Another kernel of truth

Posted April 29th, 2008 by Sylvia S Tognetti and filed in Ignorance of Ignorance

Last night Stephen Colbert explained the “efficiency” of corn ethanol, which has presumably “solved” the climate crisis – or at least provided a good introduction. You can fly across the Atlantic and wipe out an amount of land equivalent to 30 soccer fields! What he didn’t say is that conversion of land to soccer fields also emits carbon stored in vegetation and soil. And that it isn’t just the Brits raining on the petro parade. Last week I attended the AMS seminar on Biofuels, Land Conversion and Climate Change, in which several of our own American scientists – Joseph Fargione, Timothy Searchinger, David Tilman, and Daniel Kammen, provided a good overview of this topic (powerpoints here; podcast and vidcasts expected to be up shortly). A few highlights from my notes:

Previous research findings that corn ethanol reduces emissions by 13% did not consider land use change.

Use of land to grow corn for ethanol raises crop prices, not only for corn. So it is creating pressure to take land out of the Conservation Reserve Program – the amount of acreage in the program was reduced by 2.3 million acres in 2007, and >4.5 million are set to expire in 2010, but they could leave sooner if the farm lobby is successful in getting penalties waived for breaking their contracts.

It also creates pressure to convert native prairie grass to corn fields – native prairie grass fields store 286 tons per hectare of carbon, which is 160 more tons/ha than cornfields. From 2002-2007, >500,000 acres were converted in Montana and the Dakotas. The amount of carbon released is 93 times the amount “saved” by using ethanol.

But most new corn crops come from the displacement of soybean crops. This raises the price of soybeans, which leads to deforestation in the Amazon rather than here. The Amazon stores even more carbon than prairies (927 tons/ha), which is 815 tons/ha more than a soybean field. The amount of carbon released is then 319 times the amount “saved” by using biodiesel from soy. The worst case scenarios is palm oil from peatlands….

Then there is the issue of forgone ongoing carbon sequestration services that soils and vegetation would have continued to provide, and the indirect effects, which can be even more significant (e.g., food prices, algal blooms, biodiversity loss, water consumption….), not to mention the land that will be needed to double food production to feed the expected population of 9 billion.

Land use change overall is estimated to account for 1/5th of global emissions of greenhouse gases but my guess is that that estimate has yet to include increased pressure on land from biofuels.

The good news is, that not all biofuels fuels are alike and we shouldn’t be lumping them into a single category. Obtained instead from waste biomass, from switchgrass, and from other perennial crops grown on degraded lands, use of biofuels can be efficient and even carbon negative, and can provide an economic incentive to restore those degraded lands. Prices and markets alone won’t bring about the needed transition. As Kammen said in the final presentation, “there is no peak dirty energy.”

Apparently Joe Romm was also there and blogged it here.

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