Emission Testing Services

EPA-MEXICO CITY DIESEL RETROFIT PILOT PROJECT

Client: Centro de Transporte Sustentable, Mexico City

The U.S. Environmental Protection Agency and the Government of Mexico City carried out a cooperative project to demonstrate the effectiveness of diesel exhaust retrofit systems in transit buses in Mexico City. The Centro de Transporte Sustentable (CTS) was the prime contractor for the demonstration program. Emission measurements to were performed by a team comprising Ambientalis (a Mexican air quality consulting firm) and EF&EE. Ambientalis personnel carried out the day-to-day emission testing, while EF&EE provided training and technical support for the emission testing, data quality control, and data analysis.

A total of 15 buses were tested: eight 1991 Mercedes, six 2002 Internationals, and two 2002 Mercedes. The 2002 buses were certified to U.S. 1998 emission standards, and were retrofitted with diesel particulate filters. The 1991 Mercedes buses had been subject to smoke standards only when originally manufactured, and were retrofit with diesel oxidation catalysts. All buses were operated on ultra-low sulfur diesel fuel for the duration of the program.

All emission tests were performed using the RAVEM system belonging to the Government of Mexico City. Pollutants measured included PM, NOx, CO, and CO2. The test routes included to actual bus routes, and one artificial route performed entirely within the bus service base. Emission measurements were performed shortly before installation of the retrofit controls, shortly after installation, and again after approximately nine months of operation. Some buses were also retested after the retrofit systems were removed.

The test results showed that the U.S. 1998 emission standards were highly effective in reducing bus emissions: the 2002 vehicles averaged 0.15 to 0.27 grams per kilometer of PM, compared to 1.7 to 2.7 g/km for the 1991 buses. The DPFs reduced the already-low PM emissions from the 2002 buses by another 86 to 92%, while the diesel oxidation catalysts were only about 22% effective.