Emissions Comparisons from Alternative Fuel Buses and Diesel Buses with a Chassis Dynamometer Testing Facility

Wang, Wen G.; Clark, Nigel N.; Lyons, Donald W.; Yang, Rong; Gautam, Mridul; Bata, Reda M.; Loth, John L.

doi:10.1021/es9701063

Cited by 100 publications

(50 citation statements)

References 6 publications

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“…Figure 7A illustrates this, showing that particulate mass emissions (g/mile) in NTDE from transit buses tested with the Central Business District cycle are more comparable to the emission levels from CNG-fueled transit buses than from TDE buses. 47,[93][94][95][96][97][98][99][100] Figure 7B shows that for particulate mass emissions (g/mile) in passenger cars, NTDE emission levels are more comparable to gasoline-and CNG-fueled vehicles. 76,101,102 In summary, the transit bus and passenger car data show that NTDE mass particulate emissions are 20-70 times lower than those for TDE, and are in the range, if not lower than, particulate mass emission levels reported for CNG-and gasoline-fueled vehicles.…”

Section: Discussionmentioning

confidence: 99%

Particulate Matter in New Technology Diesel Exhaust (NTDE) is Quantitatively and Qualitatively Very Different from that Found in Traditional Diesel Exhaust (TDE)

Hesterberg

Long

Sax

et al. 2011

Journal of the Air & Waste Management Association

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Diesel exhaust (DE) characteristic of pre-1988 engines is classified as a "probable" human carcinogen (Group 2A) by the International Agency for Research on Cancer (IARC), and the U.S. Environmental Protection Agency has classified DE as "likely to be carcinogenic to humans." These classifications were based on the large body of health effect studies conducted on DE over the past 30 or so years. However, increasingly stringent U.S. emissions standards for particulate matter (PM) and nitrogen oxides (NO x ) in diesel exhaust have helped stimulate major technological advances in diesel engine technology and diesel fuel/lubricant composition, resulting in the emergence of what has been termed New Technology Diesel Exhaust, or NTDE. NTDE is defined as DE from post-2006 and older retrofit diesel engines that incorporate a variety of technological advancements, including electronic controls, ultra-low-sulfur diesel fuel, oxidation catalysts, and wall-flow diesel particulate filters (DPFs). As discussed in a prior review (T. W. Environ. Sci. Technol. 2008, 42, 6437-6445), numerous emissions characterization studies have demonstrated marked differences in regulated and unregulated emissions between NTDE and "traditional diesel exhaust" (TDE) from pre-1988 diesel engines. Now there exist even more data demonstrating significant chemical and physical distinctions between the diesel exhaust particulate (DEP) in NTDE versus DEP from pre-2007 diesel technology, and its greater resemblance to particulate emissions from compressed natural gas (CNG) or gasoline engines. Furthermore, preliminary toxicological data suggest that the changes to the physical and chemical composition of NTDE lead to differences in biological responses between NTDE versus TDE exposure. Ongoing studies are expected to address some of the remaining data gaps in the understanding of possible NTDE health effects, but there is now sufficient evidence to conclude that health effects studies of pre-2007 DE likely have little relevance in assessing the potential health risks of NTDE exposures. INTRODUCTIONDiesel-engine exhaust (DE) exposures and health effects have been studied extensively for decades. DE is a source of particulate matter (PM), nitrogen oxides (NO x ), carbon monoxide (CO), and a number of air toxics (e.g., aldehydes,

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Section: Discussionmentioning

confidence: 99%

Particulate Matter in New Technology Diesel Exhaust (NTDE) is Quantitatively and Qualitatively Very Different from that Found in Traditional Diesel Exhaust (TDE)

Hesterberg

Long

Sax

et al. 2011

Journal of the Air & Waste Management Association

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“…Alternative ways of measuring particle emissions from vehicles are at the kerbside, often giving values for the average fleet, or by chassis dynamometer, measuring vehicles individually (e.g. Janhall et al, 2004;Wang et al, 1997;BanWeiss et al, 2010). However, in the latter case it is difficult, if not impossible, to accurately mimic the real-world dilution.…”

Section: å M Hallquist Et Al: Particle and Gaseous Emissions Fmentioning

confidence: 99%

“…In the literature there are some studies that have compared the particle emissions from diesel-fuelled and CNG-fuelled buses (Jayaratne et al, , 2009Wang et al, 1997;Ullman et al, 2003;Lanni et al, 2003;Norman et al, 2002;Clark et al, 1999). This study takes these investigations further by determining both gaseous (NO x , CO and HC) and size-resolved particle emission factors for CNG and diesel buses belonging to different Euro classes with various aftertreatment equipment, i.e.…”

Section: å M Hallquist Et Al: Particle and Gaseous Emissions Fmentioning

confidence: 99%

Particle and gaseous emissions from individual diesel and CNG buses

et al. 2013

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In this study size-resolved particle and gaseous emissions from 28 individual diesel-fuelled and 7 compressed natural gas (CNG)-fuelled buses, selected from an in-use bus fleet, were characterised for real-world dilution scenarios. The method used was based on using CO₂ as a tracer of exhaust gas dilution. The particles were sampled by using an extractive sampling method and analysed with high time resolution instrumentation EEPS (10 Hz) and CO₂ with a non-dispersive infrared gas analyser (LI-840, LI-COR Inc. 1 Hz). The gaseous constituents (CO, HC and NO) were measured by using a remote sensing device (AccuScan RSD 3000, Environmental System Products Inc.). Nitrogen oxides, NO_x, were estimated from NO by using default NO₂/NO_x ratios from the road vehicle emission model HBEFA3.1. The buses studied were diesel-fuelled Euro III–V and CNG-fuelled Enhanced Environmentally Friendly Vehicles (EEVs) with different after-treatment, including selective catalytic reduction (SCR), exhaust gas recirculation (EGR) and with and without diesel particulate filter (DPF). The primary driving mode applied in this study was accelerating mode. However, regarding the particle emissions also a constant speed mode was analysed. The investigated CNG buses emitted on average a higher number of particles but less mass compared to the diesel-fuelled buses. Emission factors for number of particles (EF_PN) were EF_{PN, DPF} = 4.4 ± 3.5 × 10¹⁴, EF_{PN, no DPF} = 2.1 ± 1.0 × 10¹⁵ and EF_{PN, CNG} = 7.8 ± 5.7 ×10¹⁵ kg fuel⁻¹. In the accelerating mode, size-resolved emission factors (EFs) showed unimodal number size distributions with peak diameters of 70–90 nm and 10 nm for diesel and CNG buses, respectively. For the constant speed mode, bimodal average number size distributions were obtained for the diesel buses with peak modes of ~10 nm and ~60 nm. Emission factors for NO_x expressed as NO₂ equivalents for the diesel buses were on average 27 ± 7 g (kg fuel)⁻¹ and for the CNG buses 41 ± 26 g (kg fuel)⁻¹. An anti-relationship between EF_{NO_x} and EF_PM was observed especially for buses with no DPF, and there was a positive relationship between EF_PM and EF_CO

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“…As a result, CNG is expected to produce less particulate matter emissions than diesel. A number of studies have reported that hydrocarbon (HC), carbon monoxide (CO), and particulate matter (PM) emissions from CNG buses are lower or comparable to diesel buses and trucks certified to comparable emission standards (Crawford et al, 2010;Turrio-Baldassarri et al, 2006;Ayala et al, 2002Ayala et al, , 2003, while relatively high oxides of nitrogen (NO X ) emissions from CNG buses with lean combustion were a concern (Wang et al, 1997;Sigal, 2000). To address the concern of NO X emissions from CNG buses and to meet tighter engine emission standards, manufacturers of CNG engines have developed improved engine and exhaust control technologies.…”

Section: Introductionmentioning

confidence: 99%

Criteria pollutant and greenhouse gas emissions from CNG transit buses equipped with three-way catalysts compared to lean-burn engines and oxidation catalyst technologies

Yoon

Collins

Thiruvengadam

et al. 2013

Journal of the Air & Waste Management Association

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Engine and exhaust control technologies applied to compressed natural gas (CNG) transit buses have advanced from lean-burn, to lean-burn with oxidation catalyst (OxC), to stoichiometric combustion with three-way catalyst (TWC). With this technology advancement, regulated gaseous and particulate matter emissions have been significantly reduced. Two CNG transit buses equipped with stoichiometric combustion engines and TWCs were tested on a chassis dynamometer, and their emissions were measured. Emissions from the stoichiometric engines with TWCs were then compared to the emissions from lean-burn CNG transit buses tested in previous studies. Stoichiometric combustion with TWC was effective in reducing emissions of oxides of nitrogen (NO X ), particulate matter (PM), and nonmethane hydrocarbon (NMHC) by 87% to 98% depending on pollutants and test cycles, compared to lean combustion. The high removal efficiencies exceeded the emission reduction required from the certification standards, especially for NO X and PM. While the certification standards require 95% and 90% reductions for NO X and PM, respectively, from the engine model years 1998-2003 to the engine model year 2007, the measured NO X and PM emissions show 96% and 95% reductions, respectively, from the lean-burn engines to the stoichiometric engines with TWC over the transient Urban Dynamometer Driving Schedule (UDDS) cycle. One drawback of stoichiometric combustion with TWC is that this technology produces higher carbon monoxide (CO) emissions than lean combustion. In regard to controlling CO emissions, lean combustion with OxC is more effective than stoichiometric combustion. Stoichiometric combustion with TWC produced higher greenhouse gas (GHG) emissions including carbon dioxide (CO 2 ) and methane (CH 4 ) than lean combustion during the UDDS cycle, but lower GHG emissions during the steady-state cruise cycle.Implications: Stoichiometric combustion with three-way catalyst is currently the best emission control technology available for compressed natural gas (CNG) transit buses to meet the stringent U.S. Environmental Protection Agency (EPA) 2010 heavy-duty engine NO X emissions standard. For existing lean-burn CNG transit buses in the fleet, oxidation catalyst would be the most effective retrofit technology for the control of NMHC and CO emissions.

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Emissions Comparisons from Alternative Fuel Buses and Diesel Buses with a Chassis Dynamometer Testing Facility

Cited by 100 publications

References 6 publications

Particulate Matter in New Technology Diesel Exhaust (NTDE) is Quantitatively and Qualitatively Very Different from that Found in Traditional Diesel Exhaust (TDE)

Particulate Matter in New Technology Diesel Exhaust (NTDE) is Quantitatively and Qualitatively Very Different from that Found in Traditional Diesel Exhaust (TDE)

Particle and gaseous emissions from individual diesel and CNG buses

Criteria pollutant and greenhouse gas emissions from CNG transit buses equipped with three-way catalysts compared to lean-burn engines and oxidation catalyst technologies

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