
Infrared tech enables recycling of black plastic - cromulent
https://yle.fi/uutiset/osasto/news/finnish_tech_enables_recycling_of_black_plastic/10716818
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prolepunk
Black plastic is a big deal as most of the food containers are made of black
plastic, and cities have trouble recycling them, even though the plastic
itself is recyclable [https://www.blogto.com/eat_drink/2018/03/black-plastic-
toron...](https://www.blogto.com/eat_drink/2018/03/black-plastic-toronto/)

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userbinator
From that article:

 _black doesn 't reflect enough light for optical scanners to identify
recycling codes, making it difficult to sort these types of containers
properly_

I wonder if this is similar to the "face recognition doesn't work on dark
skin" problem --- there was a lot of planning and design involved in the
systems required to process the plastic, and even testing, but no one thought
to test with _black_ until very very late in the process?

Given that people already have to sort the different types of trash, isn't it
not too unreasonable to ask them to sort the plastic too?

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mikepurvis
Sorting between two or three bins is fine, but there are like seven codes for
recyclable containers— as a purely practical matter, it would not be realistic
to place seven different bins at the curbside.

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superpermutat0r
Energy spent recycling covered by resell value of said plastic?

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TylerE
The biggest problem is you can't _really_ recycle plastic. It would more
accurately be called downcycling, as what you get out is of a much lower grade
than what you put in. Contrast with aluminum where you get...aluminum back
out.

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mirimir
True.

But another perspective is that you're recycling petroleum. That is, we make
plastic polymers:

    
    
       petroleum -> chemicals -> plastic polymers
    

So why can't we use plastic polymers like petroleum?

    
    
       old plastic polymers -> chemicals -> new plastic polymers

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Sileni
Chemical reactions are typically driven by moving from a high potential energy
state to a lower potential energy state. Polymers are incredibly stable
because of their binding mechanisms. It takes a relatively large amount of
energy to break down those bonds, and when you do, your end product is
something far more stable than the original chemicals you started with. Which
means it reacts less readily than the chemicals you started with.

Take for example polyethylene, a product we can recycle relatively well. The
first reaction gives polyethylene chains of length N. Because they're as long
as a polyethylene chain can be, they're as strong as polyethylene can be, and
have the best performance characteristics you can expect. Each time they're
heated up to be remolded or have contaminants removed, and to a lesser extent
just from use and contact with sunlight, some of those chains break. This
creates more N/(2^x) length chains. This causes the plastic to get weaker over
time. The energy cost to recombine those chains would consume more petroleum
than simply creating new plastics, if it could be done at all.

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RandallBrown
So it's "just" an energy problem?

In a hypothetical future with 100% cheap renewable energy, we could recycle
plastic over and over?

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s0rce
Assuming unlimited energy you could just take CO2 from the atmosphere and
react it with hydrogen from water to synthesize all the hydrocarbon precursors
you need to then make plastics. The plastics could be burned and you start
over again.

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mirimir
Sure, we can burn plastics. But that can be problematic, because they often
contain metals (either as filler, or in multiple layers) and are typically
contaminated.

In a closed system, where you're just cracking plastics, it's arguably easier
to deal with contaminants. And I also suspect that you'd use less energy
overall.

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rrggrr
If anyone has an automated solution for sorting this kind of thing, I need it.
Feel free to email me... insight@hiredinsight.co

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metildaa
We need to continue pushing plastic packaging out of everyday life.

Seattle banned plastic bags, take out containers/utensils and other single use
plastics, and suddenly I'm able to get plant based nearly plastic utensils,
containers & straws that do the same thing but can be composted.

This isn't a huge change for consumers, but it does move a large chunk of
waste from the recycle & trashcan into the yard waste bin, which is a huge
step for ensuring that waste is reused.

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52-6F-62
This has always been my question.

Decomposable plastics are not new and they’re perfectly usable for “throwaway”
containers. I’ve always wondered why they’re not more commonly used in these
cases.

(I have a sad laugh at the organic “non-gmo” vegetables sold in hard-to-
recycle plastic containers in grocery stores as well)

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Steve44
> Decomposable plastics are not new and they’re perfectly usable for
> “throwaway” containers. I’ve always wondered why they’re not more commonly
> used in these cases.

There are basically two types of "compostable" [1] plastic. One type uses an
additive which allegedly breaks down the long polymer chains into smaller
pieces which are then degradable. These come under a few titles, but generally
called oxo-degradable. Most scientific consensus is these are nasty and just
result in micro-plastic fragments being left behind.

The second is PLA, derived from corn starch. This can look like regular
plastic but has a lot of limitations, mainly around the usable temperature
range and isn’t suitable for any warm/hot use. There are derivations such as
C-PLA which can be used for cutlery and some other limited uses, it still
doesn’t perform that well with heat though.

Both of these also have challenges for their end-of-life processing. They both
look like regular plastic and are very hard / impossible to sort from regular
plastic which means it’s very hard to avoid contamination both ways. If some
regular plastic gets into the composting stream then the whole batch of
compost is contaminated and will need to destroyed. Likewise, degradable
plastic contamination will destroy a recycling batch.

It’s horrendously complex and involves the whole product lifecycle.

[1] Note I’ve used the term loosely as it’s a lot more complicated than that
as compostable doesn’t mean what the man ins the street generally thinks it
does.

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jdeibele
Thanks for the detailed answer.

I've seen white, clear, and black "plastic" utensils. Most were plastic from
petroleum, some from corn. Seems like it would be nice if C-PLA utensils were
to be dyed green so it could be separated from the rest.

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Steve44
Interesting idea but there is no way you could get worldwide manufacturing to
have a fixed colour scheme for products. Having said that, never say never…..

