Comparative Study of Regulated and Unregulated Air Pollutant Emissions before and after Conversion of Automobiles from Gasoline Power to Liquefied Petroleum Gas/Gasoline Dual-Fuel Retrofits

Abstract

Liquefied petroleum gas (LPG) is increasingly being examined as an alternative to gasoline use in automobiles as interest grows in reducing air pollutant emissions. In this study, emissions of regulated (CO, THC, NO(x)) and unregulated air pollutants, including CO2, particulate matter (PM), polycyclic aromatic hydrocarbons (PAHs), and BTEX (acronym for benzene, toluene, ethylbenzene, xylene), were measured before and after conversion of nine gasoline-powered automobiles to LPG/ gasoline dual-fuel retrofits. The tests were conducted on a standard chassis dynamometer in accordance with the United States Environmental Protection Agency FTP-75 test procedure, with the exception that all tests were conducted under hot-start driving conditions. The influences of LPG on air pollutant emission levels and carcinogenic potency were investigated and compared with gasoline. The results showed average emission factors of 0.14 g/km, 0.33 mg/km, 0.09 g/km, 0.44 g/km, and 197 g/km for CO, THC, NO(x), PM, and CO2, respectively, for LPG/ gasoline dual-fuel retrofits. Paired-sample t-test results indicated that the emissions of CO (p = 0.03), THC (p = 0.04), and CO2 (p = 4.6 x 10(-8)) were significantly reduced with the retrofit in comparison with gasoline-powered automobiles. The reduction percentages were 71%, 89%, and 14% for CO, THC, and CO2, respectively. The average total PAH emission factor for LPG was 217 microg/km, which is significantly lower than gasoline (863 microg/km; p = 0.05). The PAH corresponding carcinogenicities (BaP(eq)) were calculated via toxic equivalencies based on benzo(a)pyrene (BaP). Paired-sample t-test results fortotal BaP(eq) emissions showed no significant difference between gasoline (30.0 microg/km) and LPG (24.8 microg/km) at a confidence level of 95%. The discrepancy between PAH and BaP(eq) emissions resulted from the higher emission percentages of high molecular weight PAHs for LPG, which might be from lubricant oil. The average emission factors of benzene, toluene, ethylbenzene, and xylene were 351, 4400, 324, and 1100 microg/ km, respectively, with LPG as fuel, which were all significantly lower than those for gasoline (95% confidence level). The average reduction percentages were 78%, 61%, 57%, and 58% for benzene, toluene, ethylbenzene, and xylene, respectively.

Observation of increases in emission from modern vehicles over time in Hong Kong using remote sensing

“…The differences between emissions of vehicles operating on different fuels are likely due to operating characteristics of different engines-petrol and LPG engines typically operate at rich conditions, under which CO and HC emissions are increased and NO emission is decreased, while diesel engines typically operate at lean conditions, under which higher level of NO and lower levels of CO and HC are emitted (Ceviz and Yüksel, 2005). Result showing that petrol vehicles emit less NO than LPG vehicles agrees with previous work (Ceviz and Yüksel, 2005;Yang et al, 2007).…”

“…However, results showing that LPG taxis emitting higher levels of HC compared to petrol passenger cars are opposite of the conclusion found in previous work (Ning and Chan, 2007;Yang et al, 2007). LPG vehicles having high emissions may be a result of their high mileage- Table 5 shows that, on average, a LPG vehicle travelled 110,000km per year, compared to 11,500km for a petrol vehicle and 33,000km for a diesel vehicle.…”

“…Thus remote sensing enables examination of emission factors of vehicles with different model years. In many cities, Liquified Petroleum Gas (LPG) vehicles have been introduced to reduce fleet emissions (Ning and Chan, 2007;Yang et al, 2007). By comparing on-road emissions of LPG vehicles and vehicles fuelled by conventional fuels operating under similar conditions, the effectiveness of alternatively-fuelled vehicles in reducing vehicle emissions can be examined.…”

On-board measurement of emissions from liquefied petroleum gas, gasoline and diesel powered passenger cars in Algeria

“…On-board measurement of emissions from liquefied petroleum gas, gasoline and diesel powered passenger cars in Algeria Only a few measurements with LPG-powered vehicles have been performed on-board to evaluate pollutant emissions under real driving conditions. A vehicle fuel switch from gasoline to LPG was found to decrease CO 2 emissions measured on a chassis dynamometer by 14% (Ristovski, 2005;Yang, 2007), and carbon monoxide (CO) and total hydrocarbons (THC) by 71% and 89%, respectively. Using the remote sensing technique, Ning and Chan (2007) were able to measure and compare pollutant emissions for LPG, gasoline and diesel powered vehicles.…”

Levels, profiles and gas–particle distribution of atmospheric PCDD/Fs in vehicle parking lots of a South China metropolitan area

“…LPG is regarded as cleaner fuel than diesel or gasoline, emitting less greenhouse gases, particulate matters, ozone precursors, and polycyclic aromatic hydrocarbons (Chang et al, 2001;Ristovski et al, 2005;Lim et al, 2007;Yang et al, 2007;Adam et al, 2011), and is currently widely used in buses and taxies in China (Ou et al, 2010). About 5000 buses and 9300 taxies in Guangzhou were LPG-powered in 2005 and the numbers increased to 6430 and 16000 in 2006, respectively.…”