It's not that they don't put a lot of work into their work, they do, but some of it's fuzzy, some of it's poorly reasoned, and some of it's downright controversial.
A f'rinstance. They calculate the "oil equivalent" of the labor that goes into farming corn [and other ethanol-producing crops]. They figure up how many calories of food a farm laborer eats and how many gallons of gasoline a farm laborer uses to get from home to the fields and back, and then set this equivalent to X number of liters of oil and add this to the total energy put into producing the resulting ethanol [8000 liters/year/hectare here].
That's all fine and dandy, I like thorough analyses as well as the next number-cruncher [and maybe more], but they never once do any such figuration on producing an equivalent amount of gasoline. Oops. In fact, I've spent the last two years, ever since Slate lauded their anti-ethanol ethos here, trying to find out how much energy goes into producing the gasoline you use.
This is the best I've found so far [and it's not great, so remember your grain of salt]:
- It takes 0.74 BTU of fossil energy [coal + natural gas + petroleum] to
produceproduce and deliver to the gas pump 1 BTU of ethanol from corn.
- It takes 1.23 BTU of fossil energy [coal + natural gas + petroleum] to
produceproduce and deliver to the gas pump 1 BTU of gasoline from petroleum.
NB: As far as I can tell, nobody's found a link between Pimentel and Big Oil, but Patzek has ties.