Peat.
—As a fuel, peat has been used very little in the United States on account of the abundance of the better grades of fuel, but in many parts of the country it is used locally to a considerable extent. In peat bogs from which the fuel is taken, the peat is formed from grasses and sedges which in time produce a carbonaceous mass that becomes sufficiently dense to be taken out in sections, with a long narrow spade. The peat is then built into piles where after drying it is ready to be burned.
Wood.
—On account of its relative scarcity and correspondingly high price, wood is no longer a commercial fuel of any consequence. The low heating value of wood as compared with coal makes it a prohibitive fuel except in forest localities. Wood is commonly sold by the cord and no attention is given by dealers to its value in heat-producing capacity.
The desirability of wood as a fuel is chiefly that of reputation. It is usually considered that hickory is the ideal fire wood, dry maple a close second and that oak is next in desirability as fuel; following which are ash, elm, beech, etc., depending on the density of the wood. The price of wood per cord depends on the nearness and abundance of supply.
The actual heating values of different woods as determined by Gottlieb show that per pound of dry wood there is little difference in heat value between different kinds of hard woods, and that pine gives per pound the highest value of all. The table given below was taken from “Steam” published by the Babcock-Wilcox Co.
| Kinds of wood | Per cent. of ash | B.t.u. per pound |
| Oak | 0.37 | 8,316 |
| Ash | 0.57 | 8,480 |
| Elm | 0.50 | 8,510 |
| Beech | 0.57 | 8,591 |
| Birch | 0.29 | 8,586 |
| Fir | 0.28 | 9,063 |
| Pine | 0.37 | 9,153 |
| Poplar | 1.86 | 7,834 |
| Willow | 3.37 | 7,926 |
In considering this table it must be kept in mind that the values are for dry wood per pound.
As given in Kent’s “Engineer’s Pocket Book” the weights of different fuel woods per cord (thoroughly air-dried) are about as follows: