Progress is being made toward developing cost-effective processes for harvesting biomass crops. So say University of Illinois ag engineer Alan Hansen and colleagues working with the Energy Biosciences Institute to determine the main obstacles in current processes and equipment that could limit their application in biomass feedstock harvesting.
“Part of our work is to assess how well existing equipment functions and what modifications we need to make to this equipment to ensure that it can handle miscanthus harvesting adequately,” says Hansen. “These machines are generally set up to harvest crops like hay and forage. There is some degree of uncertainty related to these machines working in miscanthus, which is a much denser, taller crop, or even switchgrass, a shorter grass.”
“In some of our earlier work with miscanthus, the mower-conditioner was not set up well,” he says. “So after the miscanthus stems were cut, instead of being mashed up, they came straight out the back, all lined up, and it was difficult for the baler to pick up that material.”
The researchers experimented with sickle and disk mowers, eventually choosing a disk machine because its through-put is much greater. “But there were challenges with that in that you have an auger that propels all the cut material to the center of the head to then feed it out the back. The auger wasn’t doing a very good job of picking up these long stems after they were cut. So they had to add some fingers and vanes to help with that process. They also changed the size of the auger in order to help propel the material more efficiently into the center of the machine.”
After the changes were made, “The system seemed to work well, but we haven’t had a solid opportunity to evaluate the performance, so we will be able to do that in the coming harvesting season,” says Hansen.
Data-logging systems are fitted to the mower-conditioner to track its performance in the field. “We use GPS to capture information about the instantaneous location of the machine; we can also monitor how much power is being used, how fast the machine is going, how the engine is performing, things that allow us to evaluate how effective the machine is at harvesting the biomass.”
The researchers also collect data on the baler. “Ultimately, we would like to know, for each bale that is generated, the weight of the bale and where it ends up being placed in the field,” Hansen says. “We can then use that as a basis to map the yield.”
He says they’re currently exploring the development of what he calls a “look-ahead” sensor. “When an operator runs a machine through the field, they have to set the speed based on their judgment about the amount of biomass there is ahead of the machine. It takes a couple of runs to get a sense of what that is. If we can judge the size and density of a plant – and thus the yield – we can provide that information to the operator, who can then adjust the speed of the machine. And beyond that, we can use it as a basis of automatically controlling the speed of the machine.
“We’ve done some field trials, not on the machine per se, but stationary trials, where we look ahead at the crop and do an assessment. So this could be a very useful sensor,” he concludes. “It looks promising.”