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Metal and plastic are super easy to separate by density or by electrical conductivity. Batteries are considered hazardous waste and have to be disposed of separ

Metal and plastic are super easy to separate by density or by electrical conductivity. Batteries are considered hazardous waste and have to be disposed of separately, similarly for old electronics or CFL bulbs that contain mercury. But commingled recycling was one of the most predictably stupid moves in the area of environmentalism I've seen in a long time (well, prior to 2016 anyway), when I heard my city was moving to commingled recycling I knew they were no longer actually recycling it, I guarantee almost all of it ends up in the landfill because of contamination. It's so frustrating. At least corn ethanol wasn't obviously quite so stupid upfront, it was always theoretically possible that it would make sense even if it was kind of obvious it wouldn't actually work.

SahAssar 6y ago
> Metal and plastic are super easy to separate by density or by electrical conductivity Yeah, what I meant by better segmentation is not to separate them from each other (we do that) but rather by type. Some plastics are easier to recycle than others and I don't know if metals can be easily and automatically sorted from each other.
- MayeulC 6y ago
  Well, some are magnetic, some are not, that's just one way to differentiate them. Here are a couple videos I know (in French) from consignesdetri.fr: https://youtu.be/KgW1TP909NU?t=36 https://youtu.be/KgW1TP909NU?t=36 (you can see the magnetic belt at that timestamp) https://www.youtube.com/watch?v=vMJ-pDG_afk https://www.youtube.com/watch?v=vMJ-pDG_afk For an aluminium can. They mention doing the same with eddy currents [1] [2] I also recall seeing a big, spiky magnetic roller in some video instead of a magnetic belt, so implementation details can vary, but this seems to be pretty standard stuff. Less standard is the plastic-sorting equipment, though that can be achieved with hyperspectral cameras and the like (read: expensive). In some places, there are separate bins for colored and transparent glass. Some facilities use detectors instead. [1] https://en.wikipedia.org/wiki/Eddy_current_separator https://en.wikipedia.org/wiki/Eddy_current_separator [2] https://en.wikipedia.org/wiki/Eddy_current#Repulsive_effects_and_levitation https://en.wikipedia.org/wiki/Eddy_current#Repulsive_effects...
- 0_____0 6y ago
  Metals can be sorted fairly efficiently. Most types of steel can be pulled out with magnets. Nonmagnetic metals can be sorted from plastic by having a conveyor belt chuck the incoming stream over an gap with a magnetic field applied to it. The magnetic field induces a current in the flying metal, causing the metal itself to become magnetic. This causes the metal to slow down (eddy current braking), and now you have physically separate streams of plastic etc. (fast) and metal (slow).
- neltnerb 6y ago
  Plastic separation is tricky, they tend to have similar physical properties so you end up relying on small density differences or optical properties or computer vision which is obviously not so great. I think most places it's still more cost effective to do it by hand. Metals are easy to separate from one another, they tend to have substantially different densities and electrical properties. Aluminum for instance is not magnetic while steel cans are, but aluminum is conductive so if it passes through a magnetic field it will still get slowed down. Those are the two big ones in any case. Then you could get to things like nickel (magnetic but intermediate conductivity) or tin (light but non magnetic) or maybe zinc/magnesium, but basically the densities are more different and the properties are more different so it's easier to tell them apart. And for some things that it can't figure out it makes sense to just landfill it. Plastics though, absolutely vastly harder. You can use density but it only varies by a few percent. You can use diffraction gratings and cameras to see crystals and maybe sort a bit by that. But really it's just very hard, especially since the same polymer has different molecular weights and crystallinity. Your milk jug is milky while the same molecule processed differently is clear. But even that's a mess -- you can't generally "depolymerize" these things very easily, you are really melting them back together and reusing the melt. When you start from monomers you can control the molecular weight (chain length) which controls things like crystallinity and stiffness, so the quality is higher. If you melt a variety of different molecular weights back together even if they're the same exact molecule the physical properties will just by worse. It's just the nature of the beast, and it sucks. Even if you recycle by perfectly melting all the PET with perfect sorting and no food residue you'll be guaranteed to increase the variability in the physical properties of the output. It's just chemistry, unless you can convert it back to monomers it'll never be as good even in the best case. For metals at least you can count on a fairly full recovery if you invest in it, it's not like polymers where it's just not possible. Even with alloys like steel you can at least in principle go back to the raw materials if you wanted, even if they are quite tricky.
  - SahAssar 6y ago
    So what you're saying is that separating glass, cardboard, paper, compost, metal (which we can separate from one another if it is just metal by the methods you described) is valuable, but the all plastic can go in the "general" type, right? Glass, cardboard, paper and compost are either recyclable or reusable, metal is recyclable when sorted correctly, and plastics are pretty much a no-go as the parent article suggests, right?
LargoLasskhyfv 6y ago
Batteries are hazardous! You can take an empty AA-cell and drive a nail with a hammer through the middle from the side. It makes buzzing and popping sounds, and there are blue-white arcs/tendrils all over it and the nail for maybe half a minute. Like crazy CGI in a movie! And it STINKS! That is for non-rechargables. Haven't tried that with rechargables.
- neltnerb 6y ago
  They are worse, lithium batteries tend to explode or catch fire. Cool description, I've never noticed these tendrils you describe.
  - LargoLasskhyfv 6y ago
    I couldn't believe it either! Don't know if it were alakaline or something else anymore. I'm using rechargable Eneloops now, where possible. Honestly I can't remember anymore what has driven me to do that? Maybe frustration because empty so fast?
    - neltnerb 6y ago
      Awesome. They seem like a good choice, only a little lower capacity than alkaline and seem to hold capacity well. Much better than those old NiCd batteries. The main downside is that the NiMH chemistry is 1.2V instead of 1.5V like alkaline. Same kind of issue as with the older NiCd batteries where they just didn't seem to put out as much juice. They just have a lower voltage. Personally I'm not really sure how to do that best. Ideally you'd design electronics to run on a lower voltage to start with and always use rechargeable batteries but if they were going to do that you'd figure there'd just be a Li-Ion battery in there already. Must be primarily for cases where energy density or weight is the only consideration and waste is a very secondary concern. My roomate used to work at A123 and one of his jobs was literally to drive nails through their lithium batteries to make sure they wouldn't explode. I think it's just a natural human drive to do things like throw batteries into a fire or drive nails through them or put them in a blender. We're a very strange species.

SahAssar 6y ago

> Metal and plastic are super easy to separate by density or by electrical conductivity Yeah, what I meant by better segmentation is not to separate them from each other (we do that) but rather by type. Some plastics are easier to recycle than others and I don't know if metals can be easily and automatically sorted from each other.

MayeulC 6y ago
Well, some are magnetic, some are not, that's just one way to differentiate them. Here are a couple videos I know (in French) from consignesdetri.fr: https://youtu.be/KgW1TP909NU?t=36 https://youtu.be/KgW1TP909NU?t=36 (you can see the magnetic belt at that timestamp) https://www.youtube.com/watch?v=vMJ-pDG_afk https://www.youtube.com/watch?v=vMJ-pDG_afk For an aluminium can. They mention doing the same with eddy currents [1] [2] I also recall seeing a big, spiky magnetic roller in some video instead of a magnetic belt, so implementation details can vary, but this seems to be pretty standard stuff. Less standard is the plastic-sorting equipment, though that can be achieved with hyperspectral cameras and the like (read: expensive). In some places, there are separate bins for colored and transparent glass. Some facilities use detectors instead. [1] https://en.wikipedia.org/wiki/Eddy_current_separator https://en.wikipedia.org/wiki/Eddy_current_separator [2] https://en.wikipedia.org/wiki/Eddy_current#Repulsive_effects_and_levitation https://en.wikipedia.org/wiki/Eddy_current#Repulsive_effects...
0_____0 6y ago
Metals can be sorted fairly efficiently. Most types of steel can be pulled out with magnets. Nonmagnetic metals can be sorted from plastic by having a conveyor belt chuck the incoming stream over an gap with a magnetic field applied to it. The magnetic field induces a current in the flying metal, causing the metal itself to become magnetic. This causes the metal to slow down (eddy current braking), and now you have physically separate streams of plastic etc. (fast) and metal (slow).
neltnerb 6y ago
Plastic separation is tricky, they tend to have similar physical properties so you end up relying on small density differences or optical properties or computer vision which is obviously not so great. I think most places it's still more cost effective to do it by hand. Metals are easy to separate from one another, they tend to have substantially different densities and electrical properties. Aluminum for instance is not magnetic while steel cans are, but aluminum is conductive so if it passes through a magnetic field it will still get slowed down. Those are the two big ones in any case. Then you could get to things like nickel (magnetic but intermediate conductivity) or tin (light but non magnetic) or maybe zinc/magnesium, but basically the densities are more different and the properties are more different so it's easier to tell them apart. And for some things that it can't figure out it makes sense to just landfill it. Plastics though, absolutely vastly harder. You can use density but it only varies by a few percent. You can use diffraction gratings and cameras to see crystals and maybe sort a bit by that. But really it's just very hard, especially since the same polymer has different molecular weights and crystallinity. Your milk jug is milky while the same molecule processed differently is clear. But even that's a mess -- you can't generally "depolymerize" these things very easily, you are really melting them back together and reusing the melt. When you start from monomers you can control the molecular weight (chain length) which controls things like crystallinity and stiffness, so the quality is higher. If you melt a variety of different molecular weights back together even if they're the same exact molecule the physical properties will just by worse. It's just the nature of the beast, and it sucks. Even if you recycle by perfectly melting all the PET with perfect sorting and no food residue you'll be guaranteed to increase the variability in the physical properties of the output. It's just chemistry, unless you can convert it back to monomers it'll never be as good even in the best case. For metals at least you can count on a fairly full recovery if you invest in it, it's not like polymers where it's just not possible. Even with alloys like steel you can at least in principle go back to the raw materials if you wanted, even if they are quite tricky.
- SahAssar 6y ago
  So what you're saying is that separating glass, cardboard, paper, compost, metal (which we can separate from one another if it is just metal by the methods you described) is valuable, but the all plastic can go in the "general" type, right? Glass, cardboard, paper and compost are either recyclable or reusable, metal is recyclable when sorted correctly, and plastics are pretty much a no-go as the parent article suggests, right?

LargoLasskhyfv 6y ago

Batteries are hazardous! You can take an empty AA-cell and drive a nail with a hammer through the middle from the side. It makes buzzing and popping sounds, and there are blue-white arcs/tendrils all over it and the nail for maybe half a minute. Like crazy CGI in a movie! And it STINKS! That is for non-rechargables. Haven't tried that with rechargables.

neltnerb 6y ago
They are worse, lithium batteries tend to explode or catch fire. Cool description, I've never noticed these tendrils you describe.
- LargoLasskhyfv 6y ago
  I couldn't believe it either! Don't know if it were alakaline or something else anymore. I'm using rechargable Eneloops now, where possible. Honestly I can't remember anymore what has driven me to do that? Maybe frustration because empty so fast?
  - neltnerb 6y ago
    Awesome. They seem like a good choice, only a little lower capacity than alkaline and seem to hold capacity well. Much better than those old NiCd batteries. The main downside is that the NiMH chemistry is 1.2V instead of 1.5V like alkaline. Same kind of issue as with the older NiCd batteries where they just didn't seem to put out as much juice. They just have a lower voltage. Personally I'm not really sure how to do that best. Ideally you'd design electronics to run on a lower voltage to start with and always use rechargeable batteries but if they were going to do that you'd figure there'd just be a Li-Ion battery in there already. Must be primarily for cases where energy density or weight is the only consideration and waste is a very secondary concern. My roomate used to work at A123 and one of his jobs was literally to drive nails through their lithium batteries to make sure they wouldn't explode. I think it's just a natural human drive to do things like throw batteries into a fire or drive nails through them or put them in a blender. We're a very strange species.