Checking the Waste: A Study in Conservation

by Mary Huston Gregory

(1) A coal bed is not made up entirely of pure coal, especially if it be very thick. Sometimes there are layers of shale or clay, which makes a large amount of ash. This can never be sold as regular marketable coal; but it is rich in carbon, and much of it might be used if it could be marketed near the mines and sold as low-grade coal. In the past there has been almost no market for it, and if it were either in the roof or bottom of the coal bed, it has been left unmined. If mixed with pure coal, the low-grade coal was thrown into great heaps at the mouth of the mine. This refuse coal is called culm. The amount varies from one-tenth to one-half of the coal in nearly every coal bed, and would probably average one-fourth in all the mines of the country.

This material is rich in carbon, and when used in gas-engines will furnish more power than the best Pocahontas coal when steam-engines are used. Thus one-fourth of all our coal is wasted at the mines simply because steam-engines instead of gas-producer engines have been employed. If in the future installation of power this fact is taken into consideration, it will make the cost less to the user, and at the same time utilize a large proportion of our impure coal and save the higher grades for other purposes.

(2) In the mining of coal it was formerly the unfailing custom to leave supporting pillars of coal for the over-lying rocks to rest upon, to make suitable working-rooms, etc. These pillars, twelve to eighteen inches square, and higher than a man's head, are scattered throughout the entire mines and are usually of the highest grade coal. In many mines, also, a roof of coal a foot or more in thickness must be left because the material above the coal is not solid enough to prevent cave-ins. When the mine is abandoned and closed these pillars and roofings remain untouched, because removing them constitutes one of the greatest dangers to life, and is one of the frequent causes of mine accidents. It is improbable that the coal thus left in abandoned mines will ever be reclaimed, because not enough is left to make it profitable at present prices to re-open the mines; and frequently the rocks cave in about these pillars and make the task almost impossible.

(3) By careless blasting an unnecessarily large amount of coal is blown into powder,—the slack which has not been marketed at all until within the last few years. Much of this slack, which is the best grade of coal in a pulverized form, is left inside the mines. These wastes in abandoned roofing, pillars, and small-sized coal, together make a total which for all the mines in the country will average fully one-fourth more of the coal that is in the ground.

It is to be noted, however, that conditions are changing for the better. The most modern mines use fewer supporting pillars of coal, and these are of larger size, so that there is less danger of accidents. Wherever possible they use timbers of wood instead of these smaller pillars of coal. They also mine as near the top of the seam of coal as can be done safely, and so regulate the blasting that much less slack is made than by the heavy discharges. These changes in mining methods save a far larger proportion of coal, and also prevent many accidents, which are the most unfortunate feature of coal mining, and the one which should receive most careful consideration. (See chapter on Health.)

One large mining company in Kentucky raises its own timbers by planting trees in straight, close rows on its coal land, thus making the land produce its own mine timbers to conserve the coal below. This company claims to have lost but one life in ten years, and to save seventy-five per cent. of its coal. This is a striking illustration of what better mining methods will do for both the miner and the mine owner and of how forestry may be an aid to the conservation of coal and also of human life in the mines.

We have already shown how half of the coal is wasted, but there still remains another source of waste at the mines. This is a large but unknown quantity. Coal usually exists in beds or layers with shale or rock between, much as a "layer-cake" is made, the layers of cake being represented by the coal and the icing between by these "rock-partings," as they are called. In rich fields, there are from three to ten of these rich layers or beds of coal, one above another. It often happens that the thickest and best layer is the lowest, and when this is the case, it is usually mined first, regardless of the fact that some, and possibly all, of the higher beds are dislocated and broken or filled with deadly gases. Nearly all this loss could be avoided by simply mining the upper stratum first.

So much for waste at the mines. This is serious enough if it were all, but it is not all, it is only the beginning. Let us see now what becomes of the coal that is marketed. The railroads are the largest single users of coal, and here we are confronted with the surprising statement that our locomotives consume three tons of coal in doing the same work that is performed by English locomotives with one ton. This difference is said to be due to different construction of the engines themselves, and to more careful stoking, or firing. Our locomotives use 100,000,000 tons per year, and by even the best methods known a large proportion of the heat units is wasted. Great effort should be made to improve the locomotives so that they will consume less coal; but as long as the railroad companies own the coal mines, as they do in many instances, they can obtain coal so cheaply that the cost of the improved form of engine is greater than the amount saved.

Another great use lies in the manufacture of coke, which is used in the making of steel, and here, too, we see where great wastes have existed. The old form of coke-oven was called the bee-hive on account of its shape. These old style ovens consume all the coal with the exception of the fixed carbon which is left behind as coke. At the prices which prevailed in 1907, the value of the by-products wasted in bee-hive coke-ovens was a little over $55,000,000—surely a loss worth considering. A different form of coke-ovens is much used abroad and is coming into use in this country. This is the retort or by-product oven, sometimes called the recovery oven.

The bee-hive ovens are usually located near the mines where the cost of coal is low, with small expense for transporting it. On the other hand, the by-product ovens are established near the larger cities in order to dispose of their gas and other by-products. Here the cost of transportation must be added to that of the coal, but the products are marketed near by instead of at a distance, as in the case of the bee-hive ovens. The most improved by-product ovens produce not only coke and gas, but coal-tar, pitch, ammonia, and creosoting oils, all extremely valuable and adding greatly to the value of the output of the ovens.