000 tons of peat produced and used annually for fuel in the countries of northern Europe. Because this steady increase in the use of peat for fuel and for other purposes goes on in European countries; because improvements are constantly being made there in methods of recovery and use which are adapted to utilization on a large scale; and because our peat deposits in the United States are not only neglected but also are often wastefully burned up to remove the peat from the surface of the ground, a brief review of the methods in use in northern Europe for the economical production and use of peat for fuel is given here.

EUROPEAN METHODS OF PRODUCING PEAT FOR FUEL.

The oldest and simplest method of preparing peat for fuel is that still extensively employed by the peasantry of Ireland and other countries of northern Europe. The peat deposit is drained as thoroughly as possible by open ditches, after which a special type of spade is used to cut the peat out from the beds in the form of bricks. The brick-shaped blocks thus formed are laid out on the surface of the bog and dried by exposure to sun and wind. Peat fuel made in this way is, however, very easily broken and very bulky, and the method is only adapted to very local production and consumption, and not to transportation. Peat fuel recovered in this way is called cut peat.

A second method by which a much more satisfactory product is obtained is coming into general use wherever peat fuel is made. The method is simple and, to a certain extent, resembles that just described, but differs from it in that the peat is reduced to a pulp by suitable machinery before being formed into bricks. The processes and the machinery for pulping and handling the raw peat have been greatly improved during the last 10 years until at the present time the necessary processes of digging, conveying, reducing to pulp, and

spreading the pulp on the drying grounds are all mechanical and are carried on by machines which work together and are all operated by a single portable and generally self-propelling engine.

The most serious difficulty which has operated against the production and use of peat as fuel is the fact that, as it lies in the bog, it contains about 90 per cent of water. Long experience has shown this water content can not be reduced below 80 per cent, even by most careful and thorough draining; consequently, in the production of air-dried peat, in which form it is actually used as fuel, and which contains from 10 to 25 per cent of moisture, from 8 to 10 tons, depending on the actual water content, of raw material must be handled to produce a single ton of salable fuel. Thus the charges for excavating, transporting, reducing to pulp, spreading, and drying the raw material must be all charged against the very small proportion of the dry product. Even if this charge is very small per ton, the fact that it must be multiplied by at least eight times makes it a formidable matter in estimating the cost of the final product, which, to be commercially profitable, must be sold at a low price.

The processes of production of peat for fuel, after the peat deposit is ready to work, when reduced to the lowest possible terms are: (1) Digging, (2) elevating and transporting to the macerating machinery, (3) pulping or maceration, (4) forming the pulp and spreading it in some way so that it may be quickly and thoroughly dried, (5) tending the material during the process of drying, and (6) gathering and storing. In five of these operations first named, from 8 to 10 times the weight of the salable material must be handled in the form of water, which is eliminated in the course of drying. Hence, the less this waste material is handled and the shorter the distances and the more directly it is transported the greater the chance of final profit when the fuel which is the result of all the operations is ready for the market.

These facts have led to a large amount of experimental work on the part of mechanical engineers and other practical and trained men both abroad and, to a somewhat less extent, in the United States and Canada.

Within the last three years there have been several very compact and powerful machines or, better, combinations of machines developed which are self-moving and operate directly on the surface of the bog. In this way the inventors claim to eliminate all needless transportation of the wet material with its high percentage and great weight of waste water. These machines combine digging, macerating, and spreading devices in such a way that until the wet, thoroughly pulped peat is spread in brick form on the surface of the bog or on other drying grounds to dry there is no break in the forward movement. The several types of automobile machines or plants in use have been developed independently, and although they present fundamental likenesses in their construction each of them attains in a practical and simple way the same end, namely, they dig, move, pulp, and take to the drying grounds large quantities of raw material with an outlay of power and manual labor small in comparison with what was formerly used to attain the same actual tonnage of final product. Peat fuel prepared as described is called machine peat.

PRESSING WATER FROM PEAT.

It has long been realized by those who have given the matter attention that it is very desirable to avoid the uncertainties inherent in the method of drying peat by spreading in the open air, because weather and climatic conditions limit production. The most certain solution of the problem seemed to be the invention of some form of mechanical device for ridding the peat of water. With this in view, there have been attempts made for more than 50 years to invent presses having capacity and power enough to remove the water from peat on a commercial scale by mechanical pressure. During this time about every form of press that could be devised has been given experimental or even commercial trial, but without any commercial success up to the present time.

The difficulties which have been encountered have been due in part to the peculiar capacity which the peat itself has for holding the water, which is a part of it as it lies in the bog. This water is held in at least three ways: First, mechanically mixed with the particles of vegetable matter which make up the solid matter of the peat. (This water is termed by some writers "free water.") Second, the water is held in the minute cavities in and between the cells and fibers of the vegetable structures which the processes of decay have not thoroughly broken down. This water is held in the peat by capillarity and is more difficult to remove by pressure than the free water. Third, a certain percentage of the water present in the peat is held in the vegetable matter itself, in the walls of the cells, fibers, and tissues. This water is probably chemically combined with the fundamental organic substances of which the vegetable matter is composed. Water in such combination can not be removed by pressure, at least not until the chemical substances, of which it is a part, are decomposed, but can only be dried from the substances with which it is combined. There is also a fourth way in which water may be combined, and doubtless is combined, in most kinds of peat: This is what may be termed colloidal water, and is apparently in chemical combination with the substances with which it is associated. This water in whatever percentage it may be present is seemingly never removed by pressure, but must be removed by destroying the chemical bonds by which it is combined with the organic matter. This destruction can be brought about by heat or by evaporation, but the assumed union is not destroyed by pressure alone.

During the year 1913 reports were received from Europe of the development of a press which, although it has not yet been thoroughly tested on a commercial scale, apparently has made a very considerable reduction of the water content of a number of kinds of peat on an experimental scale. The results reported were such as to warrant the further development of the press to determine its value when tried with many kinds of peat, and late in 1913 a small machine of commercial size was finished and tested under conditions similar to those found in commercial operations. It is claimed for this press that, although it has a large capacity, it will be very cheaply operated and will require but little power. It reduces the water content of the material which is pressed to below