

BOSTON, Ma. President Bush recently signed a mandate into law requiring that at least 36 billion gallons of biofuels be produced in the US by 2022. But here at the AAAS annual meeting, scientists are questioning the sustainability of farming our way out of using oil.

At the Soil Protection for Sustainable Well Being symposium, several questioners from the audience pressed Luca Montanarella of the Institute for Environment and Sustainability in Milan, on whether or not biofuels were a sustainable phenomenon. He demurred, but did note that soil is a finite resource, just like water and oil. That means we will run out of good soil unless we take steps to grow things more wisely.

As I listened to the exchange, a phrase popped into my head for what intensive energy crop farming really is: phytomining the soil. Plants are used to extract carbon from the environment. We then turn that plant biomass into a liquid hydrocarbon that mimics the fossil fuels our entire transportation infrastructure is built on.

But there's a limited amount of the materials plant need in the soil. When we use industrial farming techniques, useful though they have been, we deplete the ground we walk on because we're drawing energy out of it, over and over. To paraphrase what one scientist said to me last night, if we scale up biocrop production, the heart of American farm country will start to look like the dry, dusty center of Spain. We're not close to it yet, but there is a hard limit on how much energy we can pull out of our environments without destroying them. And I don't mean for the cute animals, I mean for the human beings.

The biomass debate raging across AAAS highlights the impossibility of finding a free energy lunch. There are not a ton of great alternatives to using biofuel of some sort, if we want to maintain our current infrastructure. As

Lord Ronald Oxburgh said in his talk on "Earth-to-Engine" science,

"There is a travel challenge" that has been sparked by "the insatiable human need to travel." If we want to keep traveling, and even the greenest among us do, we really will have to change the transportation infrastructure. A start: stop making cars dozens of times the size of a human being.

After all, Jer Faludi made a great point with the headline of a Worldchanging post last year, "Your Stuff: If It Isn't Grown, It Must Be Mined."

The symposium also focused on the launch of a new soil mapping initiative that aims to provide a high-resolution global map of soil, including attributes like PH, carbon storage, and a host of other datapoints. Eventually, such a map could be used to track soil depletion from agriculture, regardless of intended crop usage.

Self-referential note: As you probably have deduced, I finally arrived in Boston for AAAS after several plane delays, beleaguered and jet-lagged but excited. So, if you're around and want to catch up, drop me a line.

Image: flickr/kables