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Frequently asked questions on SCR systems and recycling

on May 3, 2019

One of the most common questions we receive these days is, “Do you guys recycle SCR systems?” While our answer is generally no, this is a complex topic in which we’d like to provide some clarity in a quick FAQ about SCR systems and how manage their disposal at the end of their useful life.

1. Q: What are SCR systems?

A: SCR stands for selective catalytic reduction and it is an emission control technology primarily used to reduce NOx emissions from diesel engines, industrial boilers and gas turbines.

2. Q: How do SCR systems work to reduce NOx from diesel engines?

A: Very basically, SCR is a mechanism to convert oxides of nitrogen (NOx) to nitrogen (N2) and water (H2O) by adding a gaseous reductant, typically ammonia or urea, to an exhaust stream.

3. Q: Why are there so many SCR systems running on trucks today?

A:  In 2010, the US EPA ratcheted down the allowable NOx emissions from diesel truck engines to 0.2 g/bhp-hr.  In order to meet this low NOx emission standard, many engine manufacturers chose to utilize SCR as the technology to achieve the standard.

4. Q: Did all OEMs utilize SCR to achieve the 2010 standard?

A: No.  Some OEMs utilized advanced exhaust gas recirculation (EGR) to meet the standards, however that technology has been largley abandoned and now all heavy-duty engine OEMs are using SCR to achieve emissions standards.

5. Q: Why have there been so many SCR systems coming off trucks in the last 12 months?

A: In July of 2018, Cummins announced a voluntary recall of 500,000 medium and heavy-duty truck engines due to a defective part in the SCR system. Truck dealers are now performing these recalls and generating large volumes of scrap SCR systems.  Unfortunately, Red Fox Resources does not buy these systems.

6. Q: Does Red Fox buy used/spent SCR systems?

A:  No.  Unlike most of the diesel particulate filters and diesel oxidation catalysts that Red Fox buys back for recycling, SCR systems do not contain enough platinum group metals to feasibly recover through recycling.

7. Q: How does Red Fox recommend disposing of used SCR systems?

A:  We recommend you process these parts along with your standard scrap metal.  You should check with your local metals recycler to make sure they accept these types of systems.  Red Fox can provide documentation of the contents should they ask.

8. Q: How can I identify an SCR system that should be scrapped vs a DPF or DOC that is recyclable?

A: Generally speaking, SCR systems are identifiable because they are much larger than singular DPFs and DOCs.  DPFs and DOCs are designed so that the individual components can be removed for service.  Most of the 2010 SCR systems are non-modular, meaning they cannot be unbolted to be serviced individually.  While the diameters of the DPF, DOC and SCR systems can be the same, the length of the SCR will be much longer.  Generally, SCR systems are 35” – 45” long, where the DPFs and DOCs would be 4”-16” long.

9. Q: Detroit uses a One-box technology that includes the DPF, DOC and SCR in one box, does Red Fox recycle Detroit One-boxes?

A: Yes.  Red Fox will buy a complete One-box system for the PGM contained in the DPFs and DOCs.

10. Q: Volvo uses an SCR system that resembles a Detroit One-box, do you accept Volvo SCR systems?

A: No.  The Volvo SCR system (pictured below) does not include the DPF and DOC like the Detroit system so we do not accept or recycle Volvo or Mack SCR systems.

11. Q: I’m not sure if a part is an SCR or DPF or DOC, what should I do?

A:  Snap a picture and send it to our buying group at 415-793-3439 or email it to  Our experts will take a quick look and let you know what you’ve got and if we would buy it back for recycling or recommend it be scrapped locally.

To learn more about DPF and DOC recycling, visit the Red Fox Resources FAQ page or contact us to get a quote at 1-844-733-3695.

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Tripp HellerFrequently asked questions on SCR systems and recycling