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Comment by Maursault | Hacker News Reader

> The dome-bottom uses less material than if the bottom were flat.

How does a dome-bottom, which has considerably more surface area than a flat-bottom. result in less material used?

> A typical aluminum can today contains about 70% recyclable material.

Only 70%!? So out of a half trillion aluminum cans per year, effectively 150B are not recyclable. What is the non-recyclable material, and what happens to it?

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A flat bottom would require a thicker layer of aluminium to provide the same structural properties.

Of course. Thank you.

The other commenter pointing out that not all cans are recycled is part of it, but the other part is that many metals can't be reused as-is and maintain alloy correctly. For instance, if you want to cast aluminum, you don't want melted down cans because those are intended to be stamped and are made from an alloy optimized for that. You would be better off to use some melted down cast aluminum so that it has the right additives for casting, but there are still subtleties in the broader category relating to casting pressure/temperature/etc. So, you might not want 100% recycled material, but rather 70% recycled and purified and then 30% of the right things to get the alloy you want with the properties you want. So, it's probably <100% and >70% of cans getting recycled combined with you want to only use so much recycled material for this application and the rest gets recycled somewhere else.

Cans can only be recycled if they end up in a recycling centre. Cans sent to landfill are functionally non-recyclable, at least for the foreseeable future.

I saw somebody dissolved a soda can in acid, it remained in a plastic bag (which is probably plastic lining inside). But %70 rate seem so low, how does glass fare?

In the Netherlands 80% of all glass is recycled [1] (it is 100% recyclable as long as you don't care about the colour). In the UK the percentage is a bit lower, 67 % for green glass, 48 % for brown glass and 43 % for white glass [2].

[1] https://recyclingnederland.nl/soort/glasrecycling/

[1] https://www.gov.uk/government/statistics/uk-waste-data/uk-st...

Glass has really low rates in the US, 31%. https://tablascreek.typepad.com/tablas/2022/07/why-is-glass-...

In Germany the glass recycling rate is above 80% depending on the year. However this also depends on the source of the glass. According to the German federal Environment Agency only 7% of glass built into cars was recycled, while on the other hand 84,1% of glass sourced from packaging was recycled.

link to the information from the German federal Environment Agency (in German): https://www.umweltbundesamt.de/daten/ressourcen-abfall/verwe...

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