Can't drink ethanol

Posted May 1, 2007 in [Water]

Editorial: Can't drink ethanol

Sacramento Bee, April 29, 2007 - Businesses in California are racing to build plants to make ethanol, a substitute for gasoline that may or may not (depending on the study) lower greenhouse gas emissions. But it will take the state's most fought-over resource -- water -- to grow the crops used to produce ethanol.

Many crops can be used for that purpose, but at the moment ethanol plants are picking corn -- the most water-intensive ethanol crop there is. How much water? How much corn? The answer is startling.

The following, by admission, is a back-of-the-napkin look at ethanol's impact on California water. The numerical conclusions will undoubtedly be imprecise. But since we can't find any energy, water or utility agency that has given this topic a better look, the humble napkin is a way to start the conversation.

To illustrate the potential problem, let's make a couple of assumptions: California, which can't import enough corn because other states are producing more ethanol, has to grow all of this crop domestically. And let's assume the current trend continues, and corn remains the crop of choice to make ethanol.

So how much water does it take to grow corn? According to a study of California agriculture by the respected Water Education Foundation, it takes about 118 gallons of water to grow a pound of corn. And how many pounds of corn does it take to produce a gallon of ethanol? About 21 pounds of corn, according to one publication from the U.S. Department of Agriculture. So do the multiplication (118 gallons of water per pound of corn, times 21 pounds of corn) to get the water it takes to produce the corn for a gallon of ethanol.

If these numbers are accurate, the answer is about 2,500 gallons of water. For one gallon of ethanol.

Gulp.

There is a goal to produce about a billion gallons of ethanol in California a year. So each of those gallons of fuel, based on the calculations and assumptions above, would require 2,500 gallons of water. That's about 2.5 trillion gallons of water for 1 billion gallons of ethanol.

How much water is that in the scheme of things? Take all the water from the Sacramento-San Joaquin Delta that now goes to Southern California and Valley farms, use it to grow corn -- and it still wouldn't be enough water.

This back-of-the-napkin analysis suggests three things about ethanol in California. First, a water-intensive crop such as corn in the Central Valley is a bad choice. Second, since there is only so much water for agriculture in California, some other existing crops won't be grown. Third, it behooves the state to grow ethanol crops in the most water-efficient manner possible and set up laws and policies that guide industry in that direction.

It is downright scary to see such a rush to ethanol without a better look at the consequences.