Pre-winter switchgrass harvest produces better ethanol yields

In Michigan, researchers from Michigan Technological University, University of Tennessee, University of Wisconsin-Madison and Michigan State University are looking at Wisconsin switchgrass to better understand the costs and benefits to harvesting at various points in the season. Comparing data from samples collected every two to three weeks from the switchgrass fields against biofuel yield data from each site, Ong discovered that as the crop aged past senescence, the point at which plants begin to go dormant for the winter, ethanol yields from the harvested crop became more efficient rather than less so.

“Most of the time people say ‘harvest early, get the highest conversions,’ but no one has taken it through fermentation to see what the microbes do in the process,” said Rebecca Ong, assistant professor of chemical engineering. “Previously, people had been saying ‘Well, you can harvest any time. Earlier is better [for processing], but you can really harvest any time.’ And what we’re finding is that this may not be true. So, you may have a more limited harvest window than we were expecting.”

The work is part of the Great Lakes Bioenergy Research Center.