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EPA targets DEF system problems after farmers report costly shutdowns

A southeast Kansas farmer says he’s relieved that the U.S. EPA is taking steps to address long-standing concerns about DEF system failures.

“They’re just so unreliable.”

Ben Bellar says an issue with his combine this fall cost him thousands of dollars and time in the field. “An emissions failure will completely shut you down and de-rate you. I had to wait for the local dealer to come out and physically fix this combine. We were dead in the water. There was nothing we could do except limp it to the road and that was about it.”

Recently, EPA announced its investigating system failures by “demanding” information from equipment manufactures.In August of 2025, the agency issued guidance urging manufacturers to revise DEF system software.

Bellar owns a trucking company and says the problem extends beyond farmers and can impact the transportation of ag goods. He says emission requirements can be hit-or-miss. “There’s still some hiccups. We have new semi-truck that keeps popping injectors and needing the injectors replaced because of unknown reasons, but these injectors have been so finely tuned to limit the amount of soot coming out of engines.”

He says he supports cleaner, more efficient engines, but believes equipment shouldn’t be sidelined by software-related shutdowns.

Administrator Lee Zeldin says this is a massive issue and the Trump administration is committed to ending unnecessary frustrations in the industry.

In a statement to Brownfield, The Association of Equipment Manufactures says the new guidance will help resolve longstanding ambiguity around when emission overrides are permissible.

Farm equipment manufacturer CLAAS, who doesn’t build engines, declined an interview request from Brownfield.