The Entropy Index (EI) is rather easy to compute. We take the energy dissipated during any process, and multiply it by a scaling factor:
EI = dissipated energy * scaling factor
For example, driving a car with 20mpg efficiency for 20 miles burns 1 gallon of gasoline. We know that this produces a lot of heat (about 132000 kWh), which (simplifying slightly) is all dissipated in the atmosphere.
The scaling factor is the same for all substances and is set to 0.263, so that burning of 1 pound of coal (which produces 3.8 kilowatt-hours of energy) has the EI value of 100.