Climate and Health Relevant Emissions from in-Use Indian Three-Wheelers Fueled by Natural Gas and Gasoline

Abstract

Auto-rickshaws in India use different fuels and engine technologies, with varying emissions and implications for air quality and climate change. Chassis dynamometer emission testing was conducted on 30 in-use auto-rickshaws to quantify the impact of switching from gasoline to compressed natural gas (CNG) in spark-ignition engines. Thirteen test vehicles had two-stroke CNG engines (CNG-2S) and 17 had four-stroke CNG engines (CNG-4S), of which 11 were dual-fuel and operable on a back-up gasoline (petrol) system (PET-4S). Fuel-based emission factors were determined for gaseous pollutants (CO(2), CH(4), NO(X), THC, and CO) and fine particulate matter (PM(2.5)). Intervehicle variability was high, and for most pollutants there was no significant difference (95% confidence level) between "old" (1998-2001) and "new" (2007-2009) age-groups within a given fuel-technology class. Mean fuel-based PM(2.5) emission factor (mean (95% confidence interval)) for CNG-2S (14.2 g kg(-1) (6.2-26.7)) was almost 30 times higher than for CNG-4S (0.5 g kg(-1) (0.3-0.9)) and 12 times higher than for PET-4S (1.2 g kg(-1) (0.8-1.7)). Global warming commitment associated with emissions from CNG-2S was more than twice that from CNG-4S or PET-4S, due mostly to CH(4) emissions. Comprehensive measurements and data should drive policy interventions rather than assumptions about the impacts of clean fuels.

Carbon Nanotube and Fullerene Emissions from Spark-Ignited Engines

“…Details of the vehicles, engines, and emissions testing protocol can be found in Reynolds, Grieshop, et al (2011). A subset of the 4-stroke vehicles was equipped with back-up gasoline fuel systems and was also tested operating on gasoline.…”

“…Vehicles were tested with the lubrication oil and state of tuning as received to reflect in-use conditions. Further details on sampling methods and vehicle recruitment are published in a related paper (Reynolds, Grieshop, et al 2011) and emissions for the thirty-vehicle set are summarized in Online Supplemental Information (OSI) Part A.…”

“…For each vehicle tested, fuel-based emission factors were determined for gaseous pollutants, PM 2.5 , OC, and EC (Reynolds, Grieshop, et al 2011). Table 1 gives emission factors for the subselection of vehicles for which TPS/TEM sampling and analysis were conducted.…”

“…This assumption can be partially tested by using time-resolved measurements of PM 2.5 , CO 2 , CO, and hydrocarbons to estimate the PM emissions (per unit of fuel) for the acceleration portion of the IDC and the full IDC (Reynolds, Grieshop, et al 2011). These indicate that the ratio of the PM emissions (acceleration/ full IDC) is 1.08 ± 0.4.…”

“…Most autorickshaws use SI engines and many are also capable of running on gasoline, which offered an opportunity to test them in both fueling modes. IARP was designed to assess fuel switching and technology policy options and is described elsewhere (Reynolds, Grieshop, et al 2011;. Here, we focus on the results from sampling PM and characterizing nonvolatile particle morphology.…”