The ongoing difficulties in reducing diesel engine emissions
sustainably has been highlighted with the recall of approximately 1250
urban bus engines in the US for emissions based repairs. The engines
have experienced several problems, including particulate filter
plugging and turbocharger defects.
The US Environmental Protection Agency (EPA) discovered the bus engine
problem and its scope through transit bus fleet manager complaints,
emission related defect reports, and through discussions with the
engine manufacturer. After the manufacturer performed a series of
tests on the improved particulate filters and filed completed emission
related defect reports, EPA agreed to a recall campaign by the
manufacturer. The recall affects States outside of California, where
the problem will be managed separately by the California Air Resources
Board.
With higher emissions standards being introduced progressively in the
US and elsewhere, manufacturers are expected to face increasing
difficulty in meeting the tougher standards or sustaining the standards
once the vehicles become operational. Even with expensive emissions
treatments in place, the long-term viability of the treatments is
questionable. The EPA monitoring regime is designed to ensure that
vehicles do not fall below the accepted standards while in service.
Natural gas powered engines, which consistently outperform diesel
engines on emissions performance, are already meeting US EPA 2010
standards. A recent TIAX study concluded that increased costs and
reduced efficiencies through emissions compliance of diesel engines
will make natural gas engines more economically viable than diesel in
coming years (see NGV Global story here)
Details of the engine recall can be found here.
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