Iowa State University researchers have produced a harvesting system that gathers stover, the plant waste left after harvesting a crop, whilst simultaneously collecting corncobs. Stover is proving a successful source for fuel ethanol production.
That dual-stream, single-pass harvesting system was developed by Stuart Birrell, an Iowa State associate professor of agricultural and biosystems engineering, and graduate students Mark Dilts and Ben Schlesser.
The researchers are developing stover attachments that can be used on standard combines. The result would be an additional cost to farmers of about $10,000 to $15,000 instead of the six figures it would take for a separate combine to harvest stover. The attachments would also allow farmers to harvest grain and stover with one pass through a field.
The system includes a modified row crop header and corn reel attached to the front of the combine and a chopper and blower attached to the back. The header and reel feed leaves and stalks into the combine so the biomass can be harvested before it touches the ground and is contaminated with soil. The chopper cuts stover into 2-inch pieces. And the blower throws the chopped stover into a wagon.
Birrell's stover harvesting research has been supported by a three-year, $180,000 grant from the US Department of Agriculture and the US Department of Energy and a two-year, $50,000 grant from agricultural equipment manufacturer Deere & Company.
Birrell said development of a stover harvesting system has been constrained by a lack of research funding.
‘Significant resources have been dedicated to the process of converting cellulose into ethanol,’ he said. ‘But very little has gone into answering how do you get a supply of stover from the field to the biorefinery. This will be critical to the success of the bioeconomy.’