Natural gas vehicles have proved to be an economic alternative to meet US EPA emissions regulation. In particular the 3-way oxidation catalyst equipped, 2010 emissions compliant stoichiometric heavy-duty natural gas engines have proven to be a viable alternative in comparison to SCR equipped heavy-duty diesel engines. Stoichiometric natural gas engine technology is capable of meeting the stringent PM and NOx standards with only a 3-way oxidation catalyst as its exhaust after-treatment system. However, lack of sufficient data and literature on the exhaust emissions from advanced natural gas engines and the potential adverse health effects has raised concern amongst regulatory agencies.
This CARB funded study focuses primarily on characterizing the toxicity of the volatile fraction of PM from advanced heavy-duty natural gas engines. The objective of the study also includes characterizing the unregulated species of the exhaust together with number concentration and size distribution of ultrafine nanoparticle emissions. The work plan involved the chassis dynamometer testing of two heavy-duty natural gas transit buses that are compliant with the US EPA 2010 emissions regulation. Since the project was focused at investigating the effect of volatility on toxicity, the test procedure included a thermal denuder to remove the volatile component prior to collection on the filters.
ARB is conducting toxicity related assays of samples collected in this test program, and will provide those data as an addendum to this report.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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