Crookston, Minn. — This past summer, AURI scientist Edward Wene and other researchers investigating biomass sources for energy, were harvesting switch-grass from a test plot near Fertile, Minn. They noticed an adjacent stand of tall, dense grass — prairie cord-grass, which had been planted by a local company for seed. The team got permission to harvest a sample for yield comparison.
The results took them by surprise — they may have uncovered a potential crop for making cellulosic ethanol and other biofuels.
Wene, Wendell Johnson of the University of Minnesota-Crookston and Bill Berguson of the Natural Resources Research Institute have been establishing switch-grass test plots to compare fertilizer rates and biomass yields, so producers can assess production costs. In 2007, plots near Thief River Falls, Minn. averaged 2.5 dry tons of biomass per acre while the Fertile fields averaged 4.8 tons.
Meanwhile, the cord-grass plantation averaged 6.8 dry tons per acre.
“This wasn’t a discovery of an unknown crop, but nonetheless the yields were impressive,” Wene says. “Now we need to find out if that was just a really good field — last year was a very good year (for growing cord-grass) — or if we’re onto something.”
Building on biomass
Developing cellulosic ethanol from biomass, including crops like switch-grass, is gaining tremendous national attention. Wene says switch-grass became the biomass focus crop in the 1970s because it can be grown nearly everywhere in the country. That doesn’t mean it’s the best crop for producing biomass. “Other plants may do better regionally,” Wene says.
Prairie cord-grass is a native grass that can grow 6 to 8 feet tall. It’s found throughout the Northeast, Great Lakes and the Midwest — typically in poorly-drained and wet soils, ditches, marshes, streams and potholes. Wene says it’s not a suitable forage crop but the impressive northern Minnesota yields are generating interest in evaluating it as a biomass-fuel crop.
“We can’t say that it’s the crop of the future because at this point all we can verify are yields from one field.” But, Wene adds, “they are higher yields than we’ve seen from anything else in this area.”
Wene cautions that yields aren’t the whole story. Little is known about the cost of production, biomass storage, seed viability, weed control or a host of other production issues. But prairie cord-grass appears to be a biomass crop that merits further exploration.