Ahead of what’s sure to be a tough planting season, some farmers frustrated by in-field equipment shutdowns due to fragile diesel exhaust fluid systems might feel like they’ve received a leg up from the Environmental Protection Agency, which removed DEF sensor requirements from all diesel vehicles on March 27.
“Manufacturers welcome the new guidance by the EPA that provides them with new options in the selective catalytic reduction [SCR] systems to utilize NOx sensors instead of urea-quality sensors as part of their compliance strategy,” said Allen Schaeffer, executive director of the nonprofit Engine Technology Forum.
Machinery’s catalytic reduction systems inject DEF into exhaust streams to neutralize harmful pollutants from diesel engines. EPA’s primary argument for removing the DEF sensor requirement is threefold:
- Failing systems are dangerous.
- Productivity is lost.
- Inaccurate sensor readings can shut machines down.
Farmers who support rollbacks say emission reduction systems make already expensive farm machines unnecessarily complex, shorten their lifespan and are expensive to repair, especially during critical planting or harvest windows.
Citing manufacturer data provided to EPA ahead of the new guidance, Schaeffer said urea-quality sensors, which ensure DEF tanks don’t have water in them, “were responsible for a large majority of failures and warranty claims. These units can fail due to a variety of conditions — crystallization of DEF on the sensor, freezing conditions, temperature gradients, mechanical stress due to vibration [and] faulty level sensing that renders a full system fault.”
The sensors were initially required to ensure operators weren’t using substances other than DEF.
In a statement about the changes, EPA Administrator Lee Zeldin touted $4.4 billion in farmer savings annually, stressing that farmers everywhere experience downtime when sensors fail.
“I have heard from truck drivers, farmers and many others complaining about DEF and pleading for a fix in all 50 states I visited during my first year,” Zeldin said.
If a system becomes inaccurate and fails, the new ruling lets manufacturers remove urea-quality sensors and switch to nitrous oxide sensors. It also affirms that operators can install approved nitrous oxide sensor-based software without facing illegal tampering repercussions under the Clean Air Act.
The statement notes that EPA anticipates its changes “will greatly curb errors that traditional sensor technologies have been prone to and reduce the issues Americans face with inaccurate DEF failures.”
Other updates
Beyond legality, previous guidance from the Trump administration through EPA only requires warning lights to be illuminated for 650 miles or 10 hours after a fault is detected. After that, the engine will only mildly derate, letting drivers operate normally and without speed limits for up to 4,200 miles, or two work weeks.
The speed will then drop to 25 mph until repairs are made. Non-road equipment won’t be impacted at all for the first 36 hours before a slight torque reduction takes effect, according to the statement. Previously, DEF systems forced a vehicle to drastically reduce speed or stop altogether when there was a mechanical failure or fluid ran out.
Schaeffer said manufacturers are assessing the March 27 ruling to see if their compliance plans must shift more toward NOx emissions sensors and away from DEF‑quality sensors.
“There is not a uniform approach to compliance within manufacturers or classes of engines and equipment, and their different sensing approaches and vendors,” he said. “Manufacturers have to look at changes to new products coming together today, as well as how the guidance will be implemented retroactively to existing engines and equipment.”
Schaeffer noted that existing 2014 emissions standards that govern allowable levels of emissions from new engines have not changed.
“It is important to underscore this as a number of news outlets have incorrectly reported that President Trump is getting rid of DEF or diesel emissions standards. This is not the case,” he said, blaming social media influencers and commentators for spreading those statements.
“We should not lose sight of two important aspects of SCR and DEF,” he said. “One, they enable greater fuel efficiency in products with SCR systems compared to previous generations — saving farmers money. And two, they have contributed substantially to the clean air progress we all enjoy today in the form of air that increasingly meets the health-based clean air standards.”