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Max corn ethanol impact on total US GHGs = 0.13%
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This is the calculation of corn ethanol's maximum impact on GHGs.
Links below provide 2 or 3 page PDF excerpts from the original documents that show the values used highlighted in yellow, so you can conveniently check all inputs.
As described here, the key value (A = 12%) is more optimistic than the value reported by the pro-ethanol group at UC Berkeley . They report ethanol produces 87 to gasoline's 94 GHG units, for a savings of only 7.4%. This calculation uses entirely pro-ethanol or standard authoritative sources, and does not contradict any of them. It just completes a calculation that is long over due.
A = 12% is the reduction in GHG from replacing 1 gallon of gasoline with ethanol National Academy of Sciences
B = 1.23 is the # of GGEs of fossil fuel saved by not using a gallon (1 GGE) of gasoline (this includes the fuel used in production and transportation). Argonne National Laboratory
C = 8228 is the grams of CO2 saved by not burning a gallon of gasoline. Dept. of Energy (DOE)
D = 10,120 is grams of CO2 saved by not producing & using 1 gallon of gasoline. D = B x C
E = 1,214 is grams of CO2 saved by using 1 GGE ethanol instead of gasoline. E = A x D
F = 116,090 is BTUs of energy in 1 gallon of gasoline DOE, 2006
G = 76,000 is BTUs of energy in 1 gallon of gasoline DOE, 2005
H = 1.53 is gallons of ethanol needed to replace energy in 1 gallon of gasoline. H = F/G
J = 795 is grams of CO2 saved by using 1 gallon of ethanol. J = E / H
K = 4.885 billion of gallons of ethanol were produced in 2006 RFA.
L = 3,860 billion grams of CO2 saved from 2017 ethanol production. L = K x J
M = 7,122 trillion grams of CO2e GHG emission in the US in 2004 (most recent value) DOE
N = 0.054% percent of GHGs saved by 2006 ethanol production. N = L / M
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Maximum corn-ethanol savings in 2017
The USDA predicts that corn-ethanol production will reach 12 billion gallons per year by 2017, but by then it will be growing at less than 2% per year. This will save 12/4.885 times as much GHG, or 0.13% of the total US emissions.
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http://zfacts.com/p/729.html | 01/18/12 07:22 GMT
Modified: Sun, 13 May 2007 17:43:56 GMT
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