Switchgrass as Ideal Biofuel Feedstock?

Switchgrass as Ideal Biofuel Feedstock?:

The biofuel sector is aimed at weaning us off our dependence on oil, but what of biofuel producers' dependence on corn?

American bioethanol production is still vastly reliant on corn as a feedstock. In the short term, with total output volume still relatively low, corn remains a viable feedstock option. But as ethanol production continues to ramp up, corn prices will likely increase as biofuel producers compete with corn purchasers in the food and grain markets.

What alternatives do we have? A new research review published today in the journal GCB Bioenergy states that switchgrass is indeed viable as a cellulosic feedstock, as has been previously suggested, and that it may have advantages in carbon accumulation over other options.

"We reviewed over 100 articles on switchgrass, which found that this crop has a considerable ability to accumulate carbon in the soil compared to several other grasses, and especially row crops,” lead author Dr. Andrea Monti of the University of Bologna, Italy said in a release.

The review focused on research that measured the uptake of carbon dioxide, methane and nitrous oxide by switchgrass over the course of its lifecycle, including cultivation and processing. Estimates varied throughout the body of research Monti reviewed, which is due to variables ranging from how the switchgrass was cultivated and variations in biofuel production processes. But overall, the research reviewed suggests that switchgrass has carbon-sequestration advantages over other feedstocks, especially over row crops like corn that require more intensive cultivation.

There is one caveat: there's a lack of data concerning the effects of converting land for switchgrass cultivation. In the long term, it's unknown whether switchgrass crops would continue to have a positive net gain in greenhouse gas sequestration over the land it was converted from, as is suggested by shorter-term studies.

“Although switchgrass has recently received a lot attention as an environmentally beneficial energy crop, it is important to consider that switchgrass had not been planted as a monoculture crop until the mid-20th century,” Monti said. “Information needed to make long-term predictions on carbon sequestration, such as land use change, carbon turnover rate, and the economic lifecycle length are lacking."

What the research reviewed doesn't cover is whether producing biofuels with wild grasses is economically viable. We've been talking about switchgrass for some time now, and it generally looks like grasses are a cheaper feedstock than corn and sugar, even without the competitive economics that come into play as biofuel production grows.

The United States' total fuel ethanol output has grown every year since 1996, according to the Renewable Fuels Association. The RFA states that 13.2 billion gallons of fuel ethanol were produced in the U.S. last year; according to the EPA's Renewable Fuels Standard (RFS2), that number will eclipse 20 billion by 2015. In the U.S., corn is still by far the dominant feedstock used; a 2006 report from the USDA pegged corn-based ethanol at 97 percent of the total U.S. ethanol market, a figure that hasn't shifted dramatically since then. But it still can't compete with the yields that perennials like switchgrass offer: the Energy Department reports that corn grain offers a yield of 4.9 tons per acre per year, while perennials would offer eight tons per acre per year. That's a big difference, and it is even larger when you consider corn prices just starting to come down after a 15-year peak.

The issue still remains on the production side. The lignocellulose derived from grasses is still one of the most difficult cellulosic sources to convert to sugars for alcohol production. But technology to ease the process is in development.

Vinod Khosla wrote in a guest spot on GTM in January, "Though multiple cellulose and hemi-cellulose to sugars conversion technologies are in development, personally I am most bullish about some of the recent surprise developments in acid hydrolysis. At scale, HCL-like technologies should be able to produce food and non-food grade sugars at between $0.08 to 0.12 per pound at $50 per ton biomass costs," adding, "This or similar surprise technology developments could make biomass the new feedstock for sugars based processes."

The research suggests that switchgrass has a sequestration advantage over other crop-based feedstocks, and in the long term, its price advantage is likely to hold in the U.S. as corn demand increases. So is it time for switchgrass? Obama thinks so, but a more conservative outlook might be warranted until lignin-cracking technology is proven.