This is the twenty-fifth in our series on the “ABCs of the AJP.”
The American Jobs Plan aims to electrify 20% of the country’s iconic yellow school bus fleet through a new “Clean Buses for Kids” program, alongside a broader effort to replace 50,000 diesel transit vehicles. The move will have important health benefits and assist in the electrification of the heavy duty transportation and freight sectors, which face additional challenges as they seek to decarbonize.
The benefits of reducing emissions from diesel engines, particularly from older models, are well-established. Diesel engines produce more oxides of nitrogen (“NOx” emissions) and more particulate matter (PM) than gasoline engines of comparable size. NOx is a precursor to ozone, which contributes to the formation of smog and acid rain, while PM is classified as a probable human carcinogen and does damage to the heart and lungs. Diesel engines also last for a very long time, sometimes even outliving the vehicle they were originally installed in. As a result, millions of decades-old diesel engines are still powering vehicles on the road, with NOx and PM emissions up to 20 to 40 times higher than what a new engine would produce. Studies have examined the air quality of diesel school buses specifically, and found children riding buses can experience PM concentrations that were sometimes 5-15 times higher than background ambient levels.
The AJP’s proposal to remove older, large (“heavy duty”) engines from commerce—like the ones that power school buses—is the latest in a series of initiatives to do the same. Congress has repeatedly authorized funds for this purpose, and diesel emission reduction projects have been a recurring component of settlements with auto manufacturers. California has also instituted a program requiring turnover of antiquated heavy duty fleets within the State.
When the President announced a Bipartisan Infrastructure Framework last week, he said the deal only includes $7.5 billion – or half – of the investments in electric buses he had originally proposed in the AJP. But that is more than the $0 for light-duty vehicle subsidies included in the bipartisan deal. This may reflect that heavy duty electrification presents a more difficult technical challenge than electrification of the country’s passenger car fleet, for which automakers have made the most aggressive commitments.
Fossil fuels are much more energy dense than current battery technology—whether gasoline or diesel fueled—meaning that a battery-powered vehicle must carry more weight in order to deliver the same amount of power or have the same range as one powered by an internal combustion engine. This poses a problem for the heavy duty sector, which generally must carry heavier loads over longer distances than passenger cars. School buses are appealing candidates for electrification in spite of these challenges, because they tend to drive regular, fixed routes over a limited geographic area, meaning that it is easier for them to refuel frequently without sacrificing needed function or drive time.
The hope of the Biden Administration is that, by incentivizing introduction of heavy duty electric vehicles in a sector where they are most viable, it will promote development of technology that can be used for more difficult use cases, like long-haul trucking. The effort will proceed alongside an initiative by EPA to further tighten emissions standards from these engines, in the wake of California’s decision to do the same last summer. The combined result should speed the phase down of antiquated sources of pollution disproportionately affecting the nation’s youth, and drive significant innovation in the heavy transportation sectors.