[nmehner]

At least in the EU/UK it is required by law to recycle 95% of a car: https://www.autoexpress.co.uk/car-news/95207/car-recycling-h...

A problem with plastics is that it is hard to create high quality plastics from recycled materials. And there is only a limited demand for park benches made from low quality recycled plastics.

This is different with metals where you can "just" melt everything and separate the metals. This is probably less expensive than mining the materials in the first place where the ore contains a much lower share of the metals. Also a car contains a few hundred kilograms of recyclable materials and there is a very limited number of different models. So there is an economic incentive.

[torginus]

Can't we just burn plastics? Most of them are hydrocarbons similar to gasoline. Granted, it's not 100% clean, but the amount of CO2 created by burning all the plastics in the car can't be much worse than a couple tanks worth of gas.

[gst]

What would be the advantage of doing that? We're currently researching CO2 sequestration to remove CO2 from the atmosphere and store it somewhere outside of the atmosphere. So what would we gain by burning plastics? Even if they are not recycled - having those plastics in a landfill is a lot better than burning them and putting CO2 into the atmosphere.

[antupis]

Carbon capture + burning is probably best especially cold places which needs district heating. Eg Norway has now pilot ongoing https://bellona.org/news/ccs/2022-03-oslo-leading-by-example...

[seoaeu]

What? Renewable energy from wind or solar is vastly easier than burning fossil fuel and then trying to get the resulting CO2 back out of the air

[ThunderSizzle]

Vegetation tends to do pretty well at handling CO2.

Also, destroying the landscape to "save the climate" still ends with destroying the environment. Wind and solar aren't energy dense enough to justify the damage they cause.

[seoaeu]

Literally none of what you said is true

[msh]

Solar won't work in Norway in the winter. Wind is too intermittent. So you need an alternative. I don't know if burning stuff and capturing CO2 is a good alternative.

[seoaeu]

The problem with carbon capture is that (a) it takes a lot of energy and (b) is only marginally ahead of fusion on being ready for widespread deployment. So compared to that basically anything is a better alternative.

In the case of Norway, apparently they produce ~90% of their electricity from hydro. Good strategy if there’s lots of spots in your country for hydro electric dams, pretty difficult to replicate if not.

[Delphiza]

We do, and a lot more extensively than people realise. It is called energy recovery. Look for 'Enery Recovery Facility' or something similar. Also known as Waste-to-energy in the US. They are 'good' in a sense that they divert from landfill and try and capture the carbon that they burn. Most people aren't aware of it because the sector doesn't publicise 'burning rubbish' as it sounds worse than 'burning oil'.

[cstejerean]

Or just package it in something that won’t allow the plastic to leech and then bury it for the carbon capture.

[dagurp]

I believe that Sweden does this to generate electricity

[gst]

> This is different with metals where you can "just" melt everything and separate the metals.

How would you separate the metals after melting them? My understanding is that you can extract some high valuable metals via different processes, but otherwise it's technologically and economically not feasible to separate molten metals.

[nmehner]

Well, yes, you are right.

These are actually two steps: Melt everything into the "Black Mass" and use Hydrometallurgy to extract the metals afterwards. I think https://www.youtube.com/watch?v=XylDkcrJgTw gives a good overview (although the voice is somewhat hard to listen to).

[missedthecue]

Different metals have different melting points, don't they?

[Groxx]

To maybe make the other answers a bit more explicit / layman friendly:

Yes, and if you have a bunch of small pieces of different metals all mixed together, you can very carefully melt one, extract it, then the next, etc by gradually raising the temperature.

But if you take an alloy, e.g. bronze, you're combining ~2 metals of different melting points (copper ~1100C, and tin ~230C) to get essentially a new metal with a usually-middling melting point (bronze ~920-970C). Raising bronze to ~300C will not melt the tin out for you to collect. It's not just a surface area issue either, chopping it up into many tiny pieces / a powder won't melt more out and give you something to collect. None will. It'll all melt at bronze's temperature, and until then it all remains solid.

Similarly, if you melt bronze and then cool it down a bit, the copper won't solidify on its own. The whole solution will solidify around 950C. It's kinda like how salty water solidifies at a lower temperature - it's not that the water is freezing at -1C but the salt is not, that'd be a slush (and wouldn't make much sense anyway, salt is solid at room temperature). The solution behaves as a new "whole".

If you want to separate two alloyed metals, you generally have to chemically bind some to something else so it comes out of solution in a way you can capture. Then you can skim it off / extract it from the bottom / etc. One less-visually-obvious strategy is to just keep the alloy hot and exposed to the air, so some of it oxidizes and comes out as slag - that's chemical separation using oxygen. It works pretty well for gold, because unlike many metals gold does not oxidize.

You can also sometimes let the metals separate themselves by density by just letting it sit while melted..... but you'll be fighting against any internal currents set up by temperature differences, so it's difficult, imprecise, and slow to do in practice. But for some combinations and equipment it's feasible.

[gst]

Yes, but if a metal with a lower melting point is in fluid state inside another solid metal that's not better than having both in a fluid (or solid) state.

Here's a related Quora discussion: https://www.quora.com/If-you-smelted-a-varied-mix-of-scrap-m...

[sdenton4]

Seems like you can choose during manufacturing to make things easier to disassemble to enable easier recycling... So the answer to low-melting metals inside high-melting metals is just "Don't do that" because otherwise you'll miss the 95% recyclable policy.