19 January 2012

A US District Court in Washington, DC dismissed a complaint by Navistar against the Environmental Protection Agency (EPA), where the engine maker attempted to force the agency to recall competitors’ urea-SCR engines as noncompliant with the Clean Air Act (CAA), according to a report by Courthouse News. Judge Colleen Kollar-Kotelly also rejected Navistar’s request for discovery and allowed intervention by the competing manufacturers: Cummins, Daimler Trucks North America, Detroit Diesel, Mack Trucks and Volvo Group North America.

Navistar claimed that 2010 heavy-duty engines utilizing SCR aftertreatment—based on liquid urea reductant (DEF/AdBlue) injected upstream of SCR catalyst—violate emission standards when in on-road use. The company asked the court to grant it “significant discovery” related to the emission nonconformance of the engines. Furthermore—according to Navistar—the EPA had determined that the engines are not designed consistently with air quality regulations. Therefore, the agency must order a mandatory recall under the CAA. Navistar said it was taking this action to reduce what it viewed as “illegal favoritism towards companies producing engines with SCR technology” by the EPA.

The court found, however, that the EPA has never determined SCR engines were noncompliant and that Navistar failed to cite a single EPA document that actually said SCR diesel engines did not conform to the relevant emission regulations. The court ruled that the record does not support the allegation that the EPA violated statute and let noncompliant engines remain on the road by failing to recall them.

Navistar is the only heavy-duty engine manufacturer who chose in-cylinder NOx reduction methods, such as low temperature combustion with high EGR rates, to comply with the US 2010 emission standards. All of the competing manufacturers chose to control NOx via urea-SCR aftertreatment—a method that allows to calibrate the engine for higher engine-out NOx emissions, better fuel economy and lower CO2 emissions. The SCR pathway, due to the higher NOx, also allows to rely to a larger degree on passive regeneration of diesel particulate filters (DPF). This is a source of a further fuel consumption benefit compared to non-SCR engines that are subject to a fuel economy penalty for active DPF regeneration.

A 2010 Navistar-commissioned study by EnSIGHT concluded that the safeguards built into 2010 SCR trucks were inadequate, making it possible to operate SCR engines for periods of time without urea solutions or with urea tanks filled with water in place of urea, which resulted in excessive NOx emissions. Navistar also pointed out that SCR systems are not efficient at low exhaust temperatures, such as encountered during slow urban driving.

In 2011, partly in response to the Navistar findings, the EPA tightened their certification requirements for engines with urea-SCR (“Guidance on EPA's Certification Requirements for Heavy-Duty Diesel Engines Using Selective Catalytic Reduction Technology”). The EPA Guidance requires that SCR vehicles be fitted with driver warning and “inducement” systems that make it impossible to operate vehicles without urea solution in the tank. The revised guidance called for enhancements to the low urea level warning system. If the urea tank gets empty or if a urea dosing malfunction is detected, the revised guidance suggested that the vehicle be slowed down to 5 mph. The guidance also required detecting of poor quality urea or the use of other fluids and called on manufacturers to devise methods to prevent tampering.

While tightening the requirements, the EPA said it did not believe Navistar’s findings reflected the overall efficacy of SCR systems on heavy-duty diesel engines that were in operation on the road. Most of Navistar’s findings—said the agency—resulted from actions by the contractor’s drivers to intentionally circumvent the manufacturer-designed inducements of the test vehicles. For example, drivers avoided triggering inducements associated with an empty urea tank by limiting refueling quantities or keeping the truck running when it normally would be turned off. Both ways of circumventing the inducements exact their own costs on drivers in terms of time, convenience, and expense. That view was shared by Judge Kollar-Kotelly, who said in her ruling that EPA and truck makers cannot be held responsible for deliberate misuse of SCR systems.

Navistar’s 2010 and later engines are typically certified to NOx emission levels of 0.4-0.5 g/bhp-hr, with the difference from the 0.2 g NOx standard being covered by NOx emission credits. According to recent California ARB emission certificates for Navistar engines, the company may run out of credits as early as the end of February 2012. If Navistar must supply engines certified to the 0.2 g NOx standard, further deterioration in fuel economy may be difficult to avoid—a realization that caused nervousness among investors and a drop in Navistar share price, reports the Wall Street Journal.

Source: Courthouse News