When you compare to the 'alternatives', it makes you aware of just how valuable oil, and by extension natural gas, really is.
WSJ: Ethanol's Water Shortage.
Ethanol plants consume roughly four gallons of water to produce each gallon of fuel, but that's only a fraction of ethanol's total water habit. Cornell ecology professor David Pimentel says that when you count the water needed to grow the corn, one gallon of ethanol requires a staggering 1,700 gallons of H2O. Backers of the Senate bill say that less-thirsty technologies are just around the corner, which is what we've been hearing for years.
Ethanol's big environmental footprint is not limited to water, because biofuels like ethanol are highly inefficient. In September, the Chairman of the OECD's Roundtable on Sustainable Development released a report entitled, "Biofuels: Is the Cure Worse than the Disease?" Authors Richard Doornbosch and Ronald Steenblik compared the power density of different energy sources, measured in energy production per unit of the earth's area. Oil -- because it requires only a narrow hole in the earth and is extracted as a highly concentrated form of energy -- is up to 1,000 times more efficient than solar energy, which requires large panels collecting a less-concentrated form of energy known as the midday sun.
But even solar power is roughly 10 times as efficient as biomass-derived fuels like ethanol. In other words, growing the corn to produce ethanol means clearing land and killing animals on a massive scale, or converting land from food production to fuel production.