Coalbed methane production which frees only the desorbed gas yields only from 0.2 to 2.5 percent of the total energy in the coal. However, the gases produced in UCG plants typically recover as much as 50-70 percent of the coal’s original energy value. The calorific values of UCG gas is from 100-350 btu/scf, which is 10-30 percent of that of natural gas.