By Melissa Zirps, Magrathea.
The past decade has seen a significant global shift towards sustainability and decarbonization. To meet this era of decarbonization, the industrial sector, responsible for a quarter of all global emissions, has had to reevaluate processes and resource utilization.1 Within this sector, the aluminum industry is a significant contributor, responsible for 3% of global industrial emissions.2 However, aluminum is essential to a high quality of life, as it is used across a wide swath of industries, from food and beverage packaging to virtually all forms of transportation.
Though aluminum is essential to society, primary production still emits 12-14 kg CO2e/kg Al on average, with even the lowest embodied carbon primary aluminum products emitting just 3-4 kg CO2e/kg Al. The aluminum industry must decarbonize, and secondary aluminum (scrap recycling) offers a compelling solution to the industry.3-4 This is why so many aluminum companies have made commitments to “circularity.” Keeping aluminum scrap as aluminum is the best and simplest way to rapidly decarbonize aluminum.5
However, the allure of using scrap aluminum as an agent of decarbonization has inadvertently diffused into other industries. Now there are a number of proposals to divert aluminum scrap from the recycling stream to be used as a consumable reagent to make other materials. Some see scrap aluminum as stored energy that can unlock a pathway to decarbonize the production of commodities such as hydrogen, silicon, and magnesium. However, pursuing non-circular applications of scrap aluminum poses a challenge to the aluminum industry’s carbon mitigation and circularity goals and will likely result in severe, long term environmental consequences. Furthermore, even the business case for these proposals is unconvincing because scrap aluminum is increasingly coveted by the aluminum industry to achieve decarbonization goals. Disrupting aluminum circularity to produce assets that have other feasible routes to primary production makes no environmental or commercial sense.
Aluminum Scrap is Critical for Aluminum Decarbonization
Deep decarbonization and impact reduction of primary aluminum production is notoriously difficult. Bauxite, the raw material used for primary aluminum production, must be open pit mined from vital ecological sites, such as the Amazon, clearing vast swathes of primary rainforest, disrupting ecosystems, and releasing carbon through deforestation.6 Additionally, the mining process generates large volumes of waste, including toxic bauxite residue, also called red mud, which can contaminate local drinking water sources and harm aquatic life.
Challenges to reduce environmental impact also persist in the smelting process. The industry is still working to address emissions caused by anode consumption in the Hall-Heroult process and waste production from spent pot linings and dross.7 As a result, the industry is struggling to find solutions to the emissions and waste streams inherent to every stage of production, from bauxite to alumina and primary aluminum.
Though there are many unanswered questions around primary aluminum decarbonization, aluminum demand is expected to increase in the coming years, driven by sustainability initiatives further up the supply chain. Increased demand for electric vehicles and solar panels will single-handedly drive aluminum demand up before accounting for typical market growth.8-9
To supply the demand of the growing markets and comply with internal and external pressures to reduce environmental impacts, the aluminum industry has turned to aluminum scrap. Aluminum scrap is incredibly amenable to recycling and reuse, and because it is a secondary product, it is considered to have low embodied carbon emissions according to some carbon accounting methodologies. Regardless, recycling aluminum scrap into secondary aluminum ingots consumes only 5% of the energy needed in primary aluminum production.10 Aluminum is also exceptionally recyclable or “near circular,” with losses of only 2–10% with every remelt. The growing demand for aluminum coupled with the struggles to reduce impact and decarbonize primary production has led to the creation of systems to collect not only pre-consumer scrap (“new” scrap from the machining and fabrication processes), but also post-consumer scrap (“old” scrap at end of life).11
However, scrap aluminum is a finite resource, and in an era of decarbonization, it has become a sought-after material of construction. Conservation of mass constrains the amount of secondary aluminum to the amount of primary aluminum ever produced. Further, aluminum only becomes post-consumer scrap at end of use. In a growing market, the cumulative material reaching end of use will always be less than the current demand for new material.
On top of this, recovery rates of post-consumer aluminum must also be considered, which are only 38% in the U.S.12 Constellium stated in their 2015 life cycle assessment that “the main challenge of aluminum recycling is scrap availability.”13 This is still true today, with secondary aluminum making up only a third of the current market.2
Novelis stated in their 2023 sustainability report, “We explore opportunities to increase the amount of recycled content in our products but are limited by factors like scrap availability.”5 Subsequently, a market with higher demand than supply may drive up prices for aluminum scrap. This is an unpredictable and potentially unstable input to be reliant on to make alternative products such as hydrogen or magnesium, which can both be made using alternative, low carbon methods (like producing magnesium from infinitely abundant seawater).
The Problem with Scrap as a Consumable Reagent
The aluminum industry is dependent on aluminum scrap to meet decarbonization goals, yet the available scrap supply cannot support the entire aluminum market.14 Therefore, diverting scrap from secondary aluminum production to use it as a consumable reagent for alternative material production is counterproductive and inadvertently contributes to environmental degradation. Because scrap aluminum is a finite resource, consuming it in alternative processes takes scrap away from its fundamentally ideal use case as secondary aluminum, resulting in increased demand for primary aluminum to meet growing demands. That in turn means more carbon emissions and more open-pit mining in places like the Amazon rainforest. Disrupting aluminum circularity is illogical from the perspective of sustainability.
Proponents of these processes that take scrap away from circularity argue that they use the so-called “bad” scrap. They claim there is no use case for this type of scrap as secondary aluminum, citing predictions of excess accumulation of this “bad” scrap, which is sometimes referred to as “scrap surplus.” The scrap surplus is a highly uncertain concept that is predicted by some researchers to amass due to the downcycling of aluminum resulting from contamination, primarily from poor sorting of alloys, which will cause it to ultimately exceed demand for “lower quality” applications (Figure 1).15
However, arguing that this scrap is a waste product is misguided. Instead, this impending scrap surplus, coupled with aggressive circularity and decarbonization goals, serves as a catalyst for the aluminum industry to improve sorting and refining technology to expand the recycling of post-consumer scrap for high quality applications. The solution to “bad” scrap is to develop technologies to turn it back into aluminum, not throw it out.16
Beyond the environmental implications of driving up primary aluminum production, there does not appear to be a compelling business case for diverting scrap aluminum to alternative applications. The cost of raw materials is a critical factor in industrial processes, and having a production process rely on a scarce and finite material that is fundamental to the decarbonization of a major industry results in a highly unfavorable cost structure and a large long-term risk for those technologies and projects. No one should want to lock into a cost structure predicated on the use of a large amount of a highly coveted commodity to meet their decarbonization goals.
Looking Forward
Attempts to disrupt aluminum circularity to produce other commodities such as hydrogen, silicon, and magnesium, while well-intentioned, pose risks to the decarbonization of the aluminum industry. Aluminum is an essential building block for civilization and is fundamental to the clean energy transition. Decarbonization of primary production is not on the near horizon, which makes scrap aluminum for secondary production a keystone strategy for rapid decarbonization. Therefore, other commodities industries attempting to decarbonize should look to other production methods for emissions reductions that don’t disrupt circularity and decarbonization in an industry as critical as aluminum.
References
- “CO2 Emissions in 2022,” International Energy Agency, March 2023.
- Simon, Richard and Tiffany Vass, “Aluminium,” International Energy Agency, July 2023.
- Saevarsdottir, Gudrun, et al.“Reducing the Carbon Footprint: Primary Production of Aluminum and Silicon with Changing Energy Systems,” Journal of Sustainable Metallurgy, August 2021.
- “Reduce your carbon footprint with low-carbon aluminium,” Norsk Hydro, September 4, 2019.
- “Scaling Circularity: 2023 Sustainability Report,” Novelis, 2023.
- “Ford F-150 Electric Pickup Built from Metal Damaging the Rainforest,” Bloomberg, Feb 26, 2023.
- Das, Subodh, “The Quest for Low Carbon Aluminum: Developing a Sustainability Index,” Light Metal Age, February 2021.
- “Pathways to Commercial Liftoff: Industrial Decarbonization,” U.S. DOE, September 2023.
- “Critical Materials Assessment,” U.S. DOE, May 2023.
- “Aluminum: The Element of Sustainability,” The Aluminum Association, September 2011.
- Das, Subodh and Martin Hartlieb, “Addressing the Problem of Greenwashing in the Aluminum Industry,” Light Metal Age, August 2022.
- “Mineral Commodity Summaries 2024,” U.S. Geological Survey, 2024.
- “The Life-Cycle of Aluminum,” Constellium, October 13, 2015.
- Aleksić, Jelena and Daniel Boero Vargas, “Aluminium demand will rise 40% by 2030. Here’s how to make it sustainable,” World Economic Forum, November 28, 2023.
- Van den Eynde, Simon, et al., “Forecasting global aluminium flows to demonstrate the need for improved sorting and recycling methods,” Waste Management, Vol. 137, January 1, 2022, pp. 231–240.
- van Heusden, Renée, et al., “The answer to the aluminium industry’s emissions issue? Aluminium’s infinite recyclability,” World Economic Forum, December 9, 2021.
Edited on July 15, 2024: When first published online, this article was incorrectly labeled under “Magnesium,” and we have corrected the label to fall under “Aluminum Remelt & Recycling,” which more accurately reflects the content of the article. Note that articles published in Light Metal Age may express the opinions of the author or company and do not necessarily reflect the views of the publisher.
Melissa Zirps is a metallurgical engineer at Magrathea. Before coming to Magrathea, Zirps was at Stanford University, pursuing a PhD in structural engineering. Her PhD research focused on numerical modeling of corrosion, specifically in reinforced concrete, and her dissertation was entitled “Sustainable Management and Deterioration Modeling of Reinforced Concrete.” She defended her PhD in June 2023.
Editor’s Note: This article first appeared in the June 2024 issue of Light Metal Age. To receive the current issue, please subscribe.