The Big Biofuels Blog

Simon:
1. The title reads 12000 instead of 1200 (this is only for soils without precipitation..)

2. The byproducts of corn ethanol production(distiller's grains) get some CO2 credits in life cycle calculations. Did those performing the study (I did not read the ES&T paper) do similar calculations for water use?

That means it takes 3,172 gallons to grow one bushel of corn for food, plus another 8 gal or so to take it the next step to make ethanol. Sounds like a weak argument to me. Do you know how much water it akes to make the electricity you use in your house, or the gasoline you use in your car (assuming you have electricty in your house and drive a car of course)?

Thanks for pointing that out. I've corrected the headline.

Hi Ken, The argument gets a lot stronger if you live downstream from a corn producing belt and rely on a river for your drinking water.
It is also important if you are extracting that volume of water from an aquifer which is not being replenished at the same rate.
I don't have figures for the amount of water used in the other areas that you suggest. it would be interesting to look at the volume of water used per kW of energy produced from the different sectors. Do you have any numbers?

Depending upon the particular instillation, cooling water runs from 100 US gallons to 1000 US gallons per MWh generated.

Using the above values, one gets 360-3600 gal water/MJ of energy for electricity & 13.5 gal water/MJ of energy for ethanol, if my calculations are correct. [Ethanol HHV: 29.7 MJ/kg, density: 0.789 kg/L].

I believe around 4 percent of corn in the US is irrigated, and little if any of that is processed and used to best usages which involves making hundreds of products including ethanol out of it.

I believe most of the irrigated corn is used for people food.

more credible numbers are 8 gallons average per gallon of ethanol compared to 10 gallons average per gallon of gasoline.

The big difference is that every time we build a new ethanol distillery, the average water usage comes down. Current technology is 2 or 3 gallons of water per gallon of ethanol, thus each new distillery built is lowering the overall average.

Some are even claiming one gallon of water per gallon of ethanol.

(water recycled or fed to cattle as wet Distillers Dry Grains does not count against the ethanol produced nor does recycled cooling water and water pumped into oil wells to force the oil out count against the gasoline figures).

The ineffectiveness of biofuels—ethanol and biodiesil—has been much in the news lately, with reports from the EPA, California's CARB and the EU's joint Research Council claiming that biofuels pollute more than the fossil fuels they are supposed to replace. Still, this has not prevented the biofuels industry from receiving big government subsidies. Now a new report discloses another reason to shun biofuels, one that has nothing to do with CO2 and everything to do with H2O. When the water use of biofuel feedstock crops is analyzed, the water footprint (WF) ranges from 1,400 to an astounding 20,000 gallons of water for each gallon of biofuel produced. See my blog article for the rest: http://theresilientearth.com/?q=content/watering-down-biofuels