Date of Award


Document Type



Environmental Science

Thesis Advisor

Huiting Mao


This project investigated the chemical composition of exhaust emissions from buses with three types of engines and estimated annual emissions of key compounds including carbon dioxide (CO2), methane (CH4), ethyne (C2H2), ethane (C2H6), ethene (C2H4), propane (C3H8), and other volatile organic compounds (VOCs) from buses in the city of Syracuse. Exhaust samples were taken from one bus with a CNG ISL engine, one with a diesel ISL engine, and the final one with a C Gas plus engine in the idling, cruising, acceleration, and deceleration modes. The emissions were estimated both in kg per year and kg per km over three CENTRO bus routes that service the Syracuse University area. Carbon dioxide was the most dominant chemical in the exhaust emissions for all engines over all the routes, and the diesel engine produced the most out of the three engine types. The diesel engine had the highest CO2 mixing ratio with a value of 304,501 ppmv when cruising. That value is 295,879 ppmv above the next largest mixing ratio, which was emitted by the diesel engine when decelerating and was equal to 8,622 ppmv. The diesel created 2.27 x 109 kg CO2 for a single bus per year. The second most dominant chemical was methane. The C Gas Plus created the most CH4 with a cruising mode mixing ratio of 273 ppmv. It released 3.26 x 105 kg of methane per year. Of the VOCs, C3H8 had the highest mixing ratio for a given engine running mode in more cases than any of the others. Those cases were when the C Gas Plus was idling (7.0403 ppmv), the diesel was accelerating (11.497 ppmv), and when the C Gas Plus was cruising (8.7813 ppmv). Ethene produced by the C Gas Plus engine had the highest mixing ratio for deceleration (7.2748 ppmv). The CNG ISL produced 2.56 x 107 kg of emissions per year, the diesel created 2.27 x 109 kg/yr, and the C Gas Plus made 2.43 x 107 kg/yr.