The Environmental Protection Agency has updated its guidance for certification of truck engines using selective catalytic reduction to reduce emissions, calling on SCR engine makers to develop warning systems that alert drivers when the truck’s diesel exhaust fluid tank is nearly empty or filled with a liquid other than DEF.
The new guidance, mostly in response to claims made by Navistar Inc. that SCR technology can be circumvented, also urged OEMs using SCR to research methods that would inhibit tampering with SCR system operation and incorporate further inducements for drivers to comply.
Concerns about SCR’s environmental compliance were brought to EPA’s attention by Navistar, which uses a competitive technology, exhaust gas recirculation, to meet EPA 2010 regulations. Navistar had sued both EPA and the California Air Resources Board over their acceptance of SCR technology without stronger measures to prevent engine operation without DEF or an operational SCR system. The truckmaker last year settled both lawsuits by garnering a commitment for further review.
Navistar representatives contended that independent test findings showed new commercial vehicles that must contain liquid urea to meet federal NOx emissions standards continued to operate effectively when urea was not present. At such times, Navistar said, the vehicles threw off levels of NOx as much as 10 times higher than when urea was present.