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Infrared tech enables recycling of black plastic
- superpermutat0r 8y agoEnergy spent recycling covered by resell value of said plastic?
- TylerE 8y agoThe 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.
- mirimir 8y agoTrue. 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
- noobiemcfoob 8y agoAnd generate worse chemical waste than the plastic was to begin with
- mirimir 8y agoWhy any worse than waste from refining petroleum?
- pjc50 8y agoJust because we can go egg -> omelette does not imply omelette -> egg (Likely it can be done, but the energy involved will be a problem. Most polymerisation is exothermic, so reversing it requires energy input e.g. https://www.ewi.ca/reverse-polymerization.html https://www.ewi.ca/reverse-polymerization.html ) Some plastics can be recycled by simple melting - thermoplastics like ABS. Unfortunately they're often mixed with additives like flame retardants that cause problems.
- mirimir 8y agoUmmm, "omelette -> egg" is a lot harder "plastic -> plastic monomers". And really, if you want to convert omelettes to eggs, you just feed them to chickens. And eventually, you feed unmarketable chickens to pigs.
- Sileni 8y agoChemical 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.
- RandallBrown 8y agoSo it's "just" an energy problem? In a hypothetical future with 100% cheap renewable energy, we could recycle plastic over and over?
- nayuki 8y agoIf we have cheap/free energy, we could just synthesize hydrocarbons instead of digging them out of the ground. As an imperfect analogy, we used to mine fertilizers. Now we use energy to create ammonia directly from nitrogen in the air.
- mirimir 8y agoNo, we make ammonia from nitrogen and methane.
- s0rce 8y agoAssuming 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.
- userbinator 8y agoI suspect this is the reason why something as seemingly trivial as colour is presenting such a huge obstacle to recycling --- the margins are already so low that no one really cares enough to solve the problem. (There is probably a lot of bureaucracy around the whole thing too, which is another impediment.) I believe that identifying what a substance is, is already nearly a solved problem (X-ray fluorescence spectrometers, etc.); it just costs too much to use it.
- prolepunk 8y agoBlack 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-toronto/ https://www.blogto.com/eat_drink/2018/03/black-plastic-toron...
- userbinator 8y agoFrom 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?
- mikepurvis 8y agoSorting 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.
- rcxdude 8y agoDespite the seperate bins you cannot trust the sorting by the public absolutely, further sorting is always required at the recycling center anyway.
- otakucode 8y agoWow, I had never heard of this problem before. At least according to the article you linked, the problem isn't so much the black plastic itself but that optical scanners used in recycling facilities can't read recycling symbols and identify it. Given the amount of black plastic used (I see it all around me right now) I would think solving this problem would do a load of good.
- metildaa 8y agoWe 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.
- 52-6F-62 8y agoThis 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)
- Steve44 8y ago> 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.
- rrggrr 8y agoIf anyone has an automated solution for sorting this kind of thing, I need it. Feel free to email me... insight@hiredinsight.co