Spark Plug Recycling Is A Thing, Because Iridium Is Too Expensive

You may not think much about the spark plugs in your car's engine, but those small devices require precision manufacturing and valuable metals to keep your vehicle humming. It's not unusual for a typical spark plug to feature steel, copper, and nickel, but many contain rare earth metals like platinum and iridium to extend the service life while maintaining engine performance. Iridium, in particular, is what makes these plugs among the longest-lasting of the many spark plug types, since it's the most corrosion-resistant material known to humanity. Iridium is extremely hard, dense, and has a melting point of over 4,400 degrees Fahrenheit, making it well suited for automotive and performance applications.

However, it so happens that iridium is also one of the rarest elements on the planet, with the Earth's crust only having around 0.000003 parts per million of iridium. Its rarity and superior properties are why iridium plugs are almost double the price of platinum plugs, but car engines are only a small part of the growing worldwide demand for iridium. The electrochemical industry uses about 3.1 tons of iridium annually, while electronics manufacturers consume 2 tons of it on average.

For spark plugs it's about 1.7 tons per year, which costs about $430 million based on the current market price of $7,900 per ounce of iridium. So yeah, iridium is rare, hard to get (mostly gathered from byproducts of nickel refining), and quite expensive. It is this conundrum that led new and innovative industry players to look into recycling iridium and other precious metals from old and used spark plugs. With iridium being scarce and with demand growing each year, we can only mine too much of it before it's gone.

It used to be that old spark plugs would end up in landfills or scrapyards for their steel content, with no efforts to recover the iridium or platinum content. In most cases, recyclers will grind the iridium and platinum and mix them with the scrap steel, which essentially ends their lifecycle. It wasn't until 2021 that spark plug recycling became a thing, and we know why it took so long for industries to catch up in recovering the many precious metals that make up a spark plug.

For one thing, iridium's hardness, very high melting point, and the low quantities of it in each plug previously made it difficult to extract for recycling. Earlier attempts to recover precious metals from discarded spark plugs were either too inefficient or labor-intensive to make sense economically. It's the same story with platinum. You probably know the differences between platinum and iridium spark plugs, but platinum is also one of the rarest precious metal in the world (rarer than gold, think about that). And with a 3,214-degree Fahrenheit melting point, platinum is also difficult to recycle. Even though 90% of the platinum in catalytic converters is recovered and reused, global recycling has declined by 17% as of 2024.

However, things started to look up in 2023, when PGM Recovery, now rebranded Noble6, received a patent for an automated system that extracts precious metals like iridium and platinum from spark plug electrodes. Its business model is a win-win, since shops and garages can ship used spark plugs and get paid, while manufacturers can reuse or repurpose the recycled metals to reduce their dependence on raw materials.

It's hard to discern the environmental impact of something as common as a spark plug, but it's substantial. A huge chunk of cash in the manufacturing of spark plugs goes directly to the procurement of copper, platinum, and iridium. Extracting those precious metals from the earth consumes resources, contaminates the soil, disrupts the ecological balance of the area and its surroundings, and pollutes the air with greenhouse gas emissions from the machinery and equipment required for mining and extraction.

With 85% of global iridium production coming from South Africa and Zimbabwe, there are humanitarian benefits to spark plug recycling, too, with miners often succumbing to silica exposure that leads to tuberculosis and irreversible silicosis. Reducing our global dependency on freshly mined rare earth metals will help preserve whatever is left of our planet's natural resources, help clean the air, and lower the cost of production, which is good for your car and your wallet.

If you want to be part of the spark plug recycling movement, you can get paid by sending old spark plugs in bulk to Noble6. However, they only accept platinum and iridium plugs (double platinum plugs with more platinum content than ordinary platinum plugs are included) that are undamaged, clean, and have no oily stains or residues.