CARB Certifies Next-Generation Propane Engine in Blue Bird School Buses to Lowest NOx in Market

ROUSH CleanTech first to earn the optional ultra-low nitrogen oxide CARB certification for 2022 model year with its Gen 5 propane engine


  • ROUSH CleanTech is first OEM to receive CARB’s 0.02 grams per brake horsepower-hour (g/bhp-hr) certification for 2022 model year.
  • The company’s propane engine is 90% cleaner than national emissions requirements and achieves 2027 proposed standards on NOx.
  • Blue Bird propane school buses equipped with ultra-low NOx engines will provide multiple advantages for school districts and school bus contractors seeking funding from the Infrastructure Investment and Jobs Act’s $2.5 billion Clean School Bus Program.

ROUSH CleanTech is the first original equipment manufacturer to receive California Air Resources Board’s 0.02 grams per brake horsepower-hour certification for 2022 model year vehicles. The optional ultra-low CARB certification is 90% cleaner than current emissions standards for nitrogen oxides.

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The new engine certification covers ROUSH CleanTech Gen 5 propane engines for Blue Bird school buses.

Propane is well established as an economical, clean and domestically produced alternative fuel for school buses. “Blue Bird is the leader in clean emissions school buses with over a decade of selling experience, and more than 20,000 clean and cost-reducing propane school buses on the road,” said Matthew Stevenson, president and CEO of Blue Bird Corporation. “Equipping our buses with the lowest nitrogen oxide propane engine is great news for the environment, our customers and our children.”

Nitrogen oxides, known as NOx, are a group of gases known as a primary contributor to acid rain, smog and other air quality issues. According to the Environmental Protection Agency, exposure to NOx can trigger health problems, such as asthma and other respiratory issues, especially in children.

“Since the introduction of our Ford 7.3L V8 propane engine in 2020, our team has worked tirelessly to gain this emissions certification,” said Todd Mouw, president of ROUSH CleanTech. “We remain committed to providing cost-efficient, advanced vehicle solutions for the school bus market that reduce environmental impact.”

This is the second time ROUSH CleanTech has earned the ultra-low NOx certification, previously for its 6.8L V10 propane engine in 2018. The certification is part of a proposed federal emissions regulation that goes into effect in 2027. “We didn’t wait for the regulation to go into law. We’ve already achieved it,” Mouw added.

Blue Bird propane school buses equipped with the ultra-low NOx engines will provide school districts and school bus contractors multiple advantages in seeking funding from the new Infrastructure Investment and Jobs Act’s Clean School Bus Program. The provision provides $2.5 billion for the purchase of low- and zero-emission school buses, including propane which is identified in the legislation as an emerging alternative fuel. Funding is slated to be released beginning in 2022 and continuing through 2026, with project implementation as soon as next year.

About Blue Bird Corporation: Blue Bird (Nasdaq: BLBD) is the leading independent designer and manufacturer of school buses, with more than 550,000 buses sold since its formation in 1927 and approximately 180,000 buses in operation today. Blue Bird’s longevity and reputation in the school bus industry have made it an iconic American brand. Blue Bird distinguishes itself from its principal competitors by its singular focus on the design, engineering, manufacture and sale of school buses and related parts. As the only manufacturer of chassis and body production specifically designed for school bus applications, Blue Bird is recognized as an industry leader for school bus innovation, safety, product quality/reliability/durability, operating costs and drivability. In addition, Blue Bird is the market leader in alternative fuel applications with its propane-powered, electric and compressed natural gas-powered school buses. Blue Bird manufactures school buses at two facilities in Fort Valley, Georgia. Its Micro Bird joint venture operates a manufacturing facility in Drummondville, Quebec, Canada. Service and after-market parts are distributed from Blue Bird’s parts distribution center located in Delaware, Ohio. For more information on Blue Bird’s complete line of buses, visit

About ROUSH CleanTech: ROUSH CleanTech, an industry leader of advanced clean transportation solutions, is a division of the global engineering company Roush Enterprises. ROUSH CleanTech develops propane autogas and electric propulsion technology for medium-duty Ford commercial vehicles and school buses. With more than 37,000 vehicles on the road, the Livonia, Michigan-based company delivers economical, emissions-reducing options for fleets across North America. Learn more at or by calling 800.59.ROUSH.


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