Not as much as you think. Many of the recyclable materials you mentioned are “contaminated” with the contents they were used to deliver because folks don’t wash them well enough. It’s not their fault; we’re told to “rinse” the materials, but they really have to be fully washed, a tough task for many of those cans with crevices and ridges that are often missed. Other contaminants include throwing in what you think is the correct metal or plastic, but it’s not, and that ruins a whole batch.
Comment from a German specialist in a thread about this from 2017:
Die nicht recykelbaren Reste wie Lebensmittelreste, Farbauftrag oder irgendwelche Etiketten verbrennen in der Schmelze und treiben oben auf dem flüssigen Metall als Schlacke, die einfach abgeschöpft und entsorgt werden kann.
Translation:
The non-recyclable residues, such as food scraps, paint coatings or labels burn off in the melt and float to the top of the molten metal as slags, which can simply be skimmed off and disposed of.
Raw materials come from the ground. By your standards of “contamination” aren’t raw materials much more contaminated?
A lot of work goes into refining glass, aluminum, steel, copper etc. A lot of impurities have to be removed to make those materials for the first time.
Raw materials is not what we’re talking about here. Local recycling plants are not processing raw materials - that’s a completely different process. They are very limited systems designed to process consumer materials.
We’re talking about whether recycling is feasible.
Whether or not it is feasible is decided by how hard it is to do compared to just making new materials.
Your comment seemed to be saying the contaminates in recycling make them harder to recycle back to their raw materials (compared to making new raw materials).
Metallurgy isn’t my field, but here’s an educated guess…
There are different kinds of contaminants. In raw ore you largely have silicate rock and metals. In recycled material you have relatively pure metal (alloys), and a large variety of volatiles.
Now with ore you can grind it all into sand, sift it, and smelt all the heavy grains. The rock should mostly just separate from the metal, these are just phase changes. But with recycling, those volatiles are going to burn and some are going to react with the metals, changing the chemical makeup. And with ore, you basically know what minerals you’re working with. With recycled materials, it’s anyone’s guess. Does this can contain some food residue? Or an oil? Perhaps chemical cleaning agents? Is another plastic container stuffed inside?
There’s a lot of variables with recycled materials, I imagine it’s hard to predict how some of those variables react.
Not as much as you think. Many of the recyclable materials you mentioned are “contaminated” with the contents they were used to deliver because folks don’t wash them well enough. It’s not their fault; we’re told to “rinse” the materials, but they really have to be fully washed, a tough task for many of those cans with crevices and ridges that are often missed. Other contaminants include throwing in what you think is the correct metal or plastic, but it’s not, and that ruins a whole batch.
As usual, John Oliver says it best.
Comment from a German specialist in a thread about this from 2017:
Translation:
I was a process engineer in an aluminum plant. While I didn’t directly work in remelt, this is correct as I understand it.
20:1 is the net energy usage for new aluminum smelting:recycling.
Recycle your metals please.
https://m.youtube.com/shorts/f5-Ljn7GX_8
This short explains the German mindset about recycling. The only difference is that in Germany, the letter would be laminated.
Yeah, contaminants aren’t a big deal with metal recycling.
I’m not saying we shouldn’t recycle, we of course should. But most local recycling plants don’t have that capability.
And the biggest problem are plastics - glass and metal materials are much more forgiving.
Raw materials come from the ground. By your standards of “contamination” aren’t raw materials much more contaminated?
A lot of work goes into refining glass, aluminum, steel, copper etc. A lot of impurities have to be removed to make those materials for the first time.
Raw materials is not what we’re talking about here. Local recycling plants are not processing raw materials - that’s a completely different process. They are very limited systems designed to process consumer materials.
Why not make better recycling plants?
Couldn’t agree more
We’re talking about whether recycling is feasible.
Whether or not it is feasible is decided by how hard it is to do compared to just making new materials.
Your comment seemed to be saying the contaminates in recycling make them harder to recycle back to their raw materials (compared to making new raw materials).
Metallurgy isn’t my field, but here’s an educated guess…
There are different kinds of contaminants. In raw ore you largely have silicate rock and metals. In recycled material you have relatively pure metal (alloys), and a large variety of volatiles.
Now with ore you can grind it all into sand, sift it, and smelt all the heavy grains. The rock should mostly just separate from the metal, these are just phase changes. But with recycling, those volatiles are going to burn and some are going to react with the metals, changing the chemical makeup. And with ore, you basically know what minerals you’re working with. With recycled materials, it’s anyone’s guess. Does this can contain some food residue? Or an oil? Perhaps chemical cleaning agents? Is another plastic container stuffed inside?
There’s a lot of variables with recycled materials, I imagine it’s hard to predict how some of those variables react.
For metals, it’s pretty trivial to remove slag (contaminants) from the metal. Basically everything floats to the top and you can just scrape it off.