As the case against corn-based ethanol firms up, we’re hearing a drumbeat of claims that corn is only a bridge to a bright cellulosic future. In this vision, ethanol won’t be distilled from corn grown on prime land but rather from stuff no one wants: plant “wastes,” wood pulp, prairie grass, pocket lint.

The latest such claim comes from Nobel Laureate Steven Chu, director of the Lawrence Berkeley National Laboratory at Cal-Berkeley. Flush with a $500 million grant from British Petroleum to develop biofuels from “alternative” sources, Chu recently declared that “We should look at corn as a transitional [ethanol] crop.” A press account of his talk paraphrased him as follows:

[W]ithin five to 10 years, Chu said, scientific discoveries and refining processes could improve enough to move grasses, woody substances, and waste to the head of the line for making fuels. Some grasses could provide five times the amount of fuel from an acre as corn.

Within five to ten years … here we go again. Cellulosic ethanol boosters have been sticking to that particular story for decades now.

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Meanwhile, while cellulosic boosters rack up points for consistency, we get yet another study predicting that the miracle fuel will remain a purely theoretical construct for the foreseeable future. (In a recent post, I summarized what’s becoming a quiet consensus among high-level policy makers: cellulosic is a bust.)

The new study, by Iowa-based business consultancy Context Network, says this (from a summary in, of all places, Biomass Magazine):

[T]he most significant finding was that cellulosic ethanol has little chance of becoming a major contributor to the biofuels market. “While there’s high hopes for cellulosic ethanol, it’s going to develop much more slowly than people think,” [the study’s lead author] said.

(Hat tip to Ron Steenblik.)

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Whoa. Now, it’s important to note that such bean-counter studies have a tendency to be wrong. According to my own economic models, my dog will start hassling me for supper at about 5:30 p.m. EST. But just a second ago, she flung a paw at me and started giving me what I call the “fish eye.” Reality is chaotic; it takes defying economists’ models to the level of a sport.

But it’s hard to argue with this logic:

The paper noted that there are only two cellulosic ethanol pilot plants currently operating in the United States. Other demonstration plants won’t begin producing until 2010 or 2011, making the short-term EISA requirement of having 100 million gallons of cellulosic ethanol by 2012 unattainable.

Meanwhile, as I noted in the post linked above, government officials with their ears to the ground in both the corn-farming and research communities — namely, a USDA researcher and the pro-ethanol chair of the House ag committee — have also expressed deep pessimism regarding cellulosic ethanol.

Given that cellulosic is widely hailed as the glorious endgame of what nearly everyone says is a pathetic fuel source — corn — it’s time to have a serious conversation about cellulosic ethanol and what its real prospects are.