The January 11, NIPCC posted “A Measureable Planetary Boundary for the Biosphere” by Steve W. Running. The article examines the world’s population in 2050 and the ability to feed the increased number of people at that time.
The author claims increased food production will be difficult and this is a good argument about the ethics of growing corn for the purpose of making ethanol for automotive use.
An additional item for consideration is the practicality of renewable energy sources that require large land areas to produce substantial amounts of energy. These sources include solar, wind, and other biofuels.
A rough estimate of annual energy production per acre for renewables is 0.7 billion Btu/acre-year for solar, 0.15 billion Btu/acre-year for wind, and 0.03 billion Btu/acre-year for corn. For the United States annual electricity production is equivalent to 14 quadrillion Btu and annual energy expended for transportation is 27 quadrillion Btu.
Assuming some type of practical electricity storage sytem is developed, land requirements to produce all annual electricity from solar are 20 million acres and 90 million acres for wind. Land requirements to produce all transportation fuels from ethanol from corn are 900 million acres or 1.4 million square miles.
Clearly ethanol from corn is impractical as a renewable energy source. These calculations don’t include the fact it requires more energy to make ethanol than is contained in the product.