Steve Firth wrote:

While it's true that you get about 30kJ/gram from ethanol as
opposed to 50kJ/gram from octane (don't have a figure for
petrol, but it will be close), the discrepancy isn't so great as
to make ethanol unattractive as a road fuel.


Yes, you're looking at the wrong figure. With ethanol you need to
consider the total energy input to produce the ethanol, not just the
calorific value of ethanol itself. There's the biomass itself, then the
energy input required to distill the ethanol. Compared to biodiesel
(which can be cold-pressed) there's a huge energy input.

Good point - but given the difference in cleanliness of the
output, ethanol still wins as a city fuel, no?

--
Grunff