EPA Warns of Possible Dioxins In Cummins’ 2010 SCR System
By Frederick Kiel, Staff Reporter
This story appears in the Jan. 12 print edition of Transport Topics.
The Environmental Protection Agency said it is concerned that emissions systems using a copper compound that engine maker Cummins Inc. will use in 2010 models could generate “likely human carcinogen” dioxins, in which case it would “likely not certify” the systems.
In a Dec. 11 letter, EPA said that it would do its own testing on engines with a selective catalytic reduction system that utilizes copper zeolite.
The EPA testing could lead to rejecting engines using copper zeolite, even if the tests are inconclusive, the agency said. A Cummins spokesman said the company was “cooperating” with EPA.
“EPA has a long-standing concern that copper has the potential to catalyze dioxin formation in conditions experienced in incinerators and in diesel exhaust,” said Karl Simon, director of EPA’s Compliance and Innovative Strategies Division, in a letter to engine manufacturers.
As a result, Simon wrote, “questions have been raised regarding the potential for copper-containing diesel SCR catalysts to promote the formation of dioxin compounds.”
All heavy-duty engine makers except Navistar Inc. said they will use SCR to meet EPA mandates for drastically reduced nitrogen oxide emissions beginning Jan. 1, 2010, but all except Cummins plan to use iron zeolite rather than copper.
SCR uses a catalytic converter in the exhaust system to remove NOx; the converter requires a mixture of urea and water called Diesel Exhaust Fluid.
Spokesmen from Volvo Trucks North America, Mack Trucks Inc., Detroit Diesel Corp., and Paccar Inc., all told Transport Topics that their SCR systems will utilize iron zeolite, not copper zeolite.
Mack Trucks spokesman John Walsh said his company “uses iron zeolite in our SCR system. We did look at copper zeolite, but decided not to use it for a couple of reasons.”
He said that the performance difference between iron zeolite and copper zeolite was “difficult to even measure.”
“Copper zeolite also costs more and is more sensitive to ultra-low-sulfur fuel than iron zeolite,” Walsh said. “And we were aware that the use of copper zeolite could result in the formation of undesirable and potentially harmful compounds.”
When Cummins reversed its plan to rely on exhaust gas recirculation alone to meet EPA mandates, which treats NOx within the engine, it cited copper zeolite as a main reason to shift to SCR.
“The development of copper zeolite for a catalyst that has very good properties for NOx conversion has allowed us to optimize engine and after-treatment performance, for better fuel mileage and meet EPA standards,” Steve Charlton, Cummins’ vice president of heavy-duty engineering, told reporters Aug. 13 (click here for previous Premium Content story). “It’s a new matter with very good thermal performance that we’ll use downstream of the diesel particulate filter, where emissions can leave at 500 to 600 degrees Celsius.”
“The molecular structure of copper zeolite has some very interesting properties that is very favorable to fuel, and the interaction of NOx and urea,” Charlton added.
Cummins spokeswoman Christy Nycz said last week that the company has received the EPA letter expressing concern.
“This did not come as a surprise, as Cummins has had discussions with the EPA previously on this subject,” Nycz told TT.
“Cummins is cooperating with the EPA on their request for testing and resulting data,” Nycz added. “Currently, the EPA is working on a test methodology, and an independent research firm will be conducting their tests.”
She said that “in accordance with the guidance letter, Cummins will be conducting our own tests and will provide the data to the EPA.”
EPA spokeswoman Catherine Milbourn said, “It’s really too premature to say anything at this point, and we really don’t know if there is anything to this at all.”
Simon’s letter listed EPA concerns. “Dioxins have a number of adverse non-carcinogenic health effects, including effects on the reproductive system, the developing fetus and the immune system,” he wrote.
“Dioxins have been characterized by EPA as likely human carcinogens and are anticipated to increase the risk of cancer at background levels of exposure. An increase in dioxin emissions from any source sector is considered a potentially serious issue by the EPA,” he wrote.
The letter said that EPA could likely ban copper zeolite SCR systems even if tests were inconclusive.
“Data from this plan, and any other relevant data EPA receives, will help determine how we will address this issue for future certification applications that include copper-zeolite catalysts,” the letter said. “For example, if the data are inconclusive or show increased dioxin emissions, then EPA likely will not certify an engine family utilizing such products unless a manufacturer can provide data which demonstrates the intended use of the copper catalyst doesn’t increase dioxin emissions.”
The EPA gave no date when test results may be final.
