The Ups and Downs of Our Time

Legislation to roll back diesel-emissions regulations advancing through Congress is not in the public interest.

Finally, it happened. After months of labor, U.S. EPA delivered a robust growth-oriented renewable fuels policy setting biobased fuels on a path to take over about 10 percent of the total distillate-fuel pool by 2028.

Kudos to all of us that pushed so hard for so long to get it done, especially growers’ groups and Clean Fuels Alliance America. It was a team effort. Now it is time to deliver.

The biobased fuel growth trajectory comes at an interesting time as war with Iran has crimped global oil supply through the Strait of Hormuz, raising traditional U.S. fuel prices to record levels—with diesel fuel spiking at over $7 a gallon in California. High fuel and fertilizer prices are hitting farmers hard at the worst possible time as planting season is underway. More biofuels in the fuel pool can help mitigate some of the price shocks of petroleum diesel at the pump but producing that fuel now faces those same challenges. It’s like rain when the sun is shining.

Engine manufacturers are experiencing their own bout of stormy weather, having to defend technology that has been proven for 15-plus years and the success story of cleaner air and engines that are more powerful and fuel efficient. A decade and a half ago, a new emissions-control technology was introduced to achieve tightening EPA emissions standards that required a 90 percent reduction in emissions of nitrogen oxides (NOx). That technology—known as selective catalytic reduction (SCR)—is now standard on all heavy-duty diesel trucks and about half of all farm equipment. It’s an active system that requires replenishment of diesel exhaust fluid (DEF), which is 32 percent aqueous urea, at a rate of around 2 percent to 3 percent based on fuel consumption. Beyond the clean-air benefits, it yields greater fuel economy and better performance as well.

A little over a year ago, concerns from truckers and farmers about problems with SCR and DEF systems made their way to EPA. The systems are designed such that if DEF has not been refilled, it triggers a fault within the emissions-control system, and a progressive series of measures (inducements) kick in. Progressive dashboard-warning lights ultimately end with engine-power derating or inability to start until repaired. These measures are insurance policies to protect the engine and ensure it achieves EPA-certified emissions levels. SCR systems rely on a series of sensors to ensure the presence and quality of DEF and the real-time NOx emissions downstream in the exhaust—in other words, to confirm whether the system is truly reducing emissions.

Failures of sensors and other issues can ultimately result in the untimely derating of engines or shutdowns altogether. EPA responded with two sets of guidance for manufacturers (August 2025 and March 2026) to make adjustments in their compliance strategies for both new and existing engines and equipment. This will eliminate the most aggressive inducements and give significantly more time for farmers to refill DEF or to diagnose and repair a problem. The most recent guidance relieves manufacturers from having to use DEF quality sensors, which were identified to be a leading source of the reported problems.

Just as manufacturers are adjusting their compliance strategy, Congress gets involved. Hearings were held and now multiple pieces of legislation are in play. These range from a measure to eliminate DEF requirements in extremely cold climates put forth by Sen. Dan Sullivan, R-Alaska, to a bill from Rep. Victoria Spartz, R-Indiana, which eliminates emissions standards from farm equipment altogether—now included in the House-passed farm bill. It’s a 9-1-1 moment. With much invested in clean air and greater sustainability, eliminating engine-emissions standards is not in the public interest.

Fuels interests and engine makers have had their differences over the years, but they have ridden out many difficult policy challenges together—ultra-low sulfur diesel fuel and some early biodiesel mandates come to mind. But the two industries have come closer over the past decade thanks in large part to the quality commitment of the biodiesel industry and customer demand for more sustainable fuels. More manufacturers outwardly embrace biobased diesel fuels and, as John Deere has recently announced, higher blends of those fuels (B30), which send a strong signal about that relationship.

The fate and future of engine makers and fuel producers are inextricably linked. More sustainable engines using more renewable fuels lifts us up. Policies that diminish sustainability and clean air take us downward. The path is now more uneven than ever, much like the weather—one minute it is sunny and the next it is pouring rain. The only thing we can do is dress appropriately.

Author: Allen Schaeffer

Executive Director

Engine Technology Forum

301-668-7230

aschaeffer@enginetechforum.org