how much energy goes into corn ethanol?

There have been a variety of conflicting studies over the past decade that probe the EROI (energy return on investment) of corn ethanol - basically you want to get more energy out than you put in...  The studies have shown conflicting results - some show EROIs less than 1.0 and some a bit over ..  

Here is an excerpt from a new paper that looks at regionality.

snip

The results from our meta-error analysis indicated that the average EROI for corn ethanol was 1.07 with a standard error of 0.1. The 95% confidence interval was 1.07 ± 0.2. This result is interpreted as follows: there is a 95% chance that the true value of the EROI of corn ethanol is contained within 0.2 of 1.07. Alternatively, this calculation means that we are unable to assert whether the true value of the EROI of corn ethanol is greater than one.

EROI values calculated in the spatial analysis ranged from 0.36 in less optimal corn-growing areas, for example southern Texas, to 1.18 in optimal areas, for example Nebraska (Fig. 2). If we apply the same confidence calculated in the meta-error analysis to the results of the county EROI analysis, we find that none of the counties had an EROI that was high enough (1.20) to conclude that corn ethanol was produced at an energy profit. The average EROI value across all counties was 1.01, which was 0.06 less than the average calculated across the literature. This supports the idea that the literature used optimal values for corn ethanol inputs and outputs and as such has underestimated costs, overestimated benefits, or both. The distribution of EROI values followed a normal distribution skewed slightly left (Fig. 3). The vast majority of counties had EROIs that fell within either the 1.01–1.05 or 1.06–1.10 category.

Our spatial analysis indicated diminishing returns to EROI as distance from the Corn Belt increased. Counties with high EROI values were located in Nebraska and other Corn Belt states, while the lower EROI values were located in counties toward the northwest or southeast of the area analyzed, essentially northwestern South and North Dakota, and southeastern Texas, respectively (Fig. 2). As expected, the counties with EROI values within the top 10% had a combination of higher yields and lower agricultural inputs, while the counties within the lowest 10% of EROIs had lower yields and higher agricultural inputs on average (Fig. 4). We can conclude that even with a precision of ±0.2, 48 counties have EROIs below 1, as the EROI calculated for each of these counties was <0.80 (Fig. 3).

No one has shown convincing data that suggests corn ethanol is a great, or even a good, thing.  At best it statistically consumes as much energy as it provides.  If you look at carbon flows, the situation may be even worse.

Of course there are powerful winners who are protected by the Federal mandate to use gasoline ethanol blends and a huge tax subsidy.  A sensible energy policy would remove the mandate and the subsidy - or at least the subsidy as that would make gas at the pump more expensive and might encourage a bit of conservation.   That would be politically impossible.

Comments

[Truman]

Please take a look at the following reports:
USDA - June, 2010: http://www.usda.gov/oce/reports/energy/2008Ethanol_June_final.pdf
University of IL-Chicago: http://tigger.uic.edu/htbin/cgiwrap/bin/newsbureau/cgi-bin/index.cgi?from=Releases&to=Release&id=2911&start=1267278161&end=1275054161&topic=0&dept=0

[sara]

many other studies have found corn ethanol not up to the task of making a dent in reducing carbon emissions. the usda study has been criticized as the product of an agriculture department under the bush administration with an agenda.

recently the congressional budget office skewered corn ethanol as an extremely inefficient way to lower carbon. a real boondoggle and waste of national treasure. of course agribusiness is huge and congress is afraid of them.

a bit more here http://www.grist.org/article/2010-07-16-ethanol-gets-skewered-by-recent-cbo-assessment.