Steel is one of the world’s most widely used materials, forming the backbone of modern infrastructure, from skyscrapers and bridges to vehicles and appliances. Its strength and versatility make it indispensable to global industry. The tremendous scale of its production raises a fundamental environmental question regarding its long-term sustainability. Is steel a renewable or non-renewable resource? The answer is nuanced, depending on how the material is initially sourced and how it is managed after its service life.
Defining Renewable and Non-Renewable Resources
Natural resources are categorized based on their ability to naturally replenish themselves within a human timeframe. Renewable resources are replenished by nature at a rate equal to or faster than their consumption rate, such as solar energy and wind energy. In contrast, non-renewable resources exist in finite quantities, formed over millions of years through geological processes. These materials are depleted much faster than nature can replace them, limiting their supply. Non-renewable resources include fossil fuels and many mineral ores used in manufacturing.
The Raw Components of Steel
Primary steel production, often using the Basic Oxygen Furnace (BOF) route, relies on several non-renewable inputs. The foundational raw material is iron ore, a mineral extracted from the Earth’s crust. Iron ore is a finite natural resource, meaning its reserves are limited and depleted through continuous mining.
Another indispensable input is coking coal, a non-renewable fossil fuel. Coking coal is converted into coke, which provides intense heat and acts as a chemical reducing agent in the blast furnace to strip oxygen from the iron ore. Since fossil fuels are consumed and converted into emissions during the process, they are definitively classified as non-renewable. Limestone is also added as a flux to draw out impurities. The reliance on these mined mineral ores and fossil fuels means primary steel production is fundamentally dependent on non-renewable resources.
Steel’s Role in the Circular Economy
The classification of steel becomes complex when considering its behavior at the end of its useful life, due to its exceptional recyclability. Steel is considered a permanent material because it can be recycled repeatedly without any degradation or loss of its inherent strength or properties. This infinite potential for reuse positions steel as a highly sustainable material within a circular economy model.
The steel industry uses the primary production route (BOF) and the secondary route, often utilizing the Electric Arc Furnace (EAF). The EAF method allows for the production of new steel using almost 100% scrap material, significantly reducing the need for virgin iron ore and coking coal. This secondary process requires substantially less energy, often up to 60% less, compared to making steel from raw materials.
Steel is the world’s most recycled material by tonnage, a testament to its value and magnetic properties which make it easy to recover. Current recovery rates for steel are very high, averaging around 85% across various product markets. In 2021 alone, approximately 680 million tonnes of steel were recycled worldwide, demonstrating the massive scale of this circularity. While the material originates from non-renewable sources, its unique ability to be infinitely reused in a closed-loop system mitigates the environmental impact associated with finite resource depletion.