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Catalytic Converters Leave a Trace of Platinum behind

Author: Peter Thompson

Detroit/Bonn - In the fall of 2004, industry experts celebrated the 30th anniversary of the catalytic converter. "30 years of cleaner air" and "industry milestone" were some of the flowery phrases. Behind the story of brilliance is one of failures. The recycling of catalytic converters is still insufficient. Within the last ten years, 65 percent of the precious metals adopted in these converters worldwide were lost. According to sources in the American automotive industry, 25 percent of the precious metals were dispersed on the roads and a further 36 percent did not reach the converter recycling due to insufficient collection. Cars are leaving a trace of platinum, palladium and rhodium behind. In 2003, the total value of precious metals and stainless steel used worldwide for the production of catalytic converters for vehicles exceeded $ 4 billion. Stainless steel is used for the heat resistance and rust-proof housing. It contains a ceramic honeycomb which is covered by the catalyst metals platinum, palladium or rhodium or a mixture of these metals (PGM - Platinum Group Metals). The honeycomb is embedded in a ceramic fiber mat. Over half of the world´s PGM production is used in vehicle catalytic converters. This is not a huge quantity in a traditional sense but an enormous value. The total platinum production amounts to 193 tons annually, or respectively 6.2 million ounces. According to statistics of North-American recycling companies and precious metal experts, in the past ten years on average, only 35 percent of the precious metals used in the manufacturing of catalytic converters were recovered. 65 percent were lost.

The losses occurred during the use of the vehicles, at the collection of the converters in scrap yards and repair shops, in the processing of the converters and during smelting of the precious metals. During the operation of the vehicle, statistically 25 percent of the PGM leave the housing - not more than five percent due to normal wear and the rest due to damage or destruction of the honeycomb corpus. A further 36 percent of the originally contained precious metals do not enter the recycling because collection logistics are insufficient. The vehicles are shreddered together with the converters or the complete exhaust gas systems are dismounted by car recyclers for resale and later forgotten, meaning the converters will also be recycled together with steel or stainless steel scrap. Of course there are also abandoned vehicles and exports to countries without recycling systems.

About two percent of the precious metals are lost during separation of the housing from the honeycomb, so-called decanning. They disappear through dust filter systems or adhere to the housings. A further two percent of the loss can be ascribed to the melting and refining process. The milled material of ceramic and precious metal powder has a higher PGM concentration than is found in PGM ores. One thing is obvious: precious metals coming closer to the final recovery are processed more and more carefully.

A major US scrap converter processor tracked the losses. In 2003, more than 50,000 used converters delivered by collectors were examined. The data showed that 11 percent of the converters were empty. A further 12 percent were partially empty. It is assumed that those numbers are only a partial result as empty converters are less attractive for collection companies and partially sorted out in advance. Considering the normal wear, it can be finally concluded that about 25 percent of the precious metals are lost during the use of the vehicle. Converters which do not reach the first recycling step, separation from the vehicle and collection, could of course not be examined by the company. A comparison of the total recycling efficiency showed a close compliance with the record of the precious metal producers. Those assume that catalyst metals on the average remain for ten to twelve years in the vehicles and therefore the flow back time is delayed. The whole branch is aiming at a decrease of the precious metal losses. The experts see  a realistic scenario by 2015: cutting in half the in-use-losses with more robust converters and the improvement of the collection efficiency by ten percent. This would mean an additional amount of precious metals and stainless steel that could be reused, worth well over $ 400 million per year at today´s prices.