Converter Recycling: The Cats Of The Future Are Not Simple

A few years ago, I shared this overview of how exhaust systems and converter loadings are changing. Peter Duncan, General Manager of Market Research for Johnson Matthey, had shown us how the exhaust systems were changing to include more and complex catalytic converters that have different loadings and functions—some converters not even containing precious metals.

If you are selling by the piece, there is more room than ever for shades of gray when it comes to pricing. We encourage our customers to sell converters on assay, or the precious metal content within the converter, which eliminates the grading subjectivity.

Loadings and Trends
Basically, the tighter the emission standards, the higher the PGM (platinum group metal) loadings or cat value. The United States is predominantly gasoline engine vehicles, whereas Europe is predominantly diesel engine vehicles. More than 90 percent of catalytic converter applications are made of a ceramic monolithic substrate, or honeycomb material; the remainder are metallic monolith substrates, commonly called foils or wires. The problem is no longer being able to identify and price ceramic and metallic converters, but rather something different.

Where the new recycling challenge emerges is the complexity of the exhaust system architectures for both gasoline and diesel engine vehicles. The new components may all look like cats, but they do not all have value; processing some of these components with others can even ruin a load.

Gasoline engines emit lower soot than diesel engines under typical driving conditions. Most gasoline engine vehicles contain a combination of traditional ceramic three-way catalyst (TWC). However, gasoline particulate filters (GPFs) are being added to these systems. Diesel systems can have up to 4 components to handle emissions: the diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), a lean NOx trap (LNT), and some type of selective catalytic reduction catalyst (SCR) or selective catalytic reduction filter (SCRF).

All the above-mentioned components, which resemble catalytic converters, have various amounts of PGMs, some, like SCRs and SCRFs are PGM-free.

In terms of PGM loadings, the DOCs, diesel oxidation catalysts are like regular gasoline catalysts, having even higher loadings. DPFs, diesel particulate filters, have some value, generally low.  DPFs can have one of two bases: aluminum titanate (ATI) or silicon carbide (SiC). Silicon carbide-based DPFs must be processed separately at higher temperatures with oxidation to avoid combustion. This represents higher recycling costs and when comingled can lead to lower metal yields.  SCRs and SCRFs, selective catalytic reduction catalysts and filters are PGM free, having zero value.  LNTs, Lean NOx traps have some value, albeit low.

Whether you are buying or selling converters by the piece, these complex exhaust system architectures are beginning to pose a problem in identifying, grading, and pricing. This to say, buyer and seller beware.

Future Powertrains and PGMs
You may be wondering about future powertrains and how they may affect the demand and use of PGMs. Even with the 2030 zero emission mandates, these powertrains are unlikely to completely replace the internal combustion engine (ICE) market but will for the most part contain similar or higher PGM loadings. Gasoline turbo direct injection (GTDI) engines have better fuel efficiency but higher hydrocarbon and particulate emissions; these will result in higher PGM use. Lean burn gasoline (LBG)engines also have better fuel efficiency but higher NOx emissions requiring LNTs and thus more PGM use. Battery electric vehicles (BEV) require no PGMs. Hybrid electric vehicles (HEV) with their “cold start” will require 10-15% more PGMs. Finally, fuel cell electric vehicles (FCEV) which are platinum heavy will also increase PGM use.

If you have questions about this article or any issue pertaining to the recovery of precious metals and materials from automotive recycling, we, at United Catalyst, are here to help you. United Catalyst Corporation is a processor of scrap catalytic converters that offers global refining services. Our recycling solutions are accurate, scientific, and verifiable to get you the most money. United Catalyst is a processor you can trust.

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Becky Berube serves the recycling community as President of United Catalyst Corporation, Co-Chair of the Automotive Recycling Association’s Events Advisory Committee, and is an ExCom Board Member of the International Precious Metals Institute. She can be reached at 864-834-2003 or by email at