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All About Cast Iron Sustainability

If you are big on cooking, you probably have a beloved cast iron pot or pan. Cast iron is in high demand because of its many great qualities, such as design flexibility and durability. However, to you, the eco-conscious consumer, the carbon footprint is also an essential consideration. Find out as we look at cast iron sustainability in this article.

Related Read: Granite Cookware.

What is cast iron?

melted iron
Photo by Morteza Mohammadi on Unsplash

Cast iron is a type of iron alloy that contains 2% to 4% of carbon. They create it by melting iron ore in a blast furnace until it is runny and pour it into molds to set. The material is first cast into bars called pigs and then remelted to produce various products.

The metal has specific properties that make it great for castings. In 2018, cast iron comprised 70% of the 110 million tons of all metal cast yearly3.  The material is used to produce products used in construction, engineering, transportation, and many other industries.

Brief background on cast iron

As early as the 6th century BCE, ancient China produced cast iron tools. It came to Europe in 1500 and was introduced to America in 1619. Iron casting innovations have made white iron, gray iron, ductile iron, malleable iron, and other types of cast iron 

Is cast iron sustainable?

cast iron flatlay
Photo by Rayia Soderberg on Unsplash

To determine this, we look at specific elements that come into play throughout the life cycle of the material.

Production pollution

The process of extracting iron ore from the earth’s crust and smelting it results in the release of greenhouse gases. A ton of pig iron produced in a modern blast furnace1 releases up to 1.45 tonnes of CO2e.

Daily foundry activities also release mineral dust, volatile organic compounds, and other particulates into the atmosphere. Pollution can also come from unethical disposal of wastewater and chemicals.

However, cast iron generates lower levels of pollution compared to steel and aluminum.

Energy consumption

The metal manufacturing industry is the second-largest consumer of energy globally. The process of melting the iron ore uses about 55%–80% of the foundry's energy. High energy use is a significant cause for concern because burning fossil fuels is one of the top contributors to global warming2.

A foundry can cut environmental costs by using clean and renewable sources. An improvement in production processes can also cut energy use.

High recyclability

Discarded cast iron can be fully recycled to create new products. The metal can go through infinite recycling loops without losing its structural integrity. Since the problem of inferior properties does not affect recycled cast iron, consumers can enjoy a lower carbon footprint without giving up quality. 

It is also cheaper to recycle scrap cast iron, and that provides an economic incentive for recycling. All kinds of old cast iron can be recycled, from post-consumer scraps to salvaged iron from decades-old buildings. Scrap from other metals, like steel, can be recycled with cast iron4. The foundry industry in the U.S. is so dependent on iron scrap that the recycling rate is up to 90%.

Strength and durability

A long life span is one of the desirable qualities of eco-friendly products. That's because long-lasting products don't have to be replaced often, slowing down the consumption of resources and reducing the environmental impact of production.

Cast iron does not easily rust, even when it's placed outdoors. It is resistant to wear and abrasion. Although it lacks tensile strength, the metal has great load-bearing strength.

With products like kitchen pans, durability depends on how well you maintain them, but you can expect decades of use. In construction, cast iron can outlast even the buildings.

Reusing waste

Foundry sand can be reused many times. When it is no longer useful for casting, they can use it for building and structural filling. Slag is a by-product useful as lightweight concrete aggregate alongside cement production and insulation.

Reusing materials and finding alternative uses for discarded materials is one way cast iron can be sustainable. However, many foundry waste still ends up in landfills because the manufacturers are not actively repurposing it.

Could cast iron be more sustainable?

cast iron on wooden table
Photo by FASTILY on Wikimedia Commons licensed under CC BY-SA 4.0 (Cropped from original)

Sustainable practices in the metal casting industry have improved over the years. However, there are still many opportunities to identify new ways to improve the eco-friendliness of cast iron. For example:

Innovation in smelting methods

The American Foundry Society established the Green Foundry project to document sustainability efforts and award outstanding innovations. They have been able to gather ideas. Initiatives like that help the industry discover more eco-friendly ways to manufacture cast iron.

Local manufacturing 

The government and consumers need to support local manufacturers of cast iron. That would make it easier and more profitable for manufacturers to engage in recycling and other eco practices. It is also easier on the environment to buy locally made cast iron products as that shortens shipping distance significantly.

Other ways include sustainable packaging, better water resources management, etc. The foundry industry can further offset its environmental impact by championing social causes.

Cast Iron vs. Steel 

cast iron with lid
Photo by Davidbena on Wikimedia Commons licensed under CC BY-SA 4.0 (Cropped from original)

Iron's flowability makes it better for casting than steel. Yet, steel has specific properties that make it a preferred material for building construction and other industries. Which is a more sustainable material? Let’s compare them based on the factors below.

Emissions

We obtained iron and steel from iron ore, but steel is a man-made alloy that must undergo extra processes. They both contribute 4% to 7% of carbon emissions globally. Still, the additional process needed to make steel suggests a larger carbon footprint. Also, cast iron has a lower melting point compared to steel.

Durability

Steel has tensile strength and can withstand sudden impact without deforming or breaking. Iron has more significant load-bearing strength, but it is brittle and has low impact resistance. Also, iron is more resistant to rust and wear compared to steel. Those factors determine which of the metals has a longer life span.

Recyclability

Both iron and steel can be recycled many times without diminishing in quality. They're equally matched in this aspect. Steel is one of the most recycled metals in the world, which makes sense since it is the most used.

Conclusion: Cast Iron Sustainability

Cast iron can be recycled indefinitely without diminishing in quality. The metal is also durable and makes up for its initial environmental costs with a long life span. Those qualities, along with other elements like good maintenance and clean power sources, can make it a significantly sustainable material.

1

Abdelshafy, A., Franzen, D., Mohaupt, A., Schüssler, J., Bührig-Polaczek, A., & Walther, G. (2022). A Feasibility Study to Minimize the Carbon Footprint of Cast Iron Production While Maintaining the Technical Requirements - Journal of Sustainable Metallurgy. SpringerLink. 

2

Stefana, E., Cocca, P., Marciano, F., Rossi, D., & Tomasoni, G. (2019). A Review of Energy and Environmental Management Practices in Cast Iron Foundries to Increase Sustainability. MDPI. 

3

Jacques, L., Dawson, S., & Alain, H. (2021). Cast iron: a historical and green material worthy of continuous research. International Journal of Technology: IJ Tech, 12(6), 1123.

4

Tuck. C., (2021). Mineral Commodity Summaries (By U.S. Geological Survey). 

Jen’s a passionate environmentalist and sustainability expert. With a science degree from Babcock University Jen loves applying her research skills to craft editorial that connects with our global changemaker and readership audiences centered around topics including zero waste, sustainability, climate change, and biodiversity.

Elsewhere Jen’s interests include the role that future technology and data have in helping us solve some of the planet’s biggest challenges.

Fact Checked By:
Isabela Sedano, BEng.

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