Is Stainless Steel Biodegradable?

Stainless steel is used commonly in cookware, cutlery, water bottles like Hydro Flask and a variety of other products. Sometimes it finds its way into landfill. When this happens is stainless steel biodegradable?

I recently learned that you can recycle stainless steel but not in your curb side bin collection, which makes it hard. So I wanted to know if I just threw away my Hydro Flask or stainless steel product, will it biodegrade over time and how long will it take to do so?

Stainless steel is 100% recyclable but it is not biodegradable. Over time stainless steel will rust and flake into the ground/atmosphere but it does not biodegrade as organisms in landfill do not consume metal particles for nutrition.

The very definition of biodegradable according to the oxford dictionary is “a substance capable of being decomposed by bacteria or other living organisms and thereby avoiding pollution.”

But while it's not biodegradable does stainless steel break down into something more natural over time and how long does this process take?

How Long Does Stainless Steel Take To Break Down?

Stainless steel is designed to be rust resistant and thus resistant to breaking down.

Depending on the quality and grade of the stainless steel as well as the environment it is in it could take anywhere from 100-1,000+ years for stainless steel to completely break down back into more natural element.

Estimated time (in years) to corrode 1mm of stainless steel by type according to BSSA:

Ocean145 years260 years
Semi-industrial85 years135 years525 years
Rural250 years770 years1,200 years

Corrosive environments like near the ocean where the stainless steel is constantly exposed to heat, salt spray, humidity and wind will cause the metal to rust more quickly.

If the stainless steel is kept somewhere cold with very little moisture then it may take decades for any rust to appear, let alone completely break down the stainless steel.

Metals like nickel and chromium are added to stainless steel to make to corrosion resistant, meaning it can take much longer than other metals to completely break down.

So stainless steel that is thrown away into landfill and not recycled will likely still be there in hundreds if not thousands of years. It's not biodegradable and it's designed to not break down or rust easily.

Stainless Steel Can Be Infinitely Recycled

While it's not biodegradable and while it takes hundreds to thousands of years to break down the good news is that stainless steel is recyclable over and over again.

This makes it extremely environmentally friendly. In fact, any stainless steel object has around 40-60% of recycled material within it.

Stainless steel does also not degrade as it is recycled. This means old stainless steel can be used to make high quality steel over and over again.

The only problem is that in most areas you can't recycle your stainless steel saucepans, cutlery or old water bottle in your curb side collection. You instead need to hunt down a scrap metal recycler and see if they will take your small amounts of scrap metal off your hands.

They may pay you a little bit for it, they may take it for free just so you have the good conscience of knowing it'll get reused or maybe they won't take such small amounts.

Hopefully in the future recycling stainless steel household items will become easier so that more of it can be reused and less of it will end up in landfill where it won't biodegrade but instead will sit for hundreds or thousands of years.