21 December 2000 | updated 2 January 2001

The Clinton administration announced that it has adopted the final emission standards for new model year 2007 heavy-duty diesel engines and the fuel sulfur rule. The final regulation, signed on December 20, follows closely the EPA proposal published on May 17. The biggest difference is a phase-in 2006-2010 schedule for the introduction of ultra low sulfur fuel, as opposed to a nationwide deadline of mid-2006 in the original proposal.

The adopted emission standards are 0.01 g/bhp-hr for particulate matter (PM), 0.20 g/bhp-hr for nitrogen oxides (NOx), and 0.14 g/bhp-hr for nonmethane hydrocarbons (NMHC). The PM standard will take full effect in 2007, while the NOx and NMHC standards will be phased in for diesel engines between 2007 and 2010. Compared with today’s standards, the new rule represents a 95% reduction in the NOx level (currently at 4 g/bhp-hr; an intermediate standard of 2.4 g/bhp-hr of combined NOx+NMHC takes affect in 2004/10.2002) and an 80-90% reduction in PM emission (currently at 0.1 for truck engines and 0.05 g/bhp-hr for urban buses).

Exhaust aftertreatment technologies that are expected to be required to meet the new standards are not tolerant to sulfur. Therefore, as a “technology enabler”, the regulation establishes a maximum sulfur level in highway diesel fuel at 15 ppm (by weight), down from today’s 500 ppm. A phase-in schedule that has been adopted requires 80% of all highway fuel meeting the 15 ppm sulfur specification by September 2006, and nationwide availability by 2010.

The adopted 2007 emission standards represent a landmark regulation of unprecedented stringency. Unlike cars which commonly use catalytic converters, most of current heavy-duty engines rely on engine technologies to meet emission regulations and have not been using emission aftertreatment devices. The USA has followed the lead of the European Union in adopting emission standards that are designed to force emission aftertreatment devices on heavy duty diesel engines. The first such “aftertreatment-forcing” regulation worldwide was the Euro 4/5 (2005/2008) standard, adopted by the European Parliament in November 1999 and published in December 1999. The current EPA 2007 rule, however, sets emission limits that are much tighter than those adopted in the EU, becoming the most stringent diesel emission standard worldwide.

Some of the US oil industry has been opposing the 15 ppm fuel sulfur cap arguing it would cause high and unnecessary costs to upgrade refineries. The American Petroleum Institute estimated the rule will increase the cost of fuel by at least 15 cents a gallon and cause “a significant risk of (fuel) shortages” by 2007. The EPA estimated the additional cost at 4 - 5 cents. The EPA also estimated that the costs of the program will raise costs of new vehicles by $1,200 to $1,900 per vehicle (new trucks cost up to $150,000 and buses cost up to $250,000).

The adopted emission regulation poses a significant technological challenge. The emission standards are tailored to force the use of diesel particulate filters on new heavy-duty engines. Some form of NOx catalysts will be also required for nitrogen oxides control. The EPA believes that the NOx adsorber-catalyst technology will mature enough to allow for the 2007-2010 implementation, as stipulated in the standard. This technology, however, is still under development and has not yet been demonstrated on heavy duty engines. Urea-SCR would be a fall-back option, in case the NOx adsorber technology is not developed on time.

Mixed response could be heard after the announcement. The new regulation was applauded by environmental organizations. The diesel and automotive industries supported the introduction of 15 ppm fuel sulfur cap, but generally commented that the emission standards may not be feasible. There is a split in the oil industry. While some companies already perceive the ultra low sulfur fuel as a new business opportunity, others are in strong opposition. Some oil companies are expected to ask the incoming Republican administration of George W. Bush to set the diesel sulfur cap at 50 ppm, rather than 15 ppm.

Source: US EPA