Stainless steel is one of the most produced materials on earth but is it sustainable and eco-friendly or bad for the environment?
From cutlery and kitchen utensils and water bottles to surgical equipment, building infrastructure and reactor tanks, stainless steel is a remarkable, worldwide phenomenon.
As stainless steel has quite heavy industrial uses, you might automatically assume it’s not very environmentally friendly. You may be surprised. To judge the environmental credentials of stainless steel we need to know how it’s made, what it’s made from and the impact it has at the end of its life.
Let’s get straight it and by the end of this post you’ll be much better informed on whether stainless steel is environmentally friendly or not.
Where is stainless steel sourced? Is this ethical?
To answer this, we need to know just what stainless steel is and what it’s made from.
Stainless steel is a mix (known as an alloy) of a few different metals, mainly iron and chromium (at least 10.5%), plus other materials depending on the grade such as carbon (less than 1%), nickel, molybdenum, aluminium, titanium and others.
The result is an extremely strong, corrosion resistant, non-reactive, durable, recyclable hybrid metal.
Some people ask if stainless steel is a natural resource? Although it is made from natural resources and metals, it does go through an industrial process which isn’t found on earth, so I wouldn’t class it as natural.
The primary material used to make all steel is iron. By mass alone, iron is the most abundant chemical on earth and forms much of the Earth’s inner and outer core. On the earth’s crust, which is where it is extracted from, it’s the fourth most common element after oxygen, silicon and aluminium.
Because iron is highly reactive, it combines with other minerals to form ores. It’s these ores that need to be mined and extracted, where the iron then gets separated from the ore. The three biggest producers of iron ore are China, Australia and Brazil.
How is stainless steel made?
There are two main ways to produce stainless steel:
- From iron ore-based primary raw material
- From recycled material
With the ore-based method, the main inputs for production are iron ore and coal that go into a blast furnace.
When creating stainless steel from recycled material, the main inputs are scrap steel and electricity. The stainless steel is then produced in an Electric Arc Furnace (EAF).
The good news for the environment is that around 80% of all new stainless steel is made from scrap metal and electricity according to the 2018 International Stainless Steel Forum, a non-profit research organisation. With such a high percentage of reuse and repurposing of existing products, it gives a big tick to the sustainability credentials of stainless steel.
The benefits of producing and using stainless steel hasn’t gone unnoticed – the world production of the material this century has more than doubled from 20 million tonnes to over 40 million tonnes.
Steel produced has advanced in recent years and what were once waste products, such as molten slag, now gets sold and used mainly in construction, getting turned into the likes of concrete and asphalt for roads.
Carbon dioxide emissions of stainless steel production
To understand any environmental impact, we need to know about carbon dioxide emissions.
If stainless steel was to be produced solely from raw ore-materials, the CO2 emissions would be around 4.2 tonnes per tonne of stainless steel. Using stainless steel scrap reduces the CO2 needed.
If one tonne of stainless steel is made using 50% scrap metal, carbon dioxide emissions drop below 2 tonnes per tonnes of stainless steel. The more stainless steel that can be recycled and reused to make more stainless steel, the ‘greener’ steel will continue to get.
Using electricity to make stainless steel reduces this even further. One tonne of stainless steel produced with electricity results in CO2 emissions of between 0.28 and 0.49 tonnes.
Since the 1960s, the amount of energy consumption and carbon dioxide emissions from steel production have decreased by more than half. Even better now, the great thing about creating stainless steel using scrap metal and electricity is that the process can be completely fossil-fuel free. Read more on these numbers from worldstainless.org.
What makes stainless steel ‘stainless’?
Many people wonder why stainless steel is indeed stainless?
First of all, there are many different types of steel, all of which are alloys of different metals.
The ‘stainless’ part to this steel means it doesn’t corrode or rust. This is all the more puzzling as the primary material, iron, does rust. Digging in your mental archives back to school, you’ll know that rust forms when iron reacts with oxygen causing iron oxide.
To stop rust forming, you need another material to bind with oxygen before the iron does. This is where chromium comes in.
Stainless steel doesn’t rust because of the chromium added to the mixture, which forms a chromium oxide layer (instead of iron oxide) on the surface of the material. This chromium oxide layer protects the steel underneath and helps give the materials its unique ‘stainless’ properties.
After decades of work on steel all over the world, the handy chromium discovery took place in Sheffield, England, thanks to Harry Brearley. The city is now known as the Steel City.
Stainless steel is also given a three-digit grade, usually imprinted into the product. For example, my stainless steel water bottle is 304 stainless.
Is stainless steel recyclable?
When we consider recycling, the sustainability of stainless steel really starts to come into play.
Yes, stainless steel is fully recyclable.
In fact, it goes further. Stainless steel is infinitely recyclable, meaning it can be recycled over and over again without losing quality. This differs drastically to the likes of plastic and silicone recycling, which degrades in quality.
Globally, it’s predicted that around 85% of stainless steel gets recycled at the end of its life. By all accounts, this is quite a high rate.
Stainless steel recycling in the UK is approximately 96% and in the construction sector itself, the recovery rate is closer to 100%.
The reason for the high rates of recycling is that stainless steel has a high intrinsic value. The raw materials have a high demand themselves, resulting in high capture rates of any stainless steel scrap.
Even better stainless steel recycling system is very efficient and requires no subsidies. The stainless scrap then makes its way to stainless steel production plants where electricity is used (rather than fossil fuels) to create the ‘new’ material. The recycled stainless steel product has just the same properties and qualities as stainless steel made from raw materials.
The fact that very, very little stainless steel ends up in landfill or discarded in the environment means that this aspect of stainless steel is very sustainable.
Is stainless steel biodegradable?
The unique properties of stainless steel means it is unreactive and not an easy place for microbes to live. This also means that stainless steel is not biodegradable.
If left to its own devices in the environment, stainless steel will sit there and persist. This is why recycling is so important.
There’s a good reason it’s used for medical appliances, surgical equipment and stainless steel water bottles and it’s because stainless steel is easily cleaned and sterilised. This makes them perfect for reusing over and over again.
As we now know that stainless steel is 100% recyclable, this should make up for its non-degradable nature.
Is stainless steel environmentally friendly?
Stainless steel that uses scrap metal as part of, or for all of, its content can certainly be considered environmentally friendly.
Although steel made from raw iron ore does require coal, producing stainless steel from scrap and using electricity for energy results in a drastically reduced carbon footprint of the material. It’s now estimated that 80% of all stainless steel production today uses scrap and electricity, which is much better for the environment.
We’ve also seen how many waste materials in the production process, such as slag and even dust, now get reused. Even the water that goes into the process can be filtered and reused.
Stainless steel is environmentally neutral meaning that it doesn’t release any toxins or harmful substances when it comes into contact with water, soil or air.
In the unlikely event that stainless steel does find itself in landfill or worse dumped in a forest or in the ocean, we at least have the knowledge that it won’t result in any toxic run off or cause any further harm to wildlife and the environment aside from being there.
Stainless steel is also a very long-lasting material. This makes it a prime material for reusable items and reduces energy demands during the production of new materials.
With all this in mind, it seems clear to state that stainless steel is environmentally friendly.
The bottom line: Is stainless steel a sustainable material?
As far as worldwide materials go, stainless steel is one of the most sustainable and environmentally friendly. This is particularly true when compared to the likes of plastic and concrete, which are not very eco-friendly at all.
Stainless steel lasts a long time, can be fully recycled, is more often than not made from recycled content and has no detrimental impacts on life, the immediate environment or local ecology. So no, stainless steel is not bad for the environment.
Although stainless steel production in the past has required the use of resource extraction and fossil fuel use, the industry has changed and improved significantly – so much so that an estimated 80% of stainless steel produced today is made using recycled content and electricity.
In my view, all this makes stainless steel a very sustainable material.
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