Role of steel scrap sorting for sustainable steel production; advantages and disadvantages compared to blast-furnace plus basic oxygen-converter-based steel production

Scrap sorting is a crucial process and precondition in the recycling of steel that significantly enhances both the quality of recycled materials and the future enhanced sustainability of steel production. With this, scrap sorting plays a pivotal role in enhancing the sustainability of steel production by facilitating the efficient recycling of steel materials. This process involves the separation of scrap metals into various categories based on their composition, type, and quality, ensuring that only suitable materials are used in the production of new steel products. 

By separating scrap metals into various categories based on their composition and quality, this practice ensures that only the most suitable steel scraps types are utilized in creating new steel products. The importance of scrap sorting lies in its ability to maintain high standards in recycled steel production, which not only reduces energy consumption and greenhouse gas emissions compared to conventional steel manufacturing but also supports the circular economy by maximizing resource reuse.

The advantages of scrap sorting are multifaceted. Primarily, it leads to much lower energy requirements during steel production, as melting sorted scrap is less energy-intensive than working with virgin raw materials where the iron must first be extracted from ores. Additionally, effective sorting minimizes the environmental impact associated with mining and processing these resources, contributing to reduced ecological footprints.
However, challenges persist, including the complexity of the sorting process and variability in scrap quality, which can introduce contaminants and require additional processing to meet industry standards.

Another aspect are supply chain challenges: the scrap-based steel industry is influenced by the volatility of scrap supply and demand. This can lead to fluctuations in inventory levels and unpredictability in sourcing strategies, potentially affecting production schedules and operational efficiency

Technological advancements in scrap sorting, such as automated sorting systems and AI-driven analytics, have improved efficiency and accuracy, thereby enhancing the quality of recycled steel and reducing operational costs.
Despite these innovations, the initial investment required for advanced sorting technologies can pose financial barriers, particularly for smaller manufacturers, potentially deterring widespread adoption of sustainable practices.
Overall, while scrap sorting plays a pivotal role in promoting sustainable steel production and reducing environmental impacts, it is essential to navigate the associated challenges, including quality variability and the financial implications of adopting new technologies, to fully realize its benefits in the steel recycling industry.

The steel sector causes approximately 30% of all global industrial CO2 emissions in producing 1.9 billion tonnes of steel per year. On a global average, current production technologies release nearly 2 t of CO2 per tonne of steel produced. The majority comes from blast furnaces (delivering a near-eutectic Fe–C alloy called pig iron) and oxygen converters (producing steel from
pig iron), a coupled route that accounts for approximately 80% of global steel production.
Therefore, other primary synthesis methods are being investigated to mitigate CO2 emissions in this sector. A process with a high technology readiness level is direct reduction in shaft reactors. In this approach, centimeter-sized polycrystalline sintered oxide pellets are exposed to a reducing gas (today, mostly H2 plus CO syngas mixtures made from methane), producing 93–98% metalized sponge iron. This technology is in operation worldwide but accounts for a small fraction, approximately 6–7%, of global steel production. Replacing the currently used fossil reductants with green hydrogen in direct reduction reactors is one of the most promising sustainable pathways, capable of at least partially replacing blast furnace production. This approach could po-
tentially drastically reduce CO2 emissions in the steel sector, provided the hydrogen comes from sustainable sources. Other green steel production methods under development, but not yet at the same technology readiness level, are hydrogen plasma-based smelting reduction methods, ammonia-based direct reduction, and cathodic deposition of iron from fused-salt electrolysis of iron oxide.
A problem that all these alternative technologies share is the long transition time required to realize their expected CO2 mitigation, probably up to 1–3 decades on a global scale. This has several reasons.The necessary research, as well as the construction of industrial plants, will take several decades on a scale as massive as global steel production. The transition from the blast furnace–basic oxygen converter (BF–BOF) route to hydrogen-based direct reduction (which is the likely future workhorse technology) will require intensive research, tens of billions
of euros of investments, and time to build and optimize these new facilities. Furthermore, at least 250–300 million t of sustainably produced hydrogen will be required per year, an amount that is unlikely to be available in the next few years due to insufficient electrolysis capacity and renewable energy. The currently available, sustainably produced amount of hydrogen available is three-to-four orders of magnitude below the demand from the steel sector alone.

This means that CO2 emissions from the steel sector must be reduced as soon as possible, not 20 or 30 years from now, because CO2 remains in the atmosphere for centuries once released. Therefore, increasing the utilization of scrap steel for secondary synthesis, that is, recycling, is the fastest and most disruptive way to at least partially decarbonize the steel sector in the coming years. With a current fraction of about 28% of global steel production, scrap melting is a long-established standard recycling method and is expected to grow rapidly in the next few years if (a) enough electric arc furnaces (EAFs) are installed, (b) the energy used to run them increasingly comes from sustainable power generation, and (c) the scrap market grows accordingly. All three criteria are in principle within reach such that secondary synthesis has a realistic chance of providing a rapid route to decarbonizing up to a 30% share of the steel sector, with the potential to grow up to 60–70% by 2040. Recycling through melting scrap in EAFs has the main advantage of directly using electricity, which should ideally come from renewable sources, for heat generation. This fact alone reduces the high energy losses associated with heating air, as in conventional furnaces. 

According to estimates by the World Steel Association, recycling 1 t of steel scrap saves around ...

• 1.4–1.5 t of iron ore,
• 0.5–0.6 t of coal, and 
• 40–75% of the energy required for primary steel production.

With 1 kg of steel produced from steel scrap instead of through the BF–BOF

route, this translates to end-of-life savings of approximately ...

• 1.5 kg of CO2 emissions,
• 13.4 MJ of primary energy, and
• 1.4 kg of iron ore,

( corresponding to reductions of 73%, 64%, and 90%, respectively).

This means that the potential reduction in CO2 emissions is enormous when turning from primary to secondary synthesis: Using 1 t of scrap in steel production instead of pig iron from the blast furnace can reduce CO2 emissions by around 58–64%.
The exact reduction depends on factors such as the scrap composition, production process, EAF electrodes (inert or graphite), and energy sources used. The last point is particularly important: In the production of steel from scrap via the EAF route, the CO2 footprint of the supplied energy plays a crucial role. This means that CO2 reduction via the EAF route depends on the CO2 foot-
print of the used electrical energy. The International Energy Agency predicts a CO2 factor for the grid in Europe of 80 g/kWh by 2050, which can lead to a CO2 reduction of 289 kg/t of crude steel for this route or a decrease of 57% in 2050 compared with 1990. If the supplied energy is provided by CO2-neutral fuels or CO2-free electrical energy,CO2 emissions can even be reduced by up to 60 kg/t of crude steel, which is still unavoidably generated by the consumption of graphite electrodes and the use of additives and alloying elements. This corresponds to a CO2 reduction of 91% for the scrap-based EAF route compared with 1990.

Scrap sorting is a critical step in the recycling process of steel, which significantly impacts both the quality of the recycled material and the overall sustainability of steel production. This process involves separating scrap metals into various categories based on their composition, type, and quality, ensuring that only suitable materials are used in the production of new steel products. The sorting of scrap metals is essential for maintaining high standards in recycled steel production, which, in turn, offers several advantages over conventional steel manufacturing.
Scrap sorting enhances the purity of the recycled materials. High-quality scrap is less likely to introduce contaminants, which can negatively affect the properties of the final steel product. The separation of ferrous metals, which contain iron and are magnetic, from non-ferrous metals, which do not contain iron and are non-magnetic, is a fundamental aspect of the sorting process. Techniques such as magnetic sorting, manual sorting, and advanced methods like X-ray fluorescence (XRF) and laser-induced breakdown spectroscopy (LIBS) have been developed to improve the efficiency and accuracy of sorting operations.
Modern scrap sorting facilities utilize a combination of manual labor and automated technologies to achieve precise material classification. Electromagnetic separators and optical scanners are frequently employed to enhance sorting accuracy and speed, allowing facilities to ensure that only the highest quality scrap is processed further. These advancements not only improve the quality of the recycled steel but also reduce the operational costs associated with scrap processing.

Modern scrap sorting facilities utilize a combination of manual labor and automated technologies to achieve precise material classification. These advancements include:

• Electromagnetic separators
• Optical scanners
• X-ray fluorescence (XRF) analysis
• Laser-induced breakdown spectroscopy (LIBS)

These technologies enhance sorting accuracy and speed, improving the quality of recycled steel and reducing operational costs

One of the primary advantages of scrap sorting is the reduction in energy consumption during steel production. Recycling steel from sorted scrap requires significantly less energy compared to producing steel from virgin raw materials, as the melting point of scrap steel is lower than that of iron ore. Additionally, recycling helps to decrease greenhouse gas emissions associated with steel production, making it a more sustainable option for the environment. Furthermore, effective scrap sorting contributes to the circular economy by ensuring that valuable materials are reused rather than discarded. This practice reduces the demand for raw materials, thereby minimizing the environmental impact associated with mining and processing these resources.

Realizing higher fractions of secondary steelmaking (i.e. made from scrap) is gaining momentum as a sustainable alternative to primary steel production. Steel production from scrap is well established for long products (rails, bars, wire), but there are two main challenges. First, there is not sufficient scrap available to satisfy market needs. Today, only one-third of global steel demand can be met by secondary metallurgy using scrap since many steel products have a lifetime of several decades. However, scrap availability will increase to about two-thirds of total demand by 2050 such that this sector will grow massively in the next decades. Second, scrap is often too contaminated to produce high-performance sheet steels. This is a serious obstacle because advanced products demand explicit low-tolerance specifications for safety-critical and high-strength steels, such as for electric vehicles, energy conversion and grids, high-speed trains, sustainable buildings, and infrastructure. Therefore, we study in our work the metallurgical and microstructural challenges and opportunities for producing high-performance sheet steels via secondary synthesis. Focus is placed on the thermodynamic, kinetic, chemical, and microstructural fundamentals as well as the effects of scrap-related impurities on steel properties.

Here scrap sorting becomes essential as outlined above, yet, despite its many benefits, scrap sorting is not without challenges. The complexity of the sorting process can lead to increased operational costs, particularly when advanced sorting technologies are utilized. Additionally, the quality of the scrap collected can vary significantly, particularly when dealing with old scrap, which may be contaminated or mixed with other materials. Moreover, the logistics of transporting sorted scrap to processing facilities can pose a challenge, requiring efficient infrastructure and strategic planning to handle bulk quantities effectively.

• Emission Reduction: EAF-based recycling reduces greenhouse gas emissions by approximately 50% compared to traditional methods.
• Energy Savings: Although exact figures are not provided, the energy required to melt scrap steel is significantly lower than that needed to process iron ore, potentially resulting in energy savings of 60-80% based on industry standards.
• Resource Conservation: Steel recycling conserves substantial amounts of iron ore, coal, and limestone, though specific quantities are not mentioned in the text.
• Economic Impact: The steel recycling industry generates numerous jobs, but exact figures are not provided in the given information.

Economic Benefits
Scrap sorting plays a critical role in enhancing the economic viability of steel recycling. By effectively sorting and separating scrap materials based on their type and quality, recycling companies can lower production costs. Recycled steel requires significantly less energy and raw materials compared to conventional steel production, which relies heavily on mining and processing virgin materials. Furthermore, the steel recycling industry generates jobs across various stages, including collection, sorting, and processing, thereby contributing to local economies and promoting a circular economy.

Environmental Impact
One of the primary advantages of scrap sorting is its substantial positive impact on the environment. By recycling steel, the industry conserves natural resources such as iron ore, coal, and limestone, thereby reducing the ecological footprint associated with their extraction and processing. Efficient sorting processes ensure that contaminants are minimized, leading to higher-quality recycled steel. The use of technologies such as electromagnetic separators and sensor-based sorting systems enhances purity by effectively removing unwanted elements like copper and tin. This is crucial as recycling steel in electric arc furnaces (EAFs) results in 50% lower greenhouse gas emissions compared to traditional methods, making steel recycling a vital strategy in combating climate change.

Resource Efficiency
Scrap sorting facilitates resource efficiency by enabling the reuse of a wide range of steel grades and alloys. The ability to match scrap steel with specific steel grades based on the properties of the alloys involved allows for the production of tailored products that meet industry standards. As different carbon content levels significantly affect the hardness, strength, and weldability of the final steel products, precise sorting is essential for achieving desired characteristics in the recycled material.

Support for a Circular Economy
The practice of scrap sorting supports the principles of a circular economy by promoting the continuous reuse and recycling of materials. This approach minimizes waste and reduces the need for new raw materials, which in turn mitigates the environmental impact associated with their production. Moreover, the integration of advanced technologies in sorting processes fosters higher recycling rates, enabling a more sustainable steel production cycle that aligns with global sustainability goals.

Technological Advancements
Advancements in sorting technologies have significantly enhanced the efficiency of the steel recycling process. Techniques such as X-ray fluorescence (XRF) analysis allow for rapid and accurate identification of scrap metal composition, which is vital for quality control. Additionally, the automation of sorting processes improves productivity and safety in recycling facilities, further optimizing the overall operation of steel recycling plants.

The use of scrap sorting in steel production, while offering numerous advantages, also presents several disadvantages when compared to traditional methods of steel manufacturing.

Complexity of Scrap Sorting
One significant disadvantage is the complexity involved in sorting and preparing scrap materials. The process requires advanced technologies and systems to effectively separate contaminants and unwanted elements from high-quality scrap. The initial costs for high-precision sorting equipment, which may include magnets, advanced sensors, and artificial intelligence algorithms, can be considerable.
 Additionally, the maintenance of such sophisticated systems poses ongoing expenses that may not be as prominent in conventional steel production processes.

Quality Variability
Another challenge is the inherent variability in scrap quality. Unlike raw materials used in conventional steel production, which are sourced from controlled environments, scrap can contain unpredictable amounts of contaminants and residual materials. Steel producers often rely on scrap suppliers for accurate information about the quality and composition of their materials, which can lead to inconsistencies and the need for further processing to meet desired specifications. This reliance on external suppliers makes the steel production process more vulnerable to fluctuations in scrap quality.

Environmental and Safety Risks
The storage and management of unwanted materials from scrap sorting also introduce environmental and safety concerns. Companies must implement careful handling procedures to manage contaminants appropriately, which can require additional resources and regulatory compliance. Furthermore, the risks associated with hazardous materials in scrap can complicate operations and necessitate more stringent safety protocols compared to traditional production methods.

Supply Chain Challenges
Supply chain management is another area where scrap sorting can be less efficient. While AI and other technologies can enhance logistics in the scrap industry, the process is still influenced by the volatility of scrap supply and demand. This can lead to fluctuations in inventory levels and unpredictability in sourcing strategies. As a result, producers may face challenges in maintaining a steady supply of high-quality scrap, which can affect production schedules and operational efficiency.

Dependence on Industrial Activity
The availability of new scrap, generated from manufacturing activities, is also subject to the cyclical nature of industrial output. In times of low economic activity, the generation of new scrap can diminish, leading to potential shortages. This dependence on industrial activity contrasts with the more stable supply of raw materials typically used in conventional steelmaking.

Advantages of Scrap Sorting in Sustainable Steel Production
Scrap sorting plays a crucial role in enhancing the sustainability of steel production. One of the primary advantages is the significant reduction in raw material costs, as recycling scrap steel often proves more economical than sourcing virgin materials. This cost-effectiveness is complemented by lower energy requirements, leading to decreased carbon emissions during production. The optimized blending of scrap with pure elements results in a minimized total blending cost, demonstrating the economic benefits associated with using recycled materials. Moreover, scrap sorting contributes to resource conservation and waste reduction. By effectively recycling steel, industries can mitigate the environmental impacts associated with mining and processing virgin materials, which are energy-intensive processes. The incorporation of carbon penalties for high-carbon content scrap within optimization models further encourages the use of cleaner, lower-emission materials, aligning with global efforts to reduce carbon footprints and comply with regulatory frameworks like the European Green Deal.

Disadvantages of Scrap Sorting in Sustainable Steel Production
Despite its numerous advantages, scrap sorting also presents certain challenges. One significant drawback is the variability in the quality and composition of scrap steel, which can lead to inconsistencies in the final product. This variability requires additional processing and quality control measures to ensure that the recycled material meets industry standards. 
The optimization models must also account for potential losses of valuable elements during the melting process, complicating the recycling efforts.
Additionally, the initial investment in advanced sorting technologies can be substantial. Industries may face upfront costs for the necessary equipment and training to implement effective scrap sorting practices. These costs can deter smaller manufacturers from adopting sustainable practices, potentially leading to a reliance on conventional steel production methods. As regulatory pressures increase and the market shifts towards sustainability, the challenge remains to balance the economic feasibility of scrap sorting with the need for consistent quality in steel production.

Modern Steel Scrap Sorting Facilities
Modern scrap sorting facilities have adopted advanced technologies to enhance the efficiency and accuracy of material classification. These facilities combine manual labor with automated technologies, including electromagnetic separators and optical scanners, to ensure high-quality sorting of scrap metal. Traditional methods of sorting, such as manual techniques and basic magnets, are increasingly being replaced by sophisticated systems that utilize X-ray Fluorescence (XRF) and other high-precision equipment. This technological shift not only increases efficiency but also enhances the quality of recycled materials, making them suitable for various industrial applications.

Predictive Analytics and AI
In the context of sorting scrap metal, artificial intelligence (AI) and machine learning technologies are transforming the industry. AI-powered systems can analyze and sort different types of metals with exceptional accuracy, reducing the reliance on manual labor and minimizing errors. These systems can identify specific metal types and alloys, thereby improving the overall efficiency of the recycling process. By ensuring that only high-quality materials enter the supply chain, businesses can better meet the stringent quality standards required by manufacturers.

Sustainable Practices and Business Responsibilities
Adopting sustainable practices is essential for businesses in the scrap metal industry. Companies are increasingly recognizing the need to implement efficient recycling processes and establish robust waste management systems. By prioritizing sustainability, businesses contribute to the circular economy, thereby reducing the environmental impact associated with steel production and consumption. Individual consumers also play a critical role by responsibly disposing of scrap metal and supporting businesses that engage in sustainable practices. These case studies illustrate how sorting practices in the scrap metal industry not only enhance operational efficiency but also contribute to broader environmental and economic sustainability goals. As the industry continues to evolve, the integration of advanced technologies and sustainable practices will be key to addressing the challenges of resource scarcity and pollution.