Lee Zeldin, administrator of the Environmental Protection Agency, told agricultural producers during a roundtable in Oklahoma that the agency is moving to roll back federal mandates tied to diesel exhaust fluid systems, arguing the requirements are overly burdensome for farmers during critical planting and harvest windows.
Diesel exhaust fluid (DEF) systems are used in modern diesel engines to reduce nitrogen oxide emissions under federal air quality rules. In agriculture, farmers have repeatedly raised concerns that system faults or “derates” can reduce engine power or shut equipment down during high-demand fieldwork, leading to costly delays during harvest.
Zeldin said the administration is working to dismantle those requirements, arguing they interfere with productivity in an already high-risk and low-margin industry.
“When a tractor goes down in the middle of a harvest, it results in lost time and lost money, great frustration, and a lot of these farmers are working to survive and working very hard to survive on extremely low margins. Sometimes the good years are shockingly lower margins than Americans who are not farmers may realize, and many of the bad years, you’re looking at farmers, really all across the country and here in Oklahoma, who actually don’t get a chance to pay themselves at all,” Zeldin said.
He said equipment failures tied to emissions systems can determine whether farmers are profitable in a given season and referenced ongoing federal efforts to address DEF-related performance restrictions.
“When a tractor goes down in the middle of harvest, it can be devastating and make the difference between making money that month or not. Heeding that call through my travels across all 50 states last year, last August, at the Iowa State Fair, we announced a significant reversal to the diesel exhaust fluid deratements. We then started working with manufacturers individually to have them update their software, work with their customers, and start getting the equipment updated to be able to prevent these significant, quick, massive deratements,” Zeldin said.
Zeldin said the agency has also taken steps involving engine manufacturers and emissions compliance data as it evaluates further regulatory changes.
“We then also issued a demand letter to 14 engine manufacturers that have 80 percent of the market to give us the information that they have on the DEF system failures. We received information from all 14 manufacturers. Using that information, we are now able to go further. In the meantime, at the end of March, President Donald Trump announced new guidance issued that day to get rid of the requirement for diesel exhaust fluid sensors altogether,” Zeldin said.
He added that additional internal enforcement and compliance actions are underway within the agency but have not been publicly released.
“There are other actions that EPA has been taking that haven’t been announced, but internally, within the agency, as it relates to our Office of Enforcement and Compliance. So, we desire to go as far as we possibly can pursuant to the law,” Zeldin said.
The comments come as agricultural producers continue to raise concerns nationally about equipment downtime, repair costs, and regulatory compliance burdens tied to emissions-control systems in modern diesel machinery. Farm groups have long argued that while emissions standards are intended to improve air quality, the real-world performance of DEF systems in field conditions can create operational risk during narrow harvest and planting windows.
