title: Unregulated greenhouse gas and ammonia emissions from current technology heavy-duty vehicles.
abstract: The study presents the measurement of carbonyl, BTEX (benzene, toluene, ethyl benzene, and xylene), ammonia, elemental/organic carbon (EC/OC), and greenhouse gas emissions from modern heavy-duty diesel and natural gas vehicles. Vehicles from different vocations that included goods movement, refuse trucks, and transit buses were tested on driving cycles representative of their duty cycle. The natural gas vehicle technologies included the stoichiometric engine platform equipped with a three-way catalyst and a diesel-like dual-fuel high-pressure direct-injection technology equipped with a diesel particulate filter (DPF) and a selective catalytic reduction (SCR). The diesel vehicles were equipped with a DPF and SCR. Results of the study show that the BTEX emissions were below detection limits for both diesel and natural gas vehicles, while carbonyl emissions were observed during cold start and low-temperature operations of the natural gas vehicles. Ammonia emissions of about 1 g/mile were observed from the stoichiometric natural gas vehicles equipped with TWC over all the driving cycles. The tailpipe GWP of the stoichiometric natural gas goods movement application was 7% lower than DPF and SCR equipped diesel. In the case of a refuse truck application the stoichiometric natural gas engine exhibited 22% lower GWP than a diesel vehicle. Tailpipe methane emissions contribute to less than 6% of the total GHG emissions.
  
  
  
  Modern heavy-duty diesel and natural gas engines are equipped with multiple after-treatment systems and complex control strategies aimed at meeting both the performance standards for the end user and meeting stringent U.S. Environmental Protection Agency (EPA) emissions regulation. Compared to older technology diesel and natural gas engines, modern engines and after-treatment technology have reduced unregulated emissions to levels close to detection limits. However, brief periods of inefficiencies related to low exhaust thermal energy have been shown to increase both carbonyl and nitrous oxide emissions.
authors.affiliation: a Mechanical and Aerospace Department , West Virginia University , Morgantown , WV , USA.
authors.forename: Arvind
authors.initials: A
authors.lastname: Thiruvengadam
authors.affiliation: a Mechanical and Aerospace Department , West Virginia University , Morgantown , WV , USA.
authors.forename: Marc
authors.initials: M
authors.lastname: Besch
authors.affiliation: a Mechanical and Aerospace Department , West Virginia University , Morgantown , WV , USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Carder
authors.affiliation: c South Coast Air Quality Management District, Diamond Bar , CA , USA.
authors.forename: Adewale
authors.initials: A
authors.lastname: Oshinuga
authors.affiliation: c South Coast Air Quality Management District, Diamond Bar , CA , USA.
authors.forename: Randall
authors.initials: R
authors.lastname: Pasek
authors.affiliation: c South Coast Air Quality Management District, Diamond Bar , CA , USA.
authors.forename: Henry
authors.initials: H
authors.lastname: Hogo
authors.affiliation: b University of Nevada , Reno , NV , USA.
authors.forename: Mridul
authors.initials: M
authors.lastname: Gautam
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000641:Ammonia / Q000032:analysis*; D005740:Gases / Q000032:analysis; D005742:Gasoline / Q000032:analysis; D017752:Greenhouse Effect; D018986:Motor Vehicles; D059206:Natural Gas / Q000032:analysis; D014481:United States; D014484:United States Environmental Protection Agency / Q000592:standards; D001335:Vehicle Emissions / Q000032:analysis*
chemical_list: D000393:Air Pollutants; D005740:Gases; D005742:Gasoline; D059206:Natural Gas; D001335:Vehicle Emissions; D000641:Ammonia