One Product’s Waste is Another Product’s Input: Steel’s Role in a Circular Economy

The world is quickly realizing that our current methods of production and consumption will not be sustainable long term. Many rivers, oceans, and even remote regions are becoming littered with waste from a linear economy. Our current societal drive for overconsumption and convenience has fostered the linear production and disposal system that has global consequences at all stages of most products’ life cycles. From harmful extraction techniques to single-use disposable packaging, these practices are slowly flooding the planet with harmful byproducts.

Many propose that a solution to this problem will be the transition from a linear production model to one that is circular, incorporating the 3R’s; Reduce, Reuse, and Recycle. Plastic, however, may not have a place within such a model as over 80% of plastics cannot be recycled or reused, so a more durable and sustainable material is needed to fulfill a circular supply chain. One such material is metal, as many metals can be infinitely recycled while maintaining their structural integrity as they can be made into a completely new product at the end of another’s life cycle.

The Life Cycle of Steel

Of the roughly 3.25 Billion tons of metal/ore mined in 2021, 3 billion tonnes (94%) is iron ore, while industrial metals (200M) and tech/precious metals (1M) make up the remaining 6%1. Metals may play a crucial role in the transition to a circular economy as many of them are infinitely recyclable with their high value making recycling economically feasible. However, when considering life cycle thinking (LCT) regarding the role of any product, technology or process, we need to bear holism in mind for all stages of the production process, energy inputs, raw material sourcing, waste byproducts, etc.

Steel (iron ore) will have a vital role to play in the circular economy as it is by far the most used metal by weight in the economy today and because of its physical properties. It is primarily used for construction, mechanical engineering, and automotive purposes. Looking at the life cycle of steel, there are many aspects of its production process, distribution, and collection that must be analyzed and refined to create a more sustainable material overall.

The life cycle of steel begins at the point of extraction where it is drilled or blasted out of the earth in mines around the world. The top producers of iron ore (Australia, Brazil, China, India and Russia) produce a combined 1,965 tonnes of ore, which is 82.1% of the total global production2. At this stage, the main considerations are energy consumption, C02 production, and habitat destruction. Dr. Ing. De Minas wrote a short paper describing the energy impact index (EII) and how to use it when considering the impacts and sustainability of iron mining. They speak to how the extraction process has been made significantly more efficient in recent years and continues to improve and stress the importance of the iron content (or waste/ore ratio) on energy needs and the effects further down the production process3. Additionally, there is the highly recyclable nature of steel where today 85-90% of steel products are recovered to create new steel. Recycling rates depend on end product steel goods4 and the processing method used, where a blast furnace (BF) method can only use up to 35% scrap while an electric arc furnace (EAF) can be up to 100% scrap5.

The various methods of processing require different inputs as well as different outputs other than the steel. The BF method requires iron ore (1,400kg), coal (800kg), limestone (300kg), and steel scrap (120 kg) as inputs, making 1000 crude steel, and about 70% of the world’s steel is produced this way. The EAF method requires a typical mix of steel scrap (880kg), iron ore (300kg), coal (16kg), and limestone (64kg) as inputs, making 1000 kg crude steel, and the remaining 30% of the world’s supply is made this way5. Both these methods create by-products such as C02, slags, tar and benzene which the industry is working to find markets for, as well as ensuring upward of 96% conversion of raw materials (iron ore) to steel, with the goal of 100%. However, using recycled steel can amount to a great deal of energy and raw material savings with over 1,400 kg of iron ore, 740 kg of coal, and 120 kg of limestone are saved for every 1,000 kg of steel scrap made into new steel6. Compared to producing steel from virgin materials, the production of new steel from recycled materials uses 60% less energy, reducing CO2 emissions by 58%7.

Longevity Plays a Part in Sustainability

The end of the cycle is one of the strongest contributors to the sustainability of steel as many steel goods have life spans that exceed 20 years. Almost 75% of all steel products ever made, including bridges, buildings and heavy machinery, are still in use today which demonstrates the incredible durability of the material5. The longevity of steel also means that we have less need for the extraction and processing stages as there will be less frequent replacement of capital. This also means that these end products will take time to re-enter the life cycle as a ‘raw material’ thus requiring additional extraction of iron ore to meet the demand for steel products. Therein lies the main obstacle to the full circular economy model related to steel/metal as demand will, at least for now, always be higher than the recyclable material available, meaning metal cannot be truly circular.

The remaining 6% of precious metals/tech (lithium, cobalt, indium, etc.) or industrial metals (aluminum, copper, manganese, etc.) are also very important in today’s circular economy as they are used in items many use every day, including phones, TV’s, solar panels, wiring, etc. Many of these natural resources are much rarer and are becoming more in demand as technology advances ever faster. This is both good and bad. While the limited quantities of these metals will make extraction both expensive and time-consuming, the benefits come with the high economic value of such metals which make things like ‘urban mining’8 feasible.

Techniques like urban mining and methods such as life cycle thinking are crucial to the circular economy, providing new ways of turning waste into useful inputs and ensuring production processes are sustainable at all stages. While new innovative ways of consuming goods, producing energy, and generating growth are crucial for sustained human development, we must take into account all inputs and outputs, emphasizing circular supply chains wherever possible, to achieve true sustainability. 












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