The cost of harvesting and storing switchgrass in round vs. large square bales is being studied by University of Tennessee scientists as cellulosic facilities are being built in the state.

Unsurprisingly, dry-matter losses “are significant on square bales when they're not covered,” says Burt English, University of Tennessee economist, of preliminary findings.

English, ag economist Jim Larson and soil scientist Don Tyler evaluated 5 × 4' bales from a John Deere round baler and 4 × 4 × 8' bales from a Massey Ferguson square baler. They observed quality, handling and storage costs of round bales on the ground and both types of bales on pallets and on gravel. Both bale types were tarped with plastic or untarped.

Results after opening three bales of each of these treatments at zero, 100, 200 and 300 days after harvest have been recorded. “We're going out to 500 days because we think some bales may have to be stored longer than a year to guarantee that the plant has enough material to operate year-long,” English says.

“We're taking information on those bales at those intervals, then sending it through wet chemistry analysis to get information on how much ethanol they will provide.”

Those test results aren't back, but English learned that uncovered square bales suffer dry-matter losses of up to 50% after 200 days and become difficult to move. “When they're covered, losses are at 20-25%.

“Round bales have fewer losses regardless of whether they're covered or not covered, but covered bales have 8-12% dry-matter losses under covered conditions.”

The round baler, at a 5-ton/hour harvest capacity, cost $23,000; the square baler, at a 12-ton/hour harvest capacity, was priced at $87,000.

The cost of baling and stacking round bales (with a bale spear one bale at a time) was $17/ton at 100, 200 and 300 acres. But square-bale harvest and stacking costs (two bales per trip) declined from over $14/ton at 100 acres to $12.50/ton at 200 acres and $12/ton at 300 acres.

Storage cost to cover 144 square bales or 120 round bales with 25 x 100' tarps was $502. A pallet cost $6.50 and could hold two square bales or one round bale. Stored on gravel with a textile pad, square bales covered 1,900 sq ft and round bales, 2,000 sq ft, for 60¢/sq ft. The cost of two laborers to tarp and lay pallets was figured at $9.75/hour.

“Going from field to plant, square bales are more efficient than round bales. But square balers cost three or three and a half times more than round balers,” English observes.

Round bales are more cost-efficient if switchgrass has to be stored. If storage isn't needed, square bales have the advantage, he says.

“If you harvest from November to March and the plant consumes bales as they're harvested, those could come in as square and the rest of the supply could be stored in round bales. That's from a cost standpoint. If the cost of handling two kinds of bales at the plant exceeds the dry-matter cost or the cost gained from that switch, you'd probably want to go with all round bales,” he says.