Bus Filters Remove Tons of Soot From Bay Area Air

Bay Area residents can expect the region’s normally excellent air quality to become even better in the years ahead, as the Metropolitan Transportation Commission (MTC), the Bay Area Air Quality Management District and the area’s transit systems near completion of an unprecedented diesel cleanup program.

San Francisco Muni bus displaying the Clean Diesel Bus Program sign Photo by Peter Beeler, MTC

By John Goodwin
Published: October, 2006

The involved agencies gathered in late September at Treasure Island to announce the approach of the project’s completion. The featured speaker was San Francisco Mayor Gavin Newson, who reported that San Francisco Muni has retrofitted all 424 of its targeted diesel buses.

Newsom framed the Bay Area’s Clean Diesel Bus Program as part of the region’s contribution to a larger worldwide effort.  We’ve got an obligation to deal with the realities of our emissions, with our fleet of buses, vehicles and other polluting sources, to turn the tide of global warming, he said.

Through the Clean Diesel Bus Program, more than 1,700 diesel buses from 13 Bay Area transit districts are being retrofitted with diesel exhaust filters. Combined, these high-tech emission control filters annually will capture more than 50 tons of harmful particulate matter and 400 tons of oxides of nitrogen (NOx) that otherwise would have been emitted by buses into Bay Area air.

Diesel particulate matter is a toxic air contaminant that can cause lung disease and cancer. Oxides of nitrogen (NOx), another component of diesel exhaust, are a precursor to ozone, which can cause respiratory disease, according to the California Air Resources Board.

The Air District, MTC and the region’s transit districts provided funding for implementation of the clean diesel bus program. Installation of the devices, which are manufactured by San Leandro-based Cleaire Advanced Emission Controls, began in 2003. Nearly 1,400 exhaust filters for Bay Area buses already have been delivered. Most of the remaining exhaust filters are scheduled for installation by mid-2007.

The Air District is committed to achieving clean air to protect the public’s health and the environment, said Jack Broadbent, executive officer of the Bay Area Air Quality Management District. Technology can play an important role in reducing emissions from mobile sources and help the Bay Area to attain and maintain air quality standards. This project represents a step towards reducing emissions from buses in our region.

While the 13 Bay Area transit districts participating in the bus retrofit have purchased some clean new buses, most of the exhaust reduction is coming from the installation of diesel exhaust filters on existing buses that have years of life remaining. The devices capture 85 percent of the particulate matter and reduce 25 percent of the NOx created by the buses’ engines. Each installation costs about $18,000, compared to $140,000 or more, for a new bus.

The installation of the exhaust filters goes a long way to improving air quality, said Steve Heminger, executive director of MTC. Retrofitting buses is a cost-effective way to clean our air.

On an average Bay Area bus, each diesel exhaust filter reduces particulate matter emissions by 59 pounds per year and reduces NOx emissions by 515 pounds per year. We are proud to play a role in removing diesel soot from Bay Area air, said Kevin Shanahan, president of Cleaire. This is a program and a practical solution that really works.
San Francisco Muni is leading the way for the Bay Area by retrofitting 424 of its diesel buses. AC Transit will have 416 diesel exhaust filters when its retrofit program is complete in December 2006.

San Francisco’s Mayor, Gavin Newsom, performs a “white handkerchief” test to show the crowd how effective the Cleaire diesel exhaust filters are. Photos by: Peter Beeler, MTC