Who cares about peak oil when you have corn cobs?

The nation's biggest ethanol firm says costs for corn-cob biofuel are coming down. But what happens to the soil?

Published November 19, 2009 11:56PM (EST)

The old joke about cellulosic ethanol -- biofuel made from lignocellulose, the tough, woody, hard-to-break-down structural elements of plants -- is that it is always five years away from commercial deployment, and has been for the last 20 years, at least. The problem is not inherently technological: We know how to do it; the difficulty has always been in making the process cost-competitive with other fuels.

So the news that POET, the largest ethanol producer in the U.S., has managed to cut production costs for cellulosic ethanol from $4.13 a gallon to $2.35 a gallon in the past year at its trial plant in Scotland, South Dakota, is potentially significant. POET is now predicting big things, reports the Argus Leader:

"Two years ago, I would have told you this was a long shot," CEO Jeff Broin said. "Now I'll tell you that we will produce cellulosic ethanol commercially in two years."

Two years instead of five! That's a big improvement! According to Broin, the factors involved include "reducing energy use, enzyme costs, raw material requirements and capital expenses."

POET's preferred feedstock: left over corn cobs and other post-harvest remnants known as "corn stover" that farmers typically leave to rot on their fields. A few weeks ago, POET organized a "Project Liberty Field Day" in Emmetsburg, Ohio in which 16 different agricultural machinery companies demonstrated new equipment specifically designed for the collection of corn cobs.

I asked Robert Rapier, who has established himself as one of the more influential commentators on all-things-biofuels, what he thought of the news. The critical factor, he said, is knowing what the cost of the inputs are. How much will POET be paying for the corncobs?

"The key to this is going to be how much they have to pay for the biomass. The cost that is quoted assumes a certain price for the biomass. I had a farmer tell me recently that he wouldn't bother gathering it for the price POET wants to pay. So I would say that the costs mentioned in the news story are a best case scenario for getting the farmers to sell corn cobs at the right price."

But the question I always have when hearing about biofuels made from farm "waste" is what happens to soil fertility when you keep extracting more and more plant material from the life-cycle of the farm, and turn it into fuel? Not surprisingly, this is a hot topic among agricultural research scientists in Iowa.

From "Studying Stover Harvest Effects on Yield, Soil, Climate:"

Corn stover has been used for many years as bedding and food for livestock, as well as to nourish and protect soils. In recent years, the ubiquitous stalk, leaf and cob residue of corn plants left in fields after harvest has found a new market: as a potential source for cellulosic ethanol production.

But harvesting the stover -- which, when left in place, halts erosion and supplies vital nutrients back to the soil -- could have unintended consequences, from lowering the fertility of fields to affecting productivity, soil and water quality and even climate. A comprehensive new study by Iowa State University agronomy researchers may soon shed light on these questions.

One result of the study, according to the authors, will be better information on "the optimal nitrogen, phosphorus and potassium fertilization rates needed to supplement nutrients lost from residue removal."

That's not such great news. The production of synthetic fertilizer is highly energy-intensive and consumes a lot of fossil fuels. What's the good of replacing gasoline with cellulosic ethanol made from farm waste, if we need to burn more oil to replace the soil nutrients that we are subtracting from the earth?

By Andrew Leonard

Andrew Leonard is a staff writer at Salon. On Twitter, @koxinga21.

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