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US EPA proposes Tier 2 emission standards for light duty vehicles

3 May 1999

The US EPA has unveiled proposed Tier 2 (year 2004) emission standards for light duty vehicles, including cars, minivans, sport utility vehicles (SUV), and light duty trucks. The proposal was presented on Saturday, May 1st by President Clinton.

The same emission standards have been proposed for all vehicles, regardless of the type of fuel they use. That is, vehicles fueled by gasoline, diesel, or alternative fuels all must meet the same standards.

The proposed Tier 2 regulation is accompanied by a proposed gasoline sulfur standards for refineries. Low sulfur gasoline is believed to be necessary for advanced and durable emission control catalyst technologies that will be required. The cleaner gasoline and tougher tailpipe emissions standards would be phased in over five years, beginning in 2004.

At the same time, the EPA issued an Advanced Notice of Proposed Rulemaking (ANPRM) on the quality of diesel fuel. An increasing share of diesel engines is expected in the light duty truck (LDT) vehicle category. The ANPRM is outlining the considered new quality requirements for diesel fuel, including lowering the sulfur level, to enable the use of new generation emission control technologies for diesel fueled vehicles.

The new standards have been hailed by environmental groups and criticized by the industry and several Republican politicians. Publication of the proposed rules opens a public comment period. The proposal may be modified during the public discussion process before it becomes the final rule.

Proposed Vehicle Emission Standards. The proposed tailpipe standards would be structured into 7 certification levels of different stringency, called EPA bins, and an average standard for oxides of nitrogen (NOx) emissions to be met by vehicle fleets sold by each manufacturer.

The fleet average NOx standard would be set at 0.07 grams per mile (g/mi) for all classes of passenger vehicles, including light-duty trucks, such as the largest SUVs. Vehicles weighing less than 6000 pounds (such as cars) would be phased-in to this standard between 2004 and 2007.

For the heaviest light-duty trucks (such as bigger SUVs), the proposal provides a three-step phase-in program. In 2004, a standard of 0.6 g/mi NOx would be implemented. An interim standard of 0.2 g/mi would be phased-in between 2004-2007. In the final step, 50% of these vehicles would meet the 0.07 standard in 2008, and the remaining 50% will comply in 2009.

Current Tier 1 NOx standards range from 0.4 g/mi for cars (1.0 g/mi for diesel cars) to 1.1 g/mi for LDTs over 5,750 lbs.

There is no fleet average standard for particulate matter (PM) emissions. The PM standards for the particular certification bins range from 0 (bin 1, zero emission vehicle), through 0.01 g/mi (bins 2-5), to 0.02 (bins 6 and 7). Current Tier 1 PM standard for diesel cars is 0.08 g/mi.

Proposed Sulfur Levels in Gasoline. The nation’s refiners would meet an average sulfur level of 30 parts per million (ppm) by 2004, down from the current average of more than 300 ppm. The maximum amount of sulfur in gasoline, for purposes of averaging, would be capped at 80 ppm, after a three-year phase-in.

Small refiners would have an additional four years to comply, with the opportunity of an extension for those that can demonstrate a severe economic hardship.

Diesel Fuel Quality. In the published ANPRM, EPA is not proposing any particular sulfur level in diesel fuel. Rather, the document is soliciting comments on what sulfur levels are needed and when. However, the ANPRM quotes a sulfur level of 30 ppm as the number desired by engine industry. Comments are solicited on the feasibility of reducing sulfur in diesel fuels to 5, 10, 30, and 50 ppm.

Current maximum diesel fuel sulfur level in the US is 500 ppm. Ultra low sulfur fuels may open the door for new emission control technologies such as lean-NOx traps/catalysts. Without these technologies diesel fueled cars and LDTs are not likely to be able to meet the proposed Tier 2 standards.

Environmental Benefits. The EPA estimates that, when fully implemented in 2030, the proposed tailpipe standards would reduce NOx emissions from vehicles by about 74%. The proposed standards also would reduce emissions of particulate matter, or soot, from vehicles by about 84%.

Costs of Program. According to EPA estimates, implementing program would come at an average cost increase of less than $100 per car and less than $200 per light-truck. Consumers would pay less than 2 cents per gallon more for gasoline, or about $100 more over the life of an average vehicle.

According to the industry, the new standards would force auto makers to spend billions of dollars to comply, adding $200 to the average sticker price of a new car. Oil refiners predicted the average price of gasoline could rise as much as 6 cents a gallon because of the cost involved in upgrading refineries.

Tier 2/gasoline sulfur rulemaking documents
ANPRM - diesel fuel

Source: US EPA