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Steel repair, reuse, recycling and downcycling
Steel is a metal that is an alloy of iron and carbon. It is produced worldwide and, along with cement, forms the foundation of the global construction and engineering industry. Steel is used for a variety of applications, ranging from construction to the medical sector [i].
Europe is home to some of the largest and oldest steel producers in the world. In 2020, the EU 28 was one of the largest crude steel-producing regions in the world [ii]. Out of all of the EU member states in 2021, Germany was the member state that produced the most steel [iii, iv].
How can we reach a more efficient steel sector?
Over the course of its lifetime, steel corrodes and its physical characteristics change due to the ‘wear and tear’ during its use. The damage to the steel will also depend on the environment it is in (e.g., exposure to saltwater or seismic waves). Through exposure to these external factors and frequent use, the steel loses its structural integrity over time.
Repairing steel structures, if that is a possibility , can prolong the lifetime of the material and prevent demolition and scrap waste.
Steel can be repaired by welding pieces of it to patch up any breaks in the structure. If there are some smaller cracks in the steel, epoxy can be used to fill in the cracked sections. Rust removers or protective coating can be applied to the steel to avoid corrosion [v].
After a building has reached the end of its functional lifetime, some steel components embedded in it might be suitable for reuse. After a steel component has been selected for reuse, it needs to be tested and examined to make sure it is suitable for its new use [vi]. Steel components that have been exposed to extreme damage or loads cannot be reused due to their irreparable damage that would compromise their performance.
The potential for the reuse of steel components depends on conditions such as the proximity to the construction location, re-certification and additional costs.
The main obstacles to the reuse of steel are difficulties in sourcing the material (i.e., the mismatch between demolition and construction), increased costs and re-certification issues [vii].
3. Recycling and downcycling
Steel recycling, also known as secondary steelmaking, is the source of approximately 50% of total EU steel production [viii]. Europe is also the largest exporter of steel scrap in the world; in 2020, the EU exported 22.6 million tonnes of steel. 90% of all of the stainless steel in Europe at the end of its life, is collected and recycled into new products [ix].
The key raw materials needed for steel recycling are waste steel (also referred to as scrap) and iron, the need for which depends on the availability and quality of the steel scrap [x]. Electricity is usually used as a power source in the process and is often complemented with other sources of energy and carbon such as natural gas or coal.
In an Electric Arc Furnace (EAF), at very high temperatures between 1800°C – 3000°C the steel scrap is melted together with iron and some other materials to produce liquid steel. The liquid steel then goes into a metallurgy treatment process. The steel is then cast and formed into the desired shape before it is distributed.
Today, approximately 50% of total EU steel production comes from recycling. While its share can be increased, impurities in scrap steel must be diluted with new primary steel to maintain quality.
However, while metals are infinitely recyclable in principle, incomplete separation, complex product design and inadequate recycling technologies make the recycling process increasingly difficult [xi], [xii], [xiii]. Steel is often alloyed with other metals and materials; with each cycle, impurities such as copper and tin are difficult to remove and accumulate in recycled steel [xiv], [xv]. According to some studies, the increased use of scrap material has caused a sharp rise in impurities in steel [xvi], resulting in lower quality recycled steel products.
As with any form of recycling, ‘’the more intricate the product and the more diverse the materials it uses, the better it is likely to perform, but the more difficult it is to recycle so as to preserve the resources that were essential to making it work in the first place’’ [xii]. Such issues are an important challenge to the recycling of steel and need to be overcome with improved sorting of metal waste and innovations in the purification and removal of contaminating materials.
How do circularity measures impact emissions in the steel sector?
Steel reuse can potentially reduce emissions by meeting the demand for some steel applications in society that would otherwise be met with primary steel.
Nevertheless, for recycling, the quality of the metal produced still hinges on the primary production of steel, which needs to be decarbonised through other means. Higher rates of steel recycling will not always result in less primary steel production, making this substitution effect difficult to measure.
The emissions that can be cut through steel recycling also depend on the source of energy that is used to power the electric arc furnace. The purity of the pig or sponge iron used in production also plays a role in the climate footprint of the recycling process, as well as the amount of scrap that can be used, depending on the desired grade of steel.
Producing steel through secondary steel making produces about 0.455 tonne CO2/t of steel, whereas the traditional blast furnace primary steel making route emits 1.7-1.9 CO2/t of steel [vi].
However, while secondary steel can replace some primary steel, there are growing obstacles to closing the loop. Using recycled steel tends to introduce impurities into the steel which accumulate and are then difficult to remove [xvii].
The accumulation of impurities can be improved by better sorting, simpler product design and the development of new technologies for the purification of recycled steel.
According to some scenarios, the current scrap recovery and recycling patterns could lead to a 50% loss of usable steel stock by 2100 [xviii]; it is important to slow this loss of materials through better sorting and recycling practices.
Key measures and enablers needed
- In addition to circularity measures, the primary production of steel and iron needs to be decarbonised.
- Steel products need to be designed for reuse or re-manufacturing in order to retain the most value and increase the lifespan of the material. By extending the product lifetimes through maintenance, repair, restoration and reuse, the loss of high-quality steel can be slowed.
- Current loss rates are caused by current sorting and recovery practices, trade patterns and product lifetimes. All of these elements need to be reassessed to enable more efficient use of steel.
- Recycling rates can be improved by establishing the right infrastructure. Increased collection and pre-sorting of post-consumer and industrial waste are significant infrastructural elements needed for steel recycling.
- Technical and economically viable processing streams are key for high collection rates. Successful recycling plants and electric arc furnaces need high volumes of high-quality steel scrap in order to meet initial investments and produce good quality steel. To reach that goal, governments and public authorities should ensure a good collection and pre-sorting system [xix].
[i]World Steel Association. About steel. Available at: https://www.worldsteel.org/about-steel.html
[ii] Statista. 2021. Crude steel production in major producing countries and regions in 2020. Available at: https://www.statista.com/statistics/267263/world-crude-steel-production-by-region/
[iii] Statista.2021a. Steel Production by Country 2021. Available at: https://worldpopulationreview.com/country-rankings/steel-production-by-country
[iv] Bureau of International Recycling. WORLD STEEL RECYCLING IN FIGURES 2016 – 2020 12TH EDITION: Steel Scrap – a Raw Material for Steelmaking. Available at: https://www.bir.org/publications/facts-figures/download/821/175/36?method=view
[v] Regan Industrial.com. 2021. How to Repair Damaged or Corroded Steel. Available at: https://reganindustrial.com/blog/repair-damaged-corroded-steel/
[vi] SCI. 2019. Structural steel reuse assessment, testing and design principles. Available at: https://steel-sci.com/assets/downloads/steel-reuse-event-8th-october-2019/SCI_P427.pdf
[vii] Tingley, Danielle Densley and Julian Allwood. 2014. Reuse of structural steel: the opportunities and challenges. Conference paper: European Steel Environment & Energy Congress, September 2014. Available at: https://www.researchgate.net/publication/279441808_Reuse_of_structural_steel_the_opportunities_and_challenges
[viii] Eurofer. 2013. A steel roadmap for a low-carbon Europe 2050. Available at: https://www.eurofer.eu/assets/publications/archive/archive-of-older-eurofer-documents/2013-Roadmap.pdf
[ix] EURIC. 2020. Metal Recycling Factsheet. Available at: https://circulareconomy.europa.eu/platform/en/knowledge/metal-recycling-factsheet-euric
[x] IIMA. 2017. Factsheet: Use of Basic Pig Iron in the Electric Arc Furnace (EAF) for Steelmaking. Available at: https://www.metallics.org/assets/files/Public-Area/Fact-Sheets/_5_Basic_Pig_Iron_in_EAF_Fact_Sheet_rev3.pdf
[xi] Katrin E. Daehn, André Cabrera Serrenho, and Julian M. Allwood. 2017. Environmental Science & Technology 51 (11) : 6599-6606. DOI: 10.1021/acs.est.7b00997
[xii] Reck, K. Barbara and T. E. Graedel. 2012. Challenges in Metal Recycling. Science 337 (6095): 690-695. Available at: https://doi.org/10.1126/science.1217501
[xiii] Reuter et al., 2005; Reuter and van Schaik, 2008, 2012a&b; van Schaik and Reuter, 2012
[xiv] Jin, Hyunsoo and Brajendra Mishra. 2020. Minimization of Copper Contamination in Steel Scrap. Energy Technology 2020: Recycling, Carbon Dioxide Management, and Other Technologies: 357-364. Available at: https://link.springer.com/chapter/10.1007/978-3-030-36830-2_34
[xv] Material Economics. 2020. Preserving value in EU industrial materials. Available at: https://www.climate-kic.org/wp-content/uploads/2020/11/MATERIAL-ECONOMICS-PRESERVING-VALUE-IN-EU-INDUSTRIAL-MATERIALS-2020-compressed.pdf
[xvi] Bell, S., R. Davis Boyd, Javaid Amjad and E. Essadiqi. 2006. Final Report on Effect of Impurities in Steel. Available at: https://www.researchgate.net/publication/306293969_Final_Report_on_Effect_of_Impurities_in_Steel
[xvii] EFR. 2007. EU-27 Steel Scrap Specification. Available at: https://www.euric-aisbl.eu/facts-figures/standards-specifications/download/172/146/32
[xviii] Pauliuk, Stefan Yasushi Kondo, Shinichiro Nakamura and Kenichi Nakajima. 2016. Regional distribution and losses of end-of-life steel throughout multiple product life cycles—Insights from the global multiregional MaTrace model. Resources, Conservation and Recycling 116 (2017) 84–93. Available at: https://pubmed.ncbi.nlm.nih.gov/28216806/
[xix]Weforum. 2015. Metal Recycling: Opportunities, Limits, Infrastructure. Available at: https://www.wrforum.org/wp-content/uploads/2015/03/Metal-Recycling-Opportunities-Limits-Infrastructure-2013Metal_recycling.pdf