Infrared tech enables recycling of black plastic
yle.fi
yle.fi
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?
But another perspective is that you're recycling petroleum. That is, we make plastic polymers:
petroleum -> chemicals -> plastic polymers
old plastic polymers -> chemicals -> new plastic polymers egg -> omelette
omelette -> egg
Some plastics can be recycled by simple melting - thermoplastics like ABS. Unfortunately they're often mixed with additives like flame retardants that cause problems.
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.
In a hypothetical future with 100% cheap renewable energy, we could recycle plastic over and over?
As an imperfect analogy, we used to mine fertilizers. Now we use energy to create ammonia directly from nitrogen in the air.
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.
Sure, you could theoretically break down most plastics to CO2 and the like. They're a lower energy state than most plastics. The question is why expend the energy to get something we have a huge surplus of. You're not going to be able to get volatiles such as methane or ethylene out of that process efficiently, because it's a higher energy state than the plastics. Tar sands and the like are a mixture of volatiles and heavier compounds; they're not a homogeneous compound the way most plastics are. The compounds going into a thermal cracking system, such as decane, are actually higher in total energy content than the products, such as heptane. They're just more difficult to work with, and as such less valuable economically.
Really, if you're not satisfied with the previous explanation you're going to have to look into an entry level organic chemistry textbook to understand it.
Tsuji et al. (2003) Thermal cracking of oils from waste plastics https://sci-hub.tw/10.1007/s10163-003-0090-x
Walendziewski (2005) Continuous flow cracking of waste https://sci-hub.tw/10.1016/j.fuproc.2004.12.004
Das and Pandey (2007) Pyrolysis and catalytic cracking of municipal plastic waste for recovery of gasoline range hydrocarbons https://core.ac.uk/download/pdf/53188820.pdf
What then? Just landfill it? Recycling mixed plastics is nontrivial. And old-school incineration is a nightmare of toxics emissions.
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.
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.
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)
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.
People are bad enough at contaminating the recycling bins as is, unfortunately (including myself if I'm careless).
Are there really only two types? Where does cellulose fall with regard to those? I've definitely seen cellulose food containers. None of them were ever meant for heating food—only for sealing/containing it for extended shelf-life. This includes bagging, not just hard containers.
It’s also not as functional as OPP films, that is what most of the thin clear sealed plastic packs are made from and also the windows in some packaging. This is being addressed though with products such as Natureflex film which has a cellulose core and moisture barrier coatings on both sides. These barrier coatings themselves are a form of PVC which although not compostable is in an amount which allows the film to pass current certification for composting. This does have a limitation though as it affects the bags ability to be perforated, which many of the OPP bags are.
Natureflex is also, currently, a lot more expensive than OPP so where so much is price driven there isn’t the willingness to do this.
There is a lot of product development going on in packaging and as with most industries quite a few seemingly great ideas are not practical on a large scale.
Seems like an interesting problem space. Way out of my field, but interesting regardless.
I hope there are breakthroughs, including in cost. From a naive standpoint it just seems to make so much more sense to use compostable (esp. easily compostable) organic-based materials to contain...organics.
In commercial composting, where it is sold on to farmers etc., I’m fairly sure there will be a specification as it’ll need to run through their spraying systems and a plastic fork or piece of bag/film could inhibit that.
There is also the issue of partially degraded micro-plastics which are then spread across the field and potentially getting into the food chain.
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.
I would love to see bans on plastic straws and utensils though, as the research on the consequences of those bans and substitution of biodegradable options is much more positive.