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In 1993, the US Environmental Protection Agency (EPA) began to reduce urban residents' exposure to diesel exhaust from urban buses by implementing an urban bus retrofit/rebuild program. The program requires that when urban buses operating in metropolitan areas with populations over 750,000 are rebuilt, they are equipped with certified retrofit pollution control devices if available or are rebuilt with certified low emission components ( 1 ).
In March 2000, EPA initiated a voluntary diesel retrofit program that is the focus of this chapter. Several US states, amongst others California and NESCAUM (Northeast States for Coordinated Air Use Management) members, have launched additional and supporting activities. Emissions from heavy-duty diesel vehicles account for about 33% of all NOx emissions and 80% of all particulate emissions for instance in the densely populated northeastern states of the US ( 1 ). The emissions are increasing because the diesel fleet continues to grow and vehicle miles traveled increase. While in the long run significant reductions in heavy diesel pollution will be achieved through tightened diesel emission standards for 2004 and later model years, the in-use emissions of old vehicles have to be tackled because of their long lifetimes. Retrofit programs help to bridge the time gap until the new low-emission models have penetrated the fleets. Of all heavy-duty vehicles, urban buses circulate in the busiest and most densely populated urban areas and are therefore critical for achieving a healthy air quality.
Details about the strategies and measures taken, as well as the progress of the program, can be found on a special US EPA website ( w1 ). (Additional information is provided in ( w2 ) and ( w3 )). The program is designed to help fleet owners and operators as well as air quality planners to take advantage of the technical possibilities to reduce diesel emissions especially from large fleets. Retrofit manufacturers are involved as well; they contribute technical solutions in form of add-on devices or low emission parts of existing engines. State-owned laboratories are certifying the products. The program currently has retrofit activities in all major states of the Northeast, also for instance in Atlanta, Houston, San Diego, Los Angeles and Seattle ( w1 ). The program is directed towards heavy-duty engines in general, including buses, trucks and construction machinery. As of late-2002, all in all 70, 000 retrofits are either being installed or committed by the operators. EPA aims at reaching a number of 100,000 trucks, buses and construction vehicles.
The program has been launched on a national level, but is supported and implemented by EPA's regional offices ( w1 ). Some states have issued additional regulations and programs on their level; the association of Northeast States for Coordinated Air Use Management (NESCAUM) is particularly engaged in giving technical and scientific support, e.g. by developing certification criteria and guidelines. California has a number of programs that provide funding for retrofit measures either statewide or for specific countries (see ( 2 )). Funding opportunities and economic incentives are used within the policy frame set by EPA for air quality measures in general - they include emission trading, emission reduction credits, as well as tax and discount incentives (sales tax waivers, tax credits, discount purchases, cost share partnerships). Companies can receive tax credit incentives for purchasing pollution control equipment, implementing retrofit pollution prevention programs or hiring additional environmental staff. Tax and discount incentives are designed to encourage organizations to make investments that will reduce pollution ( w1 ).
The program aims at improvements in large fleets on a voluntary basis. (For more details see EPA presentations ( 3 ) ) The US EPA provides technical expertise and organizational support. It manages an informative website and motivates manufacturers of emission control equipment to actively participate in the efforts. The policy aims at bridging the time until new vehicle standards are enforced. The 2004 and 2007 standards will bring massive emission reductions and technological innovation for new vehicles coming into operation ( w1 ). The EPA first had announced a goal of 10,000 vehicles to be retrofitted but due to the positive public response, an ambitious new program aims at a total of 100,000 buses, trucks and off-road vehicles to be upgraded ( w3 ). The program raises public awareness, provides technical support and economic incentives for operators, initiates private sector research and investments, and supports existing air pollution control programs ( w1 ).
Retrofit technologies as defined here include engine renewal and engine upgrades, as well as after-market equipment with filters and catalysts. The EPA publishes a verified retrofit technology list. This list describes the technology, the percentage of expected emission reductions, and engine family compatibility ( w1 ). Considerations for eligible concepts have to include engine conditions, vehicle integration, low-sulfur fuel requirement, and maintenance.
Information about the use of available technologies in the various regional programs is given in ( 3 ). For further information on retrofit technologies, please visit the retrofit systems page.
Some retrofit projects require a shift to low sulfur fuels, preferably with sulfur content below 15 ppm. No serious difficulties or failures of the program have been published. The program has helped to bring a number of emission reduction products on the market. The Manufacturers of Emission Controls Association (MECA) has published a cost survey in December 2000, providing information about mean costs to users, as well as cost ranges, depending on engine size in terms of horsepower (hp) and yearly sales volume ( 3 ). For engine sizes of 201 to 300 hp and a yearly sales volume of 5,000, the following data are given:
- Oxidation catalysts - mean cost to user, including muffler replacement: US$ 1,400
- Diesel particulate filters - mean cost to user, including muffler replacement: US$ 4,500
- SCR cost to user range between US$ 13,000 and 35,000 ( 3 ).
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