Buses account for a high percentage of U.S. emissions, prompting an industry-wide push to reduce pollutant output. Alternatives such as natural gas and even gasoline hybrids are getting increased attention as regulators and vehicle owners try to balance conservation and cost.
At the recent BusCon convention in Chicago, panelists focused on 2010 engine emissions while also looking beyond them to see how engines can continue to evolve and improve the environment. Regulations now in place are expected to make an enormous impact.
“Emissions nationwide would have crept up to 3 million tons of NOx per year by 2030 without new standards,” said Francisco Acevedo, Program Manager for the U.S. EPA. “They are under 500,000 tons because of the new standards.”
The 2030 date is critical for EPA planning. That is when older, dirtier engines will have pretty much disappeared, leaving only newer, cleaner diesel engines.
Those improvements will come in large part from upgrades in truck and bus engines. Acevedo noted that trucks and buses comprise 28% of the NOx and 20% of the particulate matter emissions in the U.S.
Engine design will play a significant role in these improvements. But changes in fuel will have a critical role in the race to improve air quality. Cleaner diesel fuel is already being transformed to meet tighter regulations.
Diesel fuel for highway vehicles must drop to a sulfur level of 15 ppm next year. By 2012, all diesel fuel will be at 15 ppm, Acevedo said.
Panelists at BusCon also predicted that an increasing number of buses may make the transition to natural gas. It offers a number of clean air benefits while also reducing America’s reliance on imported fuel.
“Natural gas has lower emissions, and it can be renewable with landfills and bio technologies,” said William Boyce, Marketing Manager for Cummins Westport Inc. “There’s an abundant supply in North America; if we put 10 million natural gas vehicles on the road, we would use only 3% of our supply.”
It is not expensive to convert diesels to natural gas, since around 80% of the engine parts are the same. The costs of fuel are also low, from 35 to 50% less than diesel fuel. In a wells-to-wheels analysis, it can be 20 to 25% less than diesel. If natural gas comes from landfills, that soars to 75%, Boyce said.
While diesel providers push to reduce emissions, proponents of gasoline engines are striving to move into markets that have traditionally gone to diesel. Some developers feel that gasoline hybrids can help gasoline displace diesel.
“Gasoline hybrids make sense because they have simple exhaust aftertreatment and leverage the billions in investments for cars,” said Michael Hennessy, Regional Sales Manager for ISE Corp., which makes gasoline hybrids. “The aftertreatment component for gasoline is reduced to a catalytic converter. With diesel there are far more components in aftertreatment systems.”
The cost of a 2010-compliant diesel aftertreatment system will be $11,000 or higher, compared to around $1200 for a gasoline engine’s catalytic converter. He also noted that diesel output must be derated when the particulate filter is being regenerated.