The impact of harvesting corn stover on the quality of farmland (nutrients, compaction, subsequent grain yield) is not yet fully understood, Schlicher says. Farmers will need to think about erosion as they remove stover from the field.

They also must understand that feedstocks need to be very clean going into the process, explains Mike Duffy, agricultural economist, Iowa State University (ISU). “Otherwise, it will interfere with the enzymatic process,” he says.

Farmers will have a narrow window in which to first harvest grain and then harvest stover, although some work is being done to develop one-pass systems. Researchers at ISU, for example, are developing a single-pass harvesting system that will gather corn into the hopper while blowing stover into a wagon following behind.

Without such a one-pass system, farmers will need to harvest grain, then windrow and bale stover. “We will need to learn more about what kinds of bales work best,” Tyner says.