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July 13, 2006
New Biofuels Study - Positive EROEI But Bad For Food Supply
In this never ending debate, there is yet another study suggesting that corn grain ethanol and soybean biodiesel have positive energy return on energy invested (EROEI).J. Hill, E. Nelson, D. Tilman, S. Polasky and D. Tiffany. "Environmental, economic and energetic costs and benefits of biodiesel and ethanol biofuels", PNAS, 103 (30) 11206, 2006
An interesting bit (highlighted part contributed by me):
In short, we find no support for the assertion that either biofuel requires more energy to make than it yields. However, the net energy balance (NEB) for corn grain ethanol is small, providing ~25% more energy than required for its production. Almost all of this NEB is attributable to the energy credit for its DDGS coproduct, which is animal feed, rather than to the ethanol itself containing more energy than used in its production. Corn grain ethanol has a low NEB because of the high energy input required to produce corn and to convert it into ethanol. In contrast, soybean biodiesel provides ~93% more energy than is required in its production.Concerning these energy credits that are given to ethanol because the by-products can be used as animal feed: Referring back to the podcast where I spoke to Tad Patzek, he brought up the interesting points that:
- This feed can often make animals sick
- It would be much better to return by-products back to the soil to minimize nutrient depletion
Biodiesel provides 93% more usable energy than the fossil energy needed for its production, reduces GHGs by 41% compared with diesel, reduces several major air pollutants, and has minimal impact on human and environmental health through N, P, and pesticide release. Corn grain ethanol provides smaller benefits through a 25% net energy gain and a 12% reduction in GHGs, and it has greater environmental and human health impacts because of increased release of five air pollutants and nitrate, nitrite, and pesticides.And the conclusion (which sounds like the way Shell is talking about biofuels these days):
Global demand for food is expected to double within the coming 50 years, and global demand for transportation fuels is expected to increase even more rapidly. There is a great need for renewable energy supplies that do not cause significant environmental harm and do not compete with food supply. Food-based biofuels can meet but a small portion of transportation energy needs. Energy conservation and biofuels that are not food-based are likely to be of far greater importance over the longer term. Biofuels such as synfuel hydrocarbons or cellulosic ethanol that can be produced on agriculturally marginal lands with minimal fertilizer, pesticide, and fossil energy inputs, or produced with agricultural residues, have potential to provide fuel supplies with greater environmental benefits than either petroleum or current foodbased biofuels.
Posted by dymaxion at July 13, 2006 06:58 PM