Study: Milling Switchgrass Waste of Money?

WEST LAFAYETTE, Ind., April 15 (UPI) — A Purdue University study suggests biofuel processors milling switchgrass to help its flowability can save money by not doing so.

Assistant Professor Klein Ileleji said switchgrass becomes a problem when processors try to move it into boilers. That’s because switchgrass is shaped like matchsticks, causing pieces to interlock and disrupt its ability to flow. Ileleji said such blockages cost time and can be dangerous for those tasked with breaking the clog.


“In any facility — in a power plant or in a processing facility — when you have a blockage, it’s a processing nightmare,” said Ileleji.

Conventional wisdom holds grinding switchgrass into smaller pieces brings its aspect ratio closer to that of corn and soybeans, which have no flowability problems.

But Ileleji disagrees.

“Grinding does not necessarily change the morphological characteristics in switchgrass that are important for flow,” he said.

Ileleji said testing showed hammermilling, which beats biomass until it’s small enough to pass through screens, breaks switchgrass in a way that keeps its aspect ratio about the same regardless of size. And those high aspect ratios still keep causing switchgrass to interlock and clog in bulk flow.

Ileleji said processors could save money with the information because they can stop hammermilling switchgrass and save high energy costs.

The study that included doctoral student Cedric Ogden appears in the journal Transactions of the American Society of Agriculture and Biological Engineers.

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