Photo: USDA/Creative Commons

Cross-posted from EarthTechling with permission

By Pete Danko

Starch-based ethanol (think: corn) is largely discredited as a smart alternative to fossil fuels – at least that’s what some people think – so a lot of hope is being put into cellulosic ethanol. It has the advantage of using plant matter that we don’t eat.

The problem: So far cellulosic ethanol is proving to be economically challenging. Despite a lot of government support, it has failed miserably in living up to the production levels called for under a renewable fuel standard passed by Congress a few years ago.

Now a study out of Purdue University, focusing on the economics of a novel cellulosic ethanol production process, is suggesting the biofuel might not be a total lost cause. The study says that cellulosic ethanol could be competitive with regular ol’ gasoline. The kicker, however, is that it takes fossil fuels to pull that off, and also depends on high oil prices.

The story begins with the work by trio of Purdue chemical engineers — Rakesh Agrawal, Fabio Ribeiro and Nick Delgass — who have been trying to find a way to use catalytic hydrodeoxygenation to get more fuel out of less biomass.

What the researchers do is heat switchgrass or corn stover to around 500 degrees Celsius in the presence of hydrogen. This breaks the material down and creates gasses. Catalysts then react with the gasses to separate oxygen and carbon molecules, “making the carbon molecules high in energy content, similar to gasoline molecules,” the university explained.

The researchers have said the energy output using their brand of catalytic hydrodeoxygenation, which they’ve dubbed H2Bioil, can be two to three times what a conventional process will yield.

But would this be enough to get cellulosic ethanol over the cost hurdle? Wally Tyner, a professor of agricultural economics at Purdue, went to work on figuring out if H2Bioil would be competitive against petroleum-based fuels.

In the past, Tyner has maintained that in order for biofuels to be competitive, crude oil would have to be around $120 a barrel. H2Bioil, however, appears to do better. It takes the break-even point down near $100 – right around today’s price for oil. “We’re in the ballpark,” Tyner said.

There’s an ironic caveat to this type of green energy, however: That price competiveness only works if fossil fuels – natural gas or coal – are used to obtain the hydrogen that H2Bioil requires. Hydrogen derived from other sources, including nuclear, wind or solar, drives up the break-even point. You have to wonder if there’s any point to burning coal to make biofuel out of corn stalks or switchgrass.

Tyner did note that a carbon tax — a pipe dream for U.S. greens — would change the cost calculus, possibly bringing solar and wind into the picture down the road.

Meanwhile, the chemists still have some work to do. Their process works in the lab, but some tweaking will be necessary to take it to a larger stage.

“This economic analysis shows us that the process is viable on a commercial scale,” Agrawal said. “We can now go back to the lab and focus on refining and improving the process with confidence.”

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