This combine-baler combination machine reduces ash contamination and the cost of harvesting biomass for cellulosic ethanol plants, says Iowa State's Matt Darr.
Most of the equipment is in place to efficiently harvest and deliver the massive amounts of biomass required by cellulosic ethanol plants, says Matt Darr, Iowa State University ag engineer.
Needed, though, are faster methods for loading, unloading and securing the thousands of truckloads that each plant will demand annually, says Darr.
He and his research team have been evaluating biomass harvesting, hauling and storage methods for several years, focusing on corn stover. Stover will be the primary feedstock for Poet-DSM’s Project Liberty at Emmetsburg, IA, and the Abengoa Bioenergy Biomass facility in Hugoton, KS, both set to begin commercial production late this year. DuPont’s Nevada (IA) Cellulosic Ethanol Facility, expected to open in 2014, will also use stover.
Darr calls corn stover “the dirtiest and hardest material out there to bale.” It’s often more than 10% ash and doesn’t bind well, two factors that add stress to balers. Today’s balers can handle it, but maintenance costs will be higher than with most other forages, says Darr.
From biomass delivery through conversion into fuel, excess ash also increases costs for cellulosic ethanol companies. To reduce ash contamination and labor requirements, Darr and his colleagues developed the combine-baler combination now marketed by Agco. It bales stover as it leaves the combine so it doesn’t touch the ground (see "Combine-Baler: Same-Pass Biomass Baling").
The engineers found that harvesting grain and stover at the same time reduces the combine’s capacity by 15-20%. But it still can thresh almost 3,000 bu/hour, more than most grain-handling systems can handle.
“Single-pass machinery is showing a lot of promise as one of the long-term solutions for industrial biofuels,” says Darr.
The Agco baler makes large square bales, the type preferred by biofuel companies. Of the three companies currently buying stover, Poet-DSM is the only one accepting round bales.
Semi flatbeds are well-suited for quickly moving large numbers of biomass bales, and thanks to new high- and extra-density large square balers, they can be loaded almost to their weight limits. But moving the bales onto and off of trucks must be done more quickly, he says. The Poet-DSM plant, for example, will require about 18,000 semi loads of biomass per year.
“When you think about that many trucks, it’s not the over-the-road time that has the most cost. It’s the loading and unloading and strapping and securing and making sure you do that in a very safe way where most of the cost is incurred.”
He mentions an automatic load securement system recently introduced by Stinger Inc. as the type of development needed.
“These are really critical innovations to make this supply chain a reality,” Darr says. “And they’re needed, not only to deliver to the plant, but also to handle the fall activities out of the field and into a satellite storage facility.”
Due to the volume required, biofuel companies want bales with consistent dimensions that hold together when handled multiple times. The equipment for making and moving them is expensive, so much of the work likely will be done by custom harvesters. However, some corn growers may be able to justify the expense, given the fact that, besides the direct income from stover sales, harvesting some stover increases corn yields, especially in continuous cornfields.
Darr has found that the yield gain from partial stover removal averages 3.5%, or just over 6 bu/acre when the average yield is 185 bu/acre. That comes to $42/acre if corn is worth $7/bu.
“So pretty quickly it starts adding up to some real dollars,” he says.