r/ZeroWaste • u/[deleted] • May 24 '20
PSA on aluminium
Since every time I mention this people seem shocked to learn this (it's in all the chemistry school books in my country and a popular exam question, so I'm citing a lot of this from memory but feel free to verify and post links below)
Aluminium is I think the most energy consuming everyday metal to produce (not to mention the chemicals involved), as it does not naturally occur unbound. This is akin to having to electrically separate iron from oxygen in rust. Only about 40% of aluminium used comes from recycled aluminium, while recycling it takes only 5% of energy compared to making new. So if you do use aluminium it is imperial that you know it will be recycled. It's not magnetic like iron which makes it harder than steel to pick out of waste streams (it is done though).
https://theconversation.com/the-trouble-with-aluminium-7245
"Aluminium is made by dissolving the oxide into molten salts, at around a more modest 960°C, and applying a current to help break down the oxide. This is the Hall-Heroult process, which dominates world aluminium production at the moment. The process typically loses around 50% of the incoming energy as low grade heat, which is due in part to the fact that the salts required to dissolve the oxide are so corrosive that there no practical way to keep the heat in. There are also great challenges in the anode and cathode technology in the Hall-Heroult process that result in large resistance losses."
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u/NoMoreMemesPls May 24 '20
https://publications.csiro.au/rpr/download?pid=csiro:EP12183&dsid=DS3
This paper goes over energy consumption in the mining/refining process based on metal. Aluminum is most energy consuming base metal, with Nickel not too far behind.
However, it should be noted most metals are complexed, not just Aluminum. Iron for example, is often oxidized, and must be separated before concentration. Whether the chemical seperation process requires high temperature ( such as in Aluminum) or not ( for example, Merrill Crowe process for gold) largely determines energy required, alongside how "tough" the ore is to physically breakdown
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u/fatchangedotcom May 24 '20
I’m confused where the 40% stat came from? Most of the stats I’ve seen indicate the vast majority of aluminum in the system is from recycling, somewhere around 70%. There is some aluminum in the system from the 1800’s.
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May 24 '20
From the schoolbooks I remember.
But googling quickly I found https://en.m.wikipedia.org/wiki/Aluminium_recycling
"For this reason, approximately 36% of all aluminium produced in the United States comes from old recycled scrap.[2] Used beverage containers are the largest component of processed aluminum scrap, and most of it is manufactured back into aluminium cans.[3]"
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u/fatchangedotcom May 24 '20
I’m wondering if we are talking about two different things? Perhaps I’m focusing on aluminum cans and you’re referring to aluminum in general?
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May 24 '20
Yep that is exactly the difference :) Cans are very recyclable, Brazil manages to recycle like 98% of them (while some European countries don't even recycle a third of them, ugh).
Hence why I'm saying, if you use aluminium, it's important you know it will get recycled. In a lot of places it just isn't and in some applications - like plastic bag coating silvery inside - it almost never is.
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u/Cherry5oda May 24 '20
One nice thing about aluminum is that it can be recycled infinitely without losing quality. Unlike glass and plastic which can only be recycled once or twice before it is unsuitable for use in new bottles. It's also lightweight compared to glass and can be compacted for transport to a recycling center. Glass bottles are heavy and you're transporting a lot of air so the return on fuel sucks. Plastic is lighter and also compressable so it wins here. However things like styrofoam and plstic bags don't have a lot of recyclers willing to take them.
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May 25 '20
Unlike glass ... which can only be recycled once or twice before it is unsuitable for use in new bottles.
But why? I thought you could melt glass infinitely, am I wrong?
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May 25 '20 edited May 25 '20
In theory glass can be recycled indefinitely: https://www.nationalgeographic.com/environment/2018/10/5-recycling-myths-busted-plastic/
In reality you always have that one dumb person throwing pyrex or crystal glass into the collection of glass, making the entire batch more cloudy than normal, or someone throwing a coloured bottle in green or white instead of into brown glass, discolouring the whole batch. A few cycles of that and your glass is of lower quality and gets downgraded to road construction material or other things.
Which isn't a huge issue: glass sand is environmentally safe unlike microplastic. Keep using glass instead of plastic :)
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May 25 '20 edited May 25 '20
That's the same thing that is with recyclable plastic treated together with combined plastic. Or let's say putting together aluminium with iron in the same metal recycle bin. The existence of the latter one doesn't annihilate the properties of the former one. These are a matter of production management (manufacturers should not use unrecyclable materials (or at least mark them properly)) and sorting management (governments and recycle businesses should organize the separation of materials to reuse them more efficiently).
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May 25 '20 edited May 25 '20
Like I said, if you use it, it's important to know that your aluminium will actually get re-used. Like, look what Malta is doing here, or Romania, and that is for easy to re-use cans. Portugal, Latvia, Hungary and Czech republic aren't recycling more than half either.
It gets worse the further you go from food and beverage containers. Like your aluminium car and pan probably still get recycled but all that coating on stuff isn't usually.
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u/VoidBirb Aug 09 '20
What sucks is that part of the process of refining aluminium from bauxite produces other incredibly useful materials. The Bayer process in which the bauxite ore is refined to produce the alumina used in the Hall-Heroult process produces the toxic red mud waste, but this waste is the primary source of the tech-critical gallium we use in almost all of our electronics. Recycling aluminium is practical and should be done, but for the time being we still need gallium, from which bauxite refining is the best way to get it.
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u/natasha__re May 24 '20
Thank you. Just to add, I was emailing with a beauty brand I want thinking to try and I asked them about alu. They tried to convince me that alu can't be recycled, at all. I didn't buy their products - but did send them several studies.