Reader Question: Is Cast Iron Truly Eco-Friendly?

We love getting comments and questions from Leaf Score readers, including this one about the sustainability of cast iron:

I am surprised you give cast iron 5 leaves. It takes an incredible amount of energy to create, it is not very biodegradable, and while technically recyclable, again requires huge amounts of energy to recycle. Isn’t there anything kinder to the environment than cast iron?

Teresa

So, what’s the verdict? Is cast iron actually sustainable or is this the ultimate greenwashed cookware? For that, let’s dig into the lifecycle of cast iron.

Cast Iron Pan Life Cycle Analysis

Cast iron pans date back to the sixth century in China. One of our favorite brands, Lodge (see our review), has been making these pans since 1896! 

I doubt that your cast iron pan is quite that old, but it was probably produced using very similar materials and methods. The difference is that modern cast iron production:

• Uses less energy
• Requires fewer raw materials
• Reuses byproducts to reduce waste
• Is far less polluting.

Let’s dig into the lifecycle of a cast iron pan, from materials to manufacturing, distribution and use, through to end of life recycling and disposal.

What materials go into a cast iron pan?

These are the basic materials you need to make a cast iron pan:

• Pig Iron: A crude iron form, primarily sourced from blast furnaces (or electric arc furnaces) used to make steel and wrought iron. So called because some ingots of crude iron look like piglets!
• Scrap Steel: Old steel from items like cars and appliances is recycled and mixed with excess scrap steel overproduced by industry.
• Recycled Cast Iron: Imperfect cast iron cookware is melted and remade into cast iron pans

As you can see, right at the materials level, cast iron starts to look sustainably made. The use of reclaimed and recycled materials helps to cut waste and use resources efficiently. It also makes for more budget-friendly cookware and helps prevent valuable steel and other materials going to landfill.

Now we know what it’s made from, let’s look at how cast iron cookware is made. 

Cast iron manufacturing – more sustainable than you might think

The manufacturing process for cast iron involves the following key steps:

1. Raw materials are melted together 
2. Vermiculite is used to bond to slag to remove impurities
3. The liquid iron is poured into sand molds for casting
4. Once cooled, the sand is shaken off the cast iron pans 
5. Traditionally, manufacturers then blast the pan with fine steel to remove residual sand and polish the surface
6. Water and soap are used to clean the pans before they’re packed for shipping.

Vermiculite is a hydrated magnesium aluminum silicate mineral which is readily available all over the world.

The sand molds are made from sand typically found in foundries themselves, making it locally sourced. The sand is usually filtered and reused alongside a small amount of fresh sand to make more molds after each casting.

The sustainability of cast iron pan manufacturing and materials

One of the reasons I favor cast iron produced in America is because most U.S. foundries now use an electric arc furnace to melt metals. These furnaces still produce waste but are much more environmentally friendly than a traditional blast furnace.

The basic steps in producing cast iron haven’t changed much over the centuries: heat up metal, pour into molds, let cool.

While the process is a bit more streamlined than before the 1950s, the biggest changes can be seen in waste management. Overall, modern cast iron production creates less waste and reuses more of that waste.

In modern cast iron production, byproducts have found a variety of uses:

1. Slag is used as raw material to make other items, including aggregate in the cement industry and for building roads, making insulation, and for fertilizers. 
2. Carbon monoxide is no longer released into the atmosphere and is instead used to increase furnace efficiency
3. Electric arc furnace (EAF) dust is captured for use in the steel making process and in making zinc oxide and other iron products.

Cast iron pan – the environmental impact of manufacturing and distribution 

For some products, the biggest environmental impact is during manufacture or disposal. For others, the biggest impact is from distribution or the use phase of their lifecycle. 

There’s no getting around the fact that cast iron pans require a lot of energy to produce. They are also very heavy. This means there’s a considerable amount of carbon emissions associated with shipping this cookware around the globe.

The nice thing about cast iron, though, is that it’s not delicate. This means cookware brands can ship it in simple, sturdy, cardboard without any fussy, synthetic padding. Think about how much packaging (and single-use plastic) most modern cookware comes with to protect delicate ceramic or ceramic coated or non-stick pans.

The best way to cut the footprint of cast iron is to buy cookware made close to where you live. If you live in the U.S., buying cast iron made in the U.S. helps reduce the impact of both the manufacturing and the distribution stages of the pan’s lifecycle.

Use phase impact for cast iron pans

Using a cast iron pan can be very efficient! These pans take a while to heat up on a traditional electric or gas stove but retain heat really well. That means they’re often more efficient to cook with overall.

You can also use cast iron pans with induction stovetops, which are the most energy efficient cooktops by far. 

Because cast iron pots and pans are oven safe, you can also replace some bakeware and cookware with a single cast iron pot or skillet. This helps reduce kitchen clutter and resource use overall.

Finally, cast iron can last for many generations if properly cared for. That means the total use stage impact of this cookware is far lower than for pans that only last a few years. For some non-stick pans, you’re lucky to get a year of use before the coating deteriorates and the pan is no longer safe or efficient.

Can you recycle a cast iron pan?

While most cast iron pans are virtually indestructible, accidents happen. A little bit of rust is easy enough to clean off before seasoning the pan again. Significant rust can lead to cracks in the pan, though. 

When a cast iron pan reaches end of life, don’t put it in the trash. Cast iron is a valuable resource and can easily be cut or melted down to make into new products – maybe even a new pan! 

Many cities have a dedicated waste management system to recover cast iron, steel, and other scrap metal. Recovering a metric ton of cast iron scrap can conserve:

• More than 1,000 kilograms of iron ore
• 580 kg of coal,
• 50 kg of limestone. 

Cast iron can sometimes be cut for reuse. Most often, though, recycling depots collect scrap metal and send it to a nearby foundry for use as a raw material in making new iron products.

Final thoughts on the sustainability of cast iron cookware

We’ve gone on quite the journey with cast iron. From resource extraction to recycling, cast iron pans are surprisingly green. They’re also:

• Timeless
• Cost-effective
• User-friendly (no need to worry about scratching delicate coatings)
• Induction friendly
• Recycled and recyclable.

I didn’t inherit any cast iron pans, but I plan to pass on my cast iron collection to the next generation, or the one after, when I’m older. Overall, the production cycle of cast iron is a model of sustainability and the benefits of keeping things simple. Cast iron pans demonstrate how traditional products can teach us a lot about building a greener future.

See: The pros and cons of cast iron cookware.