While the pollution control equipment is not required, the department said it is demonstrating "national leadership" by working voluntarily to reduce particulate emissions by up to 90% from a portion of the city’s sanitation truck fleet.
The department said plans to retrofit about 260 sanitation trucks over the next three years with diesel particulate filters, and has acquired four compressed natural gas street sweepers with the financial assistance of the project participants.
“In deploying these vehicles, we have reached a milestone of the project: the department is currently pilot testing four refuse collection trucks in order to determine the direction the project takes over the next several years," said Jerry Della Corte, deputy commissioner of support operations for the department. "This will provide a template for early reduction of sanitation vehicle emissions across the country.”
This project is one of only a few such retrofit programs in the country. While diesel particulate filters are commercially viable for higher exhaust temperature applications such as on urban buses, the technology is still evolving for low exhaust temperature applications such as on sanitation vehicles.
In the colder northeast climate, sanitation trucks normally do not exhibit exhaust temperatures conducive to passive filter regeneration. Without regeneration, particles continuously accumulate on the filter, which can lead to an increase in backpressure, potentially affecting engine performance and the engine itself.
“Because these filters are so efficient in removing particles from diesel exhaust, regeneration has become critical to their implementation in this project,” explained Christine Vujovich, vp of environmental policy at Cummins. “Our goal is to maximize the filter’s ability to regenerate while minimizing the risks involved in using the technology, primarily through the use of proprietary devices that will depower the engine upon sensing excessive backpressure.”
The Dept. of Sanitation will provide ultra low sulfur diesel fuel, a pilot project requirement. Sulfur in standard highway diesel fuel, averaging 350 ppm, reduces diesel particulate filter efficiency and increases filter regeneration temperature, thus making this technology less feasible on sanitation trucks. However levels of sulfur in diesel fuel, lower than 30 parts per million have virtually no effect on the filter catalyst.
Although EPA does not require the commercial availability of ultra low sulfur diesel fuel until 2006, Sprague Energy, the supplier of fuel for this project, has accelerated the commercial availability of ultra low sulfur diesel fuel in the Northeast due to interest in diesel particulate filter technology.
The first four trucks in a pilot test will undergo extensive performance and emissions testing and will be carefully monitored over the course of the winter. The program is testing two alternative filter technologies manufactured by Johnson Matthey Inc. and by Engelhard Corporation. Based on the performance, durability and emission testing of the filters, a single supplier will be chosen for the remaining program vehicles.
Fleetguard Nelson, a division of Cummins, designed and manufactured the project’s exhaust hardware including the filter assembly. The filters were installed at Cummins Metropower with engineering supervision provided by Cummins Inc. NESCAUM, a non-profit organization representing the eight Northeast states on air quality issues, is the project coordinator with technical guidance provided by Cummins Inc., the vehicles’ engine manufacturer, and M.J. Bradley & Associates, an environmental consulting firm in the advanced vehicle field.
“Although diesel filter technology will be required in the not too distant future, this project will demonstrate to fleet owners that it is available now in even difficult applications,” said Jason Grumet, executive director of NESCAUM.
The four CNG street sweepers, designed and custom built by the Johnston Sweeper Co. and deployed by the Dept. of Sanitation earlier this year, have lower exhaust emissions of particulate, NOx and VOC when compared to their diesel counterpart. These vehicles employ a ULEV rated CNG engine, manufactured by Cummins, and are equipped with oxidation catalysts to further reduce emissions. These new street sweepers will be evaluated for operation and emission reduction performance.
