Uppgradering av metallavfall med ‘ShAPE’ kan förändra våra återvinningsvanor

Bättre återvinning

As industrial civilization progresses in time and scale, it becomes clear that we need to optimize our resource utilization. One such activity is metal recycling, with metal-based material, in theory, recyclable endlessly.

I praktiken är det inte så enkelt, eftersom de flesta avfallsströmmar med metallmaterial innehåller en komplex blandning av olika metaller. Ibland beror det på att avfallet är en legering, och ibland skulle det vara för komplext och/eller kostsamt att bara blanda de olika metallerna i den återvunna produkten och sortera dem.

Detta skapar ett problem; att bara återanvända denna metallblandning skulle leda till undermåliga produkter som lättare böjs eller går sönder jämfört med metall tillverkad av färsk malm, vilket kan vara farligt för slutanvändarna.

Till exempel måste aluminiumskrot blandas med 40 % nybrytad och raffinerad aluminium för att kunna återvinnas. Detta hjälper, men det är uppenbarligen inte “verklig” återvinning.

This is why researchers at the Pacific Northwest National Laboratory (PNNL) have developed a new method, called ShAPE  (Shear Assisted Processing and Extrusion). They published how it works and why it can allow for a 100% aluminum recycling rate in the journal Nature Communications, under the title “Upcycled high-strength aluminum alloys from scrap through solid-phase alloying¹“.

Aluminiumåtervinningsproblem

When it comes to aluminum, most of the costs, both money and energy, as well as the assorted CO2 emissions, come from having to completely melt back aluminum, a metal with a high melting point.

This has to be done because recycled aluminum contains small impurities, like clumps of iron. These need to be diluted with fresh aluminum to create a satisfying product.

ShAPE

Instead of spending a lot of energy and additional fresh ore to just create a standard aluminum product, the PNNL researchers found a way to create a better aluminum alloy without all the intermediary steps.

This process directly skips the sorting, melting, and casting steps. Instead, it feeds the aluminum scraps directly into a process called “solid-phase extrusion”, developed in 1993 by the Welding Institute in the United Kingdom.

Solid-phase extrusion uses friction instead of heat to melt the metal, leading to a very homogeneous mix despite using a lot less energy. You can see it in action in the short video below:

The machine has a rotating head that spins 500 times a minute with 2,200 foot-pounds of torque. The other end of the machine contains a hydraulic press capable of exerting 200,000 pounds of force against the rotating head.

Källa: Nature Communications

The aluminum scraps are mixed with copper (Cu) powder, zinc (Zn) powder, and ZK60 magnesium (Mg) ribbons. When uniformly mixed together, they form a high-strength aluminum alloy product in a matter of minutes. In comparison, the traditional aluminum recycling process takes days.

The whole method also consumes 50% less energy.

Källa: PNNL

Överlägsen struktur & prestanda

When analyzed under a microscope, the new method demonstrates a radically different metallic structure. The upcycled material displays much smaller grains (7.7 µm), compared to the traditionally recycled aluminum (43.1 µm).

Källa: Nature Communications

Detta visar att under ShAPE bildas atomskaliga strukturer kallade Guinier-Preston-zoner inom legeringen. Dessa strukturer är välkända för att förbättra styrkan i metalllegeringar.

Det leder direkt till överlägsen prestanda för det uppgraderade metallen, med ett motstånd mot mekanisk belastning 200 % högre än den normalt återvunna legeringen.

Källa: Nature Communications

Another improvement brought by this method is that the production of aluminum profile, tubes, and other metal parts happens in solid-state, potentially helping to develop a new type of alloy that would not work with the traditional melting stages.

Fastfasallergiering är teoretiskt tillämplig på vilken metallkombination du kan föreställa dig, och det faktum att tillverkningen sker helt i fast tillstånd innebär att du kan börja överväga helt nya legeringar som vi tidigare inte har kunnat tillverka.

Cindy Powell – Chief science and technology officer for energy and environment at PNNL

Gå bortom återvunnet aluminium

This technique could be deployed for other metals that are hard to sort or recycle.

It could also be used to produce alloys that have superior performance, such as stronger, safer car structures, or to use less material for the same result.

The same method could also probably be expanded to other solid-phase manufacturing processes. , like cold spray or friction stir welding & processing.

“Vår förmåga att uppgradera skräp är spännande, men det som entusiasmerar mig mest med denna forskning är att fastfasallergiering inte bara är begränsad till aluminiumlegeringar och skräpmaterial.

Cindy Powell – Chief science and technology officer for energy and environment at PNNL

Metall 3D-utskrift

Lastly, this method could be used to create a high-quality feed for metal 3D printers.

Because the method adds a certain amount of extra metals in a precise way, it can be used to create tailored alloys for specific needs in additive manufacturing.

The improved 3D structure is also likely to help make the final 3D printed product extra-strong.

“Det är svårt att få fram matningstrådar med anpassade sammansättningar för trådbaserad additiv tillverkning. Fastfasallergiering är ett fantastiskt sätt att producera skräddarsydda legeringar med exakta sammansättningar såsom 2 procent koppar eller 5 procent koppar.”

Xiao Li – PNNL materials scientist

Aluminiumåtervinningsföretag

Radius Recycling

When new methods for improved recycling are being developed, established players in the industry stand to benefit by taking market share from primary producers.

As we recycle more and more material, as well as we turn toward electrification of heating and transport, the amount of work for recycling companies is poised to grow slowly but steadily. The metal recycling market is expected to grow from $915B in 2024 to $1.29T by 2033, or a 3.9% CAGR.

Radius Recycling was founded in 1906 and currently hires 3,500+ employees. It currently has 100+ sites for metal and automobile recycling all over Canada and the USA, as well as one steel manufacturing site, making it one of the region’s largest metal recyclers.

Källa: Radius Recycling

The company processes both:

• Järnmetaller, som innehåller järn, t.ex. kablar, tunnor, metalltak, cyklar, bilar, hushållsapparater osv.
• Icke-järnmetaller: aluminium, koppar, rostfritt stål, zink, bly-syra batterier, tråd, spolar, elektriska motorer, kylare osv.

In the nonferrous segment, the largest metals are copper and aluminum.

Källa: Radius Recycling

The company is balancing its capital allocation between shareholders (with a dividend paid every quarter since going public in 1993,  – at a yield of 4.5% at the time of writing of this article), controlling debt costs, and reinvestment in growth (including 2 new recovery centers on the US West Coast).

Overall, the company is a good pick for investors looking for exposure to the recycling industry and overall circular economy, a stable dividend income, and activity focused on the North American market.

Studierreferens:

^{1. Wang, T., Li, X., Li, Z., et al. (2024). Upcycled high-strength aluminum alloys from scrap through solid-phase alloying. Nature Communications, 15, 10664. https://doi.org/10.1038/s41467-024-53062-2}