Wednesday, February 20, 2008

Hold back the flow ... of false claims on water for transportation

This past week my colleague Michael Webber presented some preliminary results (currently under review for publication at Environmental Science and Technology) at the 2008 annual meeting of the American Association for the Advancement of Science. A journalist from the Toronto Star reported about the results of our work. And Gordon Quaiattini, the president of the Canadian Renewable Fuels Association (CRFA), put in his 2 Canadian cents worth of comment to the Star editor.

First, our work on this is under review so I won't comment too much on the methodology until it is accepted and published, but I can clarify some aspects of the table in the Toronto Star article as well as the comment by Mr. Quaiattini.

As far as Mr. Quaiattini is concerned, let me assure him that neither me nor Michael are against biofuels. What we are for is understanding the impacts of all fuels. That is why we presented information that compares a variety of fuels, and future work can focus on additional biofuels and alternative fuels.

Mr. Quaiattini claims that 85% of U.S. corn is non-irrigated. This is fairly consistent value as in 1998 we show approximately 1.9 billion bushels irrigated (see Table 22) out of about 9.8 billion bushels of US corn grain (see and select 'US corn grain' stats for 1998 in the pull down menu) - this gives 15.6% irrigated. He also states the numbers of 3 gallons of water to process the corn into a gallon of ethanol, and this is at the lower end of the range of values we used.

The data presented in the aside in the Star article lists ethanol water 'use' (note in this case consumption and withdrawal are roughly equivalent) as 40-130 gallons per mile driven on E85. This is close, but not quite accurate as noted. We calculate 12-136 gallons per mile driven on E85 derived from irrigated corn in the U.S. The range exists because not all regions that grow corn need the same amount of irrigation. Obviously some regions get more rain than others. We have made no claim (yet!) on the total water consumed and withdrawn for travel in light duty vehicles in the US.

NOTE: when considering ethanol derived from non-irrigated corn, the values for consumption and withdrawal are less than 0.5 gallons/mile. This shows you that the vast majority of the water of concern is for irrigation.

Does this mean we should not use biofuels? ABSOLUTELY NOT!!!

What it does mean is that we need to understand the limits of our water resources while considering the tradeoffs that that the "biofuels vs. fossil fuels" debate entails. Fossil fuels are essentially really old biomass as nature has done a lot of work for us in growing the plants and storing them in the ground (over 100s of millions of years) for us to now use. Biofuels are essentially really young fossil fuels.

When planning for growing crops either for food or fuel, we need to use both the land and water resources responsibly. I applaud the efforts of the Canadian Renewable Fuels Association and other similar organizations that are helping promote alternatives to fossil fuels for transportation or stationary applications. I believe we can avoid a water conundrum, and our work is providing information to help society do just that.

1 comment:

Cassandra said...

The CRFA's Mythbuster's page is my favorite.

Interesting that they hire their own professional to do their studies rather than using peer reviewed work.