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Cellulosic Biofuel Process Close to Cost-Competitive

Switchgrass (Agricultural Research Service/USDA)

Switchgrass (Agricultural Research Service/USDA)

Chemical engineers at Purdue University in West Lafayette, Indiana have devised a process for producing biofuels from non-food feedstocks they say is nearly cost-competitive with fossil fuels. An economic analysis of the process developed in the lab of Purdue’s Rakesh Agrawal is described in the journal Biomass Conversion and Biorefinery (paid subscription required).

This method, called H2Bioil, creates biofuels from cellulosic (high cellulose) feedstocks such as agricultural residues like corn stover, or switchgrass or miscanthus, thus not impacting acreage devoted to food crops. This biomass is heated rapidly to about 500 degrees C in the presence of pressurized hydrogen. The gases that result are then passed over catalysts causing chemical reactions that separate oxygen from carbon molecules, and make the carbon molecules high in energy content, similar to gasoline molecules.

Agrawal says this process, for which a patent has been granted, is faster and produces greater quantities of biofuels than competing methods. The team’s initial implementation has generated biofuels in the lab and is being refined to become effective on a commercial scale. “Once the process is fully developed,” says Agrawal “due to the use of external hydrogen, the yield is expected to be two to three times that of the current competing technologies.”

The economic analysis in the journal shows that achieving cost-effectiveness for the process depends on the energy source used to create hydrogen. When hydrogen is processed using natural gas or coal, H2Bioil becomes cost-effective when crude oil is just over $100 per barrel. Hydrogen derived from energy sources that are currently more expensive — e.g., nuclear, wind, or solar — can drive up the break-even point. (Benchmark West Texas light crude is $84.08 per barrel, as of 5 June 2012).

Agricultural economist and co-author Wallace Tyner used a model that assumes corn stover, switchgrass, and miscanthus would be the primary feedstocks. “In the past,” says Tyner, “I have said that for biofuels to be competitive, crude prices would need to be at about $120 per barrel. This process looks like it could be competitive when crude is even a little cheaper than that.”

“If we had a carbon tax in the future,” Tyner adds, “the break-even prices would be competitive even for nuclear.”

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