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Back to School Lessons on Buses

    Replacing the oldest diesel buses with the new generation buses can reduce emissions and improve fuel efficiency, as well as all the safety advantages of new buses

    Example of caption textIn a few weeks, about half a million yellow buses will be on the roads signaling the start to the new school year.

    Nationwide 91% of all school buses run on diesel power. Diesel has long been the technology of choice because its combination of features: fuel safety in crashes (diesel is less combustible than other fuels), fuel efficiency, reliability, performance, driving range, durability, resale value, as well as its easy access to fueling, servicing and maintenance.

    Electric and compressed natural gas each register less than 1% in school buses, according to the Diesel Technology Forum’s analysis of data sourced from S&P Global Mobility TIPNet data of vehicles in operation for Class 3-8 as of December 2021. Even though these fuels make up a small fraction of school buses, they just got a major boost from public funding in the Bipartisan Infrastructure Law that will provide $5 billion over the next five years (FY 2022-2026) to replace existing school buses with zero-emission and low-emission models.

    Of the diesel portion of the school bus fleet, approximately 72% of buses in operation have at least particulate trap technology. A total of 58% of the nation’s buses are of the newest generation of advanced diesel technology equipped with both particulate filters and selective catalytic reduction systems.

    According to the most recent evaluation of the health effects performance of this new generation of diesel technology from the Health Effects Institute, the emissions from advanced heavy-duty diesel technology engines were well below regulatory standards. Thanks to the advanced filters and selective catalytic reduction systems, harmful emissions and health-effects related concerns from previous generations of vehicles without these technologies were nearly eliminated.

    New natural gas and diesel buses are close in emission levels, with natural gas slightly better in terms of nitrogen oxide emissions. While electric school buses have no tailpipe emissions, they must be charged with 100% renewable electricity (wind, solar, hydro) to be truly zero emissions. Otherwise, their emissions reflect the local electric generating resource supplies from the grid. The national average electricity generating sources are burning natural gas (38%), coal (22%), nuclear (22%), and renewables (20%). The climate and clean air benefits of all-electric vehicles, including school bus fleets, will only be realized when the nation has an electric supply that is based fully on all renewable sources.

    The driving range of electric buses is a concern for some rural school districts that operate in colder areas, where using heaters cuts into useful driving range. One solution is to add more buses to cover the service shortfall from electric buses. But, recently 86% of school bus districts across the country reported that, because of COVID-19 and other factors, they’re struggling to hire drivers. If they can’t cover their trimmed down or basic routes, expanding service isn’t an option.

    Electrified school buses heavily subsidized with government funding (as much as $375,000 for one electric bus and up to $20,000 for charging infrastructure assistance) will no doubt turn out to be good choices for some school bus operators, particularly those that have the means to support significant and essential investments in charging infrastructure. But it will require many considerations.

    For example, unattended remote school bus staging yards where drivers pick up their buses may have to be relocated or equipped with new charging infrastructure and other supporting infrastructure like fencing and/or security systems. For private and contracted school bus service providers, the new fueling requirements, limited ranges, and lack of charging infrastructure for electrified buses present new issues to evaluate in serving their private charter businesses. For example, some bus charter trips can occur overnight or well outside the typical driving range served for local school bus service areas. It would be challenging to use electric school buses for charter services because they require specialized charging infrastructure. So drivers would be required to factor in new complexities to the trip such as changes to the route and the time needed to accommodate the vehicle’s fueling needs.

    It's hard to know exactly how many diesel buses might be replaced with alternative fuels under the new school bus program. According to the Environmental Protection Agency’s funding allocation plan, with the cost at nearly $400,000 for a single full size electric bus and charging infrastructure, the first round of $500 million has the potential to fund about 1,250 buses, somewhat more with smaller buses and other options. Given that, it’s safe to say that with a population of half a million buses, diesel technology will continue to provide reliable, safe, and efficient service to the majority of the nation’s school bus-riding children for many years to come.

    School districts denied funding in this program still have other options they can pursue on their own, or through other assistance programs. Replacing the oldest diesel buses with the new generation buses can reduce emissions and improve fuel efficiency, as well as all the safety advantages of new buses. Because these are far lower cost than other alternatives, many more buses can be upgraded and many more children have the potential to benefit.

    Others will be inspired to consider using advanced renewable and biodiesel fuels, either in blends or fully in place of conventional diesel fuel to reduce their greenhouse gas and other emissions. The advantage here is that this can be accomplished now, without any new fueling infrastructure or the need to acquire new buses. The result is zero new infrastructure or vehicle expenses and up to 86% fewer emissions literally overnight. This spreads the climate, clean air, and economic benefits much further, reaching more buses and enabling more schools and students to contribute to reducing emissions for the greater good. Now that’s a powerful lesson in using resources wisely to start this school year.

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