Giant miscanthus can produce more than double the biomass per acre as corn, according to Tim Mies, director of a 320-acre Energy Farm at the University of Illinois’ South Farms.
“It does this apparently without the need for any nitrogen fertilizer, very few other inputs and it adds significant amounts of organic matter to the soil. So miscanthus might be a third crop for Illinois, and one particularly suited to marginal land,” says Mies.
But miscanthus doesn’t lend itself to producing seed on an agronomic scale. Because it is a sterile crop, rhizomes need to be dug up, broken apart and replanted into new fields. “Miscanthus planting is currently a very labor-intensive operation,” he says. “Rather like harvesting and then planting potatoes.”
Currently, U of I researchers are working to develop machinery that can efficiently harvest and plant the rhizomes. “Potato-handling equipment is something we’ve been looking at because it can physically go into the dirt and lift out the material,” Mies says.
Researchers at the university’s Energy Farm, devoted to studying potential biofuel crops, are also looking into restored prairie as an energy crop. “If we’re going to convert marginal land back to grasses, restored prairie has the potential to be a possible biomass source,” Mies says.
Restored prairie is a mixture of tall grasses and small nitrogen fixers. It would be harvested as a crop in the early winter when nutrients have been cycled back to the roots. “In theory, it makes a lot of sense to convert the land back to what it used to be, but how that might translate on an agronomic scale is yet to be seen.”
One challenge in growing restored prairie as a biomass crop: It can be choked out by more-aggressive weeds. “There isn’t an herbicide you can use to control the weeds because something that would kill off the weed would also kill the plants that you want,” Mies says.
Being a mixture of plants, restored prairie is inconsistent, which could make its harvested biomass difficult to process into ethanol.