Toward a Sustainable Agriculture Module II, Section C, Ethanol Activity
How much corn would it take to supply most of our automobile fuel through ethanol? (key)
So, if the whole US fleet could switch over to cars that run on 85% ethanol tomorrow, about how much of the US corn crop would have to go towards ethanol production?
about 350% of the 2011 crop, assuming you would use the same amount of E-85 as we do petroleum gasoline. 85% : 9.7% = 8.8, so to ramp up from the current situation where 9.7 % of the transportation fuel comes from ethanol we multiply the 40% of the corn crop that supplied that 9.7% by 8.8. 40% x 8.8 = 352.
What percentage of the total gas energy currently used for transportation would the ethanol supply?
about 56%
Multiply the percentage of ethanol in E-85 (85%) by the energy content of ethanol relative to gasoline (0.66). 85% x 0.66 = 56%
Motor gasoline accounts for about 59% of the transportation energy used in the US. What percentage of the total transportation energy needs would this ethanol supply? about 34%
If we just dedicated 100% of the US corn harvest to ethanol production, how much of the current US transportation energy needs could it supply? Almost 10%.
40% of the corn harvest supplies 6.6% of the petroleum/ethanol energy, which is about 59% of the total transportation energy. So 100% of the corn crop could supply about 16.5% of the petroleum/ethanol energy. Multiply 16.5% by 0.59 to get the percentage of total transportation energy.
From 1973 to 1994 US consumption of petroleum for transportation increased by an average of about 1.2% per year. From 1995 to 2005 it increased by an average of 1.7% per year. (Data taken from the US Dept. of Energy Transportation Energy Data Book: Edition 25, Table 1.13 accessed at http://cta.ornl.gov/data/index.shtml April, 2007.) Do these trends tell us anything about the impact of corn ethanol on petroleum dependence? They suggest that corn ethanol production has a negligible impact on our dependence on foreign oil. Without policies requiring energy efficiency, petroleum use is increases faster in a strong economy than corn ethanol production can realistically keep up with. From 2004 to 2005, when ethanol production increased by nearly 15% according to the Renewable Fuels Association, use of petroleum for transportation increased by nearly 2.3%. During the same period European petroleum use per person went down. Since 2008 our petroleum use has decreased. The decrease is probably due to higher gas prices, economic recession, and new fuel efficiency standards, rather than to the contribution of ethanol.