BTU/lb (energy Content) are based on the weight of the fuel, now you have to combine that with the amount of fuel being used (Air Fuel Ratio) to get your total BTU (Total Thermal Energy)
Here is some simple Chart that I had, I'll do the math on E85 later but it winds up between gasoline and methanol.
lbs of air (lbs) A/F Ratio Pounds of Fuel (lbs) Energy Content of Fuel (BTU/lb) Total Thermal Energy (BTU)
Gasoline 42.64, 12.8:1, 2.89, 18,500, 53,176
Methanol 42.64, 6.0:1, 7.11, 9,500, 67,545
Nitromethane 42.64, 1.7:1, 25.08, 5,000, 125,412
As you can see the fuels with lower energy content put out more total BTU's sinces the overall volume is that much more due to the Air Fuel Ratio...