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Roush CleanTech has introduced ultra-low NOx propane autogas engines that are 90% cleaner than mandated U.S. EPA standards. Shown is Roush technology on display at the 2019 Work Truck Show. (Ryan Gehm)

Renewable propane, ultra-low NOx engines set standards for propane autogas innovations

The future of trucking is looking even greener. Not only are companies forced to contend with new government regulations to meet lower emissions and increased CAFE standards, but pressure from communities and customers is requiring many companies to make the switch to alternative fuels, including propane autogas. Over the past four decades, propane autogas has emerged as a proven alternative fuel. With more than 200,000 propane autogas vehicles on the road in the U.S., fleets of all types and sizes are making the switch to this alternative fuel.

Just as the future of trucking is changing, propane autogas is changing the future for many fleets. New innovations, including ultra-low NOx (nitrogen oxide) engines and renewable propane, are raising the bar for what it means to be a clean fuel for fleets.

Ultra-low NOx engine innovation
In 2018, Roush CleanTech and Greenkraft, Inc. introduced ultra-low NOx propane autogas engines that are 90% cleaner than mandated U.S. EPA standards and certified to the optional ultra-low NOx emissions standard as defined by the California Air Resources Board (CARB) for heavy-duty engines with 0.02 grams per brake horsepower-hour. The new engine technology is classified as near-zero emissions and has moved propane autogas even closer to achieving zero emissions levels.

Propane autogas is proving to be an environmental and economic bonus for fleet owners in other ways. The $2.7 billion Volkswagen Mitigation Settlement includes funding for Class 4-7 medium- and heavy-duty trucks and many owners are applying and qualifying for new or replacement vehicle funding. Propane autogas ultra-low NOx engines are the most cost-effective fuel solution for reducing NOx emissions, which is the primary target of the VW Settlement.

Mitigation plans in most states are finalized and the application and awards process is well under way. For more information about state mitigation plans, visit Propane Education & Research Council’s (PERC) Volkswagen Trust Resource Center:

Renewable propane production growing
Ultra-low NOx engines are proving to be a cost-effective choice for many fleets, but it is only one of the cutting-edge solutions available for internal combustion engines today. Renewable propane is now available and will be a fuel that advances propane autogas well into the future.

Renewable propane is a byproduct of the renewable diesel and jet fuel production process, which converts plant and vegetable oils, waste greases and animal fat into fuel. The renewable fuel is currently produced in U.S. refineries in California, Texas and Louisiana as part of their renewable diesel production systems. The process utilizes existing infrastructure which is required to produce renewable diesel. Renewable propane production begins with a biological product rather than a fossil fuel and the existing refinery processing systems are used to develop a biologically sourced fuel that is identical in performance to traditional propane. Worldwide output is currently estimated at 100MM gal. With new cellulosic sources, many experts say the entire worldwide demand can be met with renewable propane by 2040.

Because renewable propane’s chemical structure and physical properties are the same as propane produced from fossil fuels, renewable propane behaves in the same way as propane autogas, providing fleet owners the same performance and reliability they rely on. At the point of combustion, renewable propane is carbon neutral, meaning no new carbon is added to the atmosphere with the fuel during combustion. Renewable propane produces fewer lifecycle carbon-dioxide emissions than propane sourced from fossil fuels.

Renewable propane is identical in state to natural propane, which means it can be used in any existing propane autogas engines. Combining the new ultra-low NOx engine powered by renewable propane reduces emissions levels to near-zero and sets a new standard for the transportation industry as far as what it means to be clean. These innovations are tremendously important, as the future of engine fuels continues to aggressively move to zero emissions.

To learn more about propane autogas vehicles, visit

Michael Taylor, director of autogas business development for the Propane Education & Research Council, wrote this article for Truck & Off-Highway Engineering. He can be reached at

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