Re: Latest study shows bio and ethanol to be a was
Based on quick analyses a few friends (scientists in various fields) have done of Pimentel's biodiesel (and ethanol) energy balance assessments, and comparing to previous assessments (such as the 1998 assessment done by the DOE/NREL which they found a positive energy balance of 3.2):
1. Pimentel used highly inflated numbers for energy inputs practically everywhere. A few examples:
2. The electricity used by the soy oil processing plant he claimed was ten times as much as the DOE used in their analysis - even though the DOE's electricity figures were already inflated to twice as much as what plants coming online at the time were using. So, Pimentel's electricity usage in processing is at least 20 times what's realistic for processing plants.
3. Pimentel included the energy to build the farm machinery as an energy requirement - but didn't properly account for the fact that the machinery lasts decades (he basically treated it almost as if you have to buy new tractors, combines, and everything else every year or two).
4. Pimentel included the food eaten by workers (on the farm and everywhere) as a fossil energy input - as if one unit of energy in the form of any food requires one unit of energy in the form of fossil fuels to produce. Not at all realistic.
5. He included way, way, way too much lime as being needed for treating soils, and with a very high energy input for producing the lime. For example (these numbers come from Mark Ambrose of the NCSU FOrestry Dept.), in North Carolina, where the soil is highly acidic (so you need more lime than normal), farmers growing soy typically put 2500 kg of lime on per hectare every 3-4 years (so 625-833 kg/hectare). In the mid-western US, where soils are less acidic, considerably less is used. Yet, Pimentel claimed that 4800 kg is needed PER YEAR - roughly an order of magnitude too much for most soy farmland in the US).
6. He used fertilizer application rates too high by 20-50%, and overstated the fossil energy input for fertilizer production by at least a factor of 2.
7. Used plant processing efficiencies from the mid-80s (for the ethanol analysis) - modern efficiencies are far, far greater.
And so on. Basically at every step of the process, he greatly overstates energy inputs (ranging from 10% to hundreds of percentage points), and then also claims substantially lower yields (basically using the lowest yields he could find, even though it meant going back decades).
That's why Pimentel has no credibility in the scientific community. Unfortunately, the media doesn't care about that. Talk of his analysis has been going on all over the place - it seems that this is the start of a campaign against biofuels.