Four myths about “clean” diesel school buses

Recent claims within the school bus industry state that diesel buses are clean, cost-effective and easier to maintain — while casting doubt on propane autogas. Here are some of those recent statements made about “clean” diesel school buses — and the facts about propane-fueled models.

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A Blue Bird Vision bus powered by Liquefied Propane Gas (LPG). There are over 10,500 Blue Bird Vision Propane buses in operation across North America.
A Blue Bird Vision bus powered by Liquefied Propane Gas (LPG). There are over 10,500 Blue Bird Vision Propane buses in operation across North America.

1Fiction: Diesel is clean and has the lowest carbon footprint over the operational life of a school bus.

A Blue Bird Vision bus powered by Liquefied Propane Gas (LPG).

Fact: Modern diesel emissions are much cleaner than they used to be and typically do well in terms of greenhouse gas emissions. Propane engines also have very low greenhouse gas emissions — and also significantly reduce the toxic emission constituent of nitrogen oxides (NOx) at four times less output than modern diesels. This is important because most NOx emissions are sourced from the transportation sector whereas only a small percentage of greenhouse gas emissions are sourced from transportation. Greenhouse gas emissions like carbon dioxide are inert gases and are part of what we exhale. NOx pose considerable danger to human health and air quality.

“Propane is definitely the direction to go, away from diesel and emission issues,” said Neal Higgins, mechanic for Bibb County School District in Macon, Georgia.

2Fiction: Diesel buses are easier to maintain.

ROUSH CleanTech technicians discuss the benefits of propane-fueled school buses. There are over 10,500 Blue Bird Vision Propane buses in operation across North America.

Fact: Today’s diesel buses may be cleaner than year’s past, but they are cleaner only through complexity, like expensive equipment and high-maintenance systems, which aren’t required on propane autogas school buses. To meet federal emission standards, a diesel bus has 20 additional parts — that’s 20 components that need to be maintained. They include diesel particulate filters, manual regeneration and diesel exhaust fluid, and other complex after-treatment devices.

“There are a lot of hoops you have to jump through with diesel due to of all of the EPA emission standards. New EPA-certified diesel buses have become much more expensive and difficult to maintain,” said Bruce Thomas, master technician for Adams 12 Five Star in Thornton, Colorado. “For our district, the upfront costs have increased substantially just for equipment to pass newer emission standards.”

3Fiction: When you look at all the factors, diesel buses offer the lowest total cost of ownership.

ROUSH CleanTech technicians discuss the benefits of propane-fueled school buses. There are over 10,500 Blue Bird Vision Propane buses in operation across North America.

Fact: More than 800 school districts are saving 20 to 50 percent on a cost per mile basis for fuel and maintenance operating propane buses compared to diesel. School bus fleets have saved between $400 and $3,000 per propane bus per year when compared to the diesel buses they operate. Propane has the lowest cost of infrastructure of all transportation fuels, saving money on fueling station needs. Historically, propane autogas averages 50 percent less than diesel.

“We tracked data on both a propane bus and a diesel bus of the same model year. The propane bus was driven for bus routes on dirt roads with multiple stops and starts,” said Brian Swestaka, director of transportation for Howard-Winneshiek Community School District in Cresco, Iowa. “The diesel bus was used as an activity bus, mostly highway miles. The propane bus still operated significantly cheaper than the diesel bus due to fuel and maintenance savings.”

4Fiction: Many alternative fuel engines aren’t built for medium-duty use.

ROUSH CleanTech technicians discuss the benefits of propane-fueled school buses. There are over 10,500 Blue Bird Vision Propane buses in operation across North America.

Fact: The Ford 6.8L engine is built specifically for medium-duty applications. Introduced in 1997, there are more than 1.8 million of these engines on the road today. This is the engine used in more than 10,500 Blue Bird Vision Propane school buses transporting students to and from schools across the nation.

While there is an upfront cost associated with converting a vehicle or buying a new dedicated propane autogas model, the low cost of the fuel compared with diesel often translates to a quick return on investment. Most fleets that make the switch recoup their investment within 18 months of use.

“A state grant paid for the incremental cost difference of our propane buses, which meant we could start saving money right away since our fuel and maintenance costs are much lower than with our diesel buses,” said Ricky Phillips, vehicle maintenance manager of Clarksville-Montgomery School District in Montgomery County, Tennessee.

Whatever type of fuel used, school districts around the nation must work within their operational budgets and environmental goals. Hundreds of school districts have chosen propane and are proving it’s a clean-burning and economical transportation fuel.

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