Monday, July 18, 2005

Biodiesel: Not the answer, either?

A new study from Cornell and California-Berkeley says that it takes more fossil fuel to make ethanol than the ethanol itself will yield.

Supporters of ethanol as a renewable energy source have claimed in the past that only 60% of the yielded energy is needed to produce ethanol, but the new study challenges that number.

"The researchers included such factors as the energy used in producing the crop, costs that were not used in other studies that supported ethanol production, said Pimentel" [one of the study's authors].
Not wasting any time, the Canadian Renewable Fuels Association issued a press release refuting the results, stating:
"Over the past decade, only two studies, both of which were conducted by Cornell University entomologist David Pimentel, have found the net energy balance of ethanol to be negative. The overwhelming majority of scientists... have argued Pimentel's studies use outdated data and a flawed methodology."

One thing that had not occurred to me before was this: How much fossil fuel energy is expended to produce petroleum fuels? Is it a productive formula?

1 comment:

  1. Well rats. It sounds like we've got a couple completely opposite conclusions about how much you get out vs. how much you have to put in.

    Here's the UNH paper that talks about biodiesel from algae: (New Hampshire sports cheer: Gimme a "U"! Gimme an "N"! Gimme an "H"! What's that spell? UNHHHHH!).

    It includes a great comparison of biodiesel against hydrogen. And here's what it says about the energy efficiency of biodiesel from a soybean crop, based on a report by DOE and USDA (

    ... biodiesel produced from soy has an energy balance of 3.2:1. That means that for each unit of energy put into growing the soybeans and turning the soy oil into biodiesel, we get back 3.2 units of energy in the form of biodiesel. That works out to an energy efficiency of 320% (when only looking at fossil energy input - input from the sun, for example, is not included). The reason for the energy efficiency being greater than 100% is that the growing soybeans turn energy from the sun into chemical energy (oil).

    That seems to be in direct contradiction to the 73% efficiency stated in the Yahoo article.

    But supposedly algae is much more efficient than soybeans, maybe 2-3 times better or more. Plus, you can use waste streams from humans and farm animals to feed the algae, reducing pollution. Plus, the algae can be used to produce fertilizer after its oil is extracted. And you can grow enough replace our *entire* current use of petroleum fuel for transportation on 9.5 million acres, about 1% of what we currently use for crops and grazing animals. And with zero net greenhouse gas emissions.

    Where do I go to invest in an algae farm?