Diesel Vehicle Emission Estimates from Bangkok and Thailand

Abstract:

Diesel vehicles are major emitters of particulate matter and other pollutants. Due to emission differences between in-use and new diesel vehicles, it is difficult to estimate real world contribution using new vehicle data or standards. However, such estimates are needed not only for urban air quality models, but for large regional and global models that simulate long-range pollutant transport and global impacts. In this study, we explore methods for estimating diesel emissions by combining measured data with information about driving modes and speeds and vehicle fleet information. We also report chemical composition of the emitted particulate matter.

We rely on emission data from the DIESEL project implemented by the World Bank. In-use cars, vans, buses, and trucks were tested for hydrocarbons, nitrogen oxides, carbon monoxide, carbon dioxide and particulate matter emission. We combine these real-time data with information about driving conditions and high emitters to estimate emissions from Bangkok and Thailand. We classified the real-time data into travel modes (acceleration, deceleration, and cruising). At every speed, deceleration mode generated more emission for light duty while acceleration mode emitted more for heavy duty. Some of the important factors include high emissions per distance at lower speeds (<10 km/hr), reduction in emissions for newer vehicles, and the contribution of high emitters.

In 2006, we estimate that particulate matter, hydrocarbon, oxide of nitrogen, carbon monoxide, and carbon dioxide emitted by diesel vehicles totaled 17, 18, 174, 120 ktons, and 18 Mtons, respectively. We present an extrapolation of our emission estimate to the country of Thailand and discuss the uncertainties inherent in such an extrapolation. We also compare the more detailed method based on driving conditions with an emission estimate based on fuel mass, and demonstrate that fuel-based emission factors are a reasonable method of estimating emissions for regional inventories.

Keywords: diesel vehicles, emission factors, emission estimation