UC Berkeley's Renewable and Appropriate Energy Lab, is pro-ethanol, and they do good work. They have reviewed about 10 of the best ethanol studies, corrected them, and produced the best compromise estimate. Their value for GHG reduction is even lower than the one used by zFacts. It would put the GHG savings at less than 0.1% in 2017 when corn ethanol has pretty much maxed out.

Berkeley put the GHG savings at 13% in their Science article, then corrected it to 8% Berkeley pdf

. Then the Academy of Sciences published a new study in July 2006 Academy pdf

, and came in at 12%. zFacts used the more optimistic 12%.

Using this value, the energy in ethanol, the amount of ethanol that USDA says can be produced in 2017, and DOE's total GHG emissions for the US, you will find a reduction of 0.13%. zFacts rounded that up to 2/10 of 1% to be generous in our headline. The bottom line for climate change and corn ethanol:

Maximum feasible corn ethanol production will have an undetectably small affect on GHGs, but will have serious negative environmental impacts.

Besides failing to help with GHGs and having serious environmental problems, corn ethanol subsidies are very expensive, and the political backlash in the next few years, as production and subsidies double, will damage the effort to curb global warming.

If you doubt this, check the ethanol-GHG calculation

Why it doesn't ethanol work better?
♦ Corn uses more nitrogen fertilizer than almost any crop.
♦ Making nitrogen fertilizer requires a lot of natural gas (fossil fuel).
♦ Tractors, trucks and harvesters take gasoline.
♦ Distilling ethanol takes a lot of heat--more fossil fuel.
♦ Nitrogen fertilizer and soil bacteria make N₂O.
♦ N₂O is a much worse green-house gas than CO₂.

While current ethanol production is probably saving 1.1% of imported energy, it plays a much less significant role in reducing total GHGs. First because a 12% reduction is much less than the roughly 90% effectiveness on imports of replacing a gallon of gasoline. Second because imported energy accounts for only about 1/4 of total GHGs. The result is that ethanol is just too small to matter in the GHG picture.

The negative impacts on GHG policy
The main effect of corn ethanol on GHG's is to divert $2.5 billion a year now, and very shortly $5 billion a year, of tax dollars away from significant GHG reduction efforts. The second effect is to construct 12 billion gallons per year of non-cellulose capacity that will compete with cellulose ethanol for the next 20 years and slow its introduction. The third effect is to let car companies off the hook. They get credit for building ethanol-ready cars that are never used for ethanol and that wouldn't help if they were.

http://zfacts.com/p/751.html | 01/18/12 07:17 GMT
Modified: Tue, 24 Apr 2007 00:36:13 GMT