California Urban Bus Standard (2002)
In February, 2000, the California ARB adopted a new regulation to reduce emissions of NOx and PM from urban transit buses. The rule includes a number of components that affect both engine manufacturers and bus fleet operators. Fleet operators have to choose between a “diesel path” and an “alternative fuel path” for their future bus procurements. The alternative fuel path requires that 85% of buses purchased or leased each year through model year 2015 are fueled by alternative fuels. Transit operators who stay on the diesel path can purchase diesel fueled buses, but are required to follow a more aggressive emission reduction schedule. When the regulation is fully implemented, buses on both paths will produce the same near-zero emission levels.
The regulation provides numerous detailed provisions and schedules, which can be summarized as follows:
• NOx fleet average of 4.8 g/bhp-hr begins in 2002 for both diesel and alternative fuel paths, which will require some transit agencies to retire their oldest, highest polluting buses.
• Ultra low sulfur diesel fuel (15 ppm wt.) is required beginning July 1, 2002.
• All pre-2004 diesel buses have to be retrofitted with ARB-certified, 85% efficient diesel particulate filters. The retrofit begins in 2003 and will be completed through 2007.
• New bus engines have to be certified to increasingly more stringent emission standards (Table 5).
• Ultimately, 15% of new purchases have to be zero emission buses, ZEB (Table 5).
The urban transit bus fleet rule requirements and emission standards are summarized in the following table.
California Urban Transit Bus Fleet Rule
Date Diesel Path Alternative Fuel Path . NOx, g/bhp•hr PM, g/bhp•hr NOx, g/bhp•hr PM, g/bhp•hr 2000 4.0 0.05 2.5* 0.05 7/2002 Ultra low sulfur diesel fuel Ultra low sulfur diesel fuel 10/2002 2.5 NOx+NMHC 0.01 1.8 NOx+NMHC* 0.03 10/2002 4.8 NOx fleet average 4.8 NOx fleet average 07/2003 Diesel particulate filter retrofit Diesel particulate filter retrofit 07/2003 3 ZEBs for large fleets (>200) . 2004 0.5 0.01 . . 2007 0.2 0.01 0.2 0.01 2008 15% of ZEBs for large fleets (>200) . 2010 . 15% of ZEBs for large fleets (>200) Notes: Shaded areas show existing requirements and existing optional emission standards * - Optional standards. Although transit agencies on the alternative-fuel path are not required to purchase engines certified to these optional standards, it is expected that they will do so in order to qualify for incentive funding.
Model Year 2007 and Later
On December 21, 2000 the EPA signed emission standards for model year 2007 and later heavy-duty highway engines (the California ARB adopted virtually identical 2007 heavy-duty engine standards in October 2001). The rule includes two components: (1) emission standards, and (2) diesel fuel regulation.
The first component of the regulation introduces new, very stringent emission standards, as follows:
The PM emission standard will take full effect in the 2007 heavy-duty engine model year. The NOx and NMHC standards will be phased in for diesel engines between 2007 and 2010. The phase-in would be on a percent-of-sales basis: 50% from 2007 to 2009 and 100% in 2010 (gasoline engines are subject to these standards based on a phase-in requiring 50% compliance in 2008 and 100% compliance in 2009).
Emission certification requirements also include the SET test, with limits equal to the FTP standards, and NTE limits of 1.5 × FTP standards.
Effective 2007 model year, the regulation also eliminates the earlier crankcase emission control exception for turbocharged heavy-duty diesel engines. Crankcase emissions from these engines are treated the same as (i.e., added to) other exhaust emissions. Manufacturers are expected to control crankcase emissions by routing them back to the engine intake or to the exhaust stream upstream of the exhaust emission control devices.
The diesel fuel regulation limits the sulfur content in on-highway diesel fuel to 15 ppm (wt.), down from the previous 500 ppm. Refiners will be required to start producing the 15 ppm S fuel beginning June 1, 2006. At the terminal level, highway diesel fuel sold as low sulfur fuel must meet the 15 ppm> sulfur standard as of July 15, 2006. For retail stations and wholesale purchasers, highway diesel fuel sold as low sulfur fuel must meet the 15 ppm sulfur standard by September 1, 2006.
Refiners can also take advantage of a temporary compliance option that will allow them to continue producing 500 ppm> fuel in 20% of the volume of diesel fuel they produce until December 31, 2009. In addition, refiners can participate in an averaging, banking and trading program with other refiners in their geographic area.>
Ultra low sulfur diesel fuel has been introduced as a “technology enabler” to pave the way for advanced, sulfur-intolerant exhaust emission control technologies, such as catalytic diesel particulate filters and >NOx catalysts, which will be necessary to meet the 2007 emission standards.
The EPA estimates the cost of reducing the sulfur content of diesel fuel will result in a fuel price increase of approximately 4.5 to 5 cents per gallon. The EPA also estimates that the new emission standards will cause an increase in vehicle costs between $1,200 to $1,900 (for comparison, new heavy-duty trucks typically cost up to $150,000 and buses up to $250,000).
Source: DieselNet Web Site. Retrieved October 4, 2004 from www.dieselnet.com/standards/us/hd.html