NATURAL GAS COAL GAS WATER GAS PRODUCER GAS Cubic feet of gas 1,000 1,000 1,000 1,000 Pounds of water evaporated 893 591 262 115Experiments in Pittsburg have shown that 1,000 cubic feet of natural gas equals 80 to 133 pounds of coal. The coal used in the comparison varied from 12,000 to 13,000 B. '1'. 1'. per pound.
The Western Society of Engineers has stated that one pound of good coal is equivalent in heating value to 7-1/2 cu. ft. of natural gas.
As in the case of petroleum, the economy of burning gaseous fuels depends upon the locality.
Artificial Fuels. The waste of charcoal, coal, sawdust, etc., is often pressed into cakes or briquettes, by means of some adhesive mixture, with compression. Wood tar, coal tar, and clay are used, according to convenience. These cakes are compact, can be stored in small space, and are used where good fuels are difficult to obtain.