EPA revises SCR guidance for 2010 emissions

The U.S. Environmental Protection Agency (EPA) revised its 2010 engine emissions guidance limiting the number of miles and hours a vehicle using selective catayltic reduction (SCR) technology can operate after the diesel exhaust fluid (DEF) is exhausted.

The original guidance issued in February 2009 required engine performance to be degraded after a truck travels 2,000 miles or 40 hours on an empty DEF tank. The revision removes this provision and eliminates any suggested limits on mileage or time trucks should operate with empty DEF tanks.

In a December 30, 2009, letter to engine manufacturers, Karl Simon, director of compliance and innovative strategies at EPA’s Office of Transportation and Air Quality, explained the revision as clarification in a misunderstanding of the intent of the guidance.

“Because some prescriptive language in CISD-09-04 may have led to confusion regarding our intent that the document be used as guidance, rather than setting forth binding requirements, I believe it is appropriate to provide a new document providing revised guidance regarding certification of heavy-duty diesel engines using SCR,” says Simon.

The guidance revision follows a law suit filed against the EPA by Navistar last year. Navistar claims the 2009 guidance was a “license to pollute.” The EPA asked the U.S. Court of Appeals for a 60-day stay to halt legal proceedings in October 2009 in order to revise the guidance to meet Navistar’s demands.