Ethanol offers short-term solutions, but corn-based ethanol is not the answer
Ethanol may emit less CO2 and help reduce the demand for foreign oil in the short term, but ethanol and in particular, corn-based ethanol raises food prices, is less efficient than gasoline, diesel, and biodiesel, and is not a substitute for oil.
According to research compiled by National Geographic Magazine , the energy balance of corn ethanol, (the amount hydrocarbon fuel required to produce a unit of ethanol) is 1-to-1.3 whereas for sugar cane ethanol the ratio is 1-to-8. This suggests corn-based ethanol requires significantly more energy to produce than sugar cane ethanol. Corn ethanol is only marginally positive.
A major issue with corn ethanol is its impact on corn prices and subsequently, food prices in general. It is the price of oil that is impacting the price of corn because nearly all ethanol produced in the U.S. is derived from corn. Therefore, corn prices are inextricably linked to oil prices as well as to the supply and demand of corn as food and feedstock. Corn Prices while volatile and impacted from weather and other variables appear to follow the rising price of oil as illustrated in Figure 1. In turn, corn prices are also influencing other commodity prices where corn is used for feed for livestock.
The rising motor vehicle usage in China and India is escalating the already tenuous situation in the oil markets. With ethanol tied to oil prices we are beginning to see corn prices exacerbate the inflationary pressures at the retail level. Over the last year consumers are paying more for food with large increases in the prices of eggs, cereal poultry, pork, and beef which are tied to corn.
Figure 1 Corn Prices
Senate legislation for Renewable Fuels Standard calls for ethanol production to increase to 36 billion gallons by 2022 with 21 billion derived from as cellulosic material such as plant fiber and switchgrass . Corn is expected to comprise 42% of the ethanol production in 2002 from virtually all today. The fact is that ethanol production at its current level of 6 billion gallons equates to only 4% of our gasoline usage and is already impacting food prices. Gasoline consumption in 2005 amounted to 3.3 billion barrels or 140 billion gallons. Current estimates put gasoline consumption at 144 billion gallons a year in 2007. Even if vehicles could run entirely on ethanol, there is not enough corn harvest to substitute our demand for oil. We need a cohesive and coordinated effort using multiple technologies to develop alternative energies to reduce our dependence on foreign oil.
Performance
According to Renewable Fuels Association ETHANOL FACTS:
ENGINE PERFORMANCE, ethanol offers higher engine performance with octane rating of 113 in comparison to 87 for gasoline and has a long history in the racing circuit. In 2007, the Indy Racing League, sponsors of the Indianapolis 500 started using ethanol in racecars. However, the higher engine performance may come at a cost of lower fuel efficiency.
Table 1 Specific Energy, Energy Density & CO2
Efficiency
Gasoline offers 56% higher energy efficiency (specific energy) over ethanol as measured by kilo-joules per gram (kj/g). (As a reference: 1 kilowatt-hour = 3,600 kilojoules = 3,412 British Thermal Units) Biodiesel with 35 kj/g is 33% more energy efficient than ethanol at 24.7 kj/g.
In terms of energy density, ethanol would require larger storage capacity to meet the same energy output of gasoline diesel, and biodiesel. Ethanol requires a storage tank 48% larger than gasoline and 41% larger than diesel for the same energy output.
Please see Hydrogen Properties and Energy Units
For a quick review of Specific Energy and Energy Density – (Molecular Weight Calculator) the specific energy of a fuel relates the inherent energy of the fuel relative to its weight and is measured in kilo-joules per gram.
CO2 Emission
The molecular weight of CO2 is approximately 44 with two oxygen molecules with an approximately weight of 32 and one carbon atom with a weight of 12. During the combustion process, oxygen is taken from the atmosphere producing more CO2 then the actual weight of the fuel. In the combustion process a gallon of gasoline weighing a little over six pounds produces 22 pounds of CO2.
CO2 emission is a function of the carbon concentration in the fuel and the combustion process. During combustion ethanol produces approximately 13 pounds of CO2 per gallon. Gasoline and diesel produce approximately 22 and 20 pounds per gallon, respectively. CO2 emissions per gallon appear quite favorable for ethanol. However, the results are less dramatic when CO2 emissions are compared per unit of energy produced.
Figure 2 CO2 per KWH
When measured in pounds of CO2 per kilowatt-hours (KWH) of energy, the results show ethanol producing 6% less CO2 than diesel or biodiesel and 5% less than gasoline. In the case of ethanol, the lower specific energy of the fuel negates the benefit of its lower CO2 emissions. Meaning more ethanol is consumed to travel the same distance as gasoline or diesel thereby limiting the benefit of its lower CO2 emissions.
The bottom line is ethanol does not ameliorate our dependence on foreign oil and while it demonstrates higher performance for racecars, it is still less efficient than gasoline diesel, and biodiesel, and diverts food production away from providing for people and livestock. The reality is there are special interest groups that obfuscate the facts about ethanol for their own benefit. The real solution to our imminent energy crisis is alternative energies including cellulosic ethanol, solar, hydrogen fuel cells, and wind.