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Recycling plastic vs degrading plastic
- This topic has 7 replies, 5 voices, and was last updated 4 years ago by
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Hey guys,
Recycling is so great and I love Dave’s attitude and vision here.
Now not all plastic on the planet can be recycled, and here is a new interesting way of degrading it : caterpillar enzym.
That’s a nice specimen but it transforms plastic into … C2H6O2 (ethylene glycol), which is very toxic ! So you could not just throw tons of this enzyme, it would be a real disaster for our planet. Plastic would certainly has to be collected before treating it with this enzyme. So I don’t think it’s that revolutionary so far. I’m still really excited to see if we can overcome this problem.
Several years ago I got to discuss the subject of biodegradable plastics, being plastics that are being marketed as “environmentally friendly” with an academic from the engineering faculty, who seemed to have a professional interest in such matters. IIRC the set of conditions required for degradation of those plastics was (bearing in mind that it apparently was early days for biodegradable plastics as product) quite outside the range of conditions likely to be encountered (eg very hot temparatures sustained in duration). So the view was that though biodegradable plastics are an important idea, they will need to continue to develop to become efficient & more than marketing tool…and as ever the costs need to be competitive (both in terms of production & recycling) with existing plastics that we merely discard in massive quantities.
I heard of researchers looking into the breakdown of styrofoam using superworms (being a particular type of beetle larvae), which similarly sounds promising in expediting the breakdown of discarded styrofoam, but may introduce undesirable compounds into the food-chain (for the worms and for those organisms higher up).
Until we really understand the impacts of introducing those compounds into the food-chain, we’ve got to be cautious, but I think it’s a very big push for that research to be undertaken on the various compounds that are included in the umbrella-term plastic.
Another opportunity may exist in the use of fungi to break-down plastics, as already occurs in dealing with other waste. Again the same risks as using insects may be present. This article suggests that fungi may be functioning as a transport layer for nutrients, perhaps providing opportunity to control the degradation process rather than being stuck in a mindset where it seems (miraculous) alchemy is required to appropriately deal with the less-than-desirable consequences of our dependence on plastic.
Has anyone seen any explanations of the chemistry of the decomposition of (the various kinds of) plastic?
I’ve seen figures thrown around that it takes hundreds, or thousands of years, but I’d like to see explanations for each of the various types of plastic in common use made available for consideration/discussion.
So I went looking for some forum-style explanations about the decomposition of plastics to capture the range of (cough) sentiments, rather than single source explanations.
What is produced from the bio-degradation of plastics.
Why are plastics not bio-degrdable?
Plastic eating fungi may aid World’s Waste problem.
My expectation that is that existing molecular bonds will (somehow be) severed, or new bonds created. What are the properties of the resulting compounds & elements? Are they stable, safe/unsafe, useful….?
It seems that using organisms (microbes) to break-down plastics is referred to as Bioremediation.
This lecture on Environmental Microbiology introduces many of the concepts that seem relevant to understanding the environment and the interaction that exists between components as part of various cycles.
Another lecture provides a more detailed understanding of what occurs in degradation processes and mentions the biodegradation database. It’s a bit more heavy going, but if you try to keep floating at the concept level, the big picture is not completely obscured.
@ikbonzumpferl Maybe I hav a partitial answer for you. I am reading two plastic recycling books in the moment and just now I came across the degrading issue of recycling plastic over and over again.
To understand the process, you have to know that polymeres are long chains of repeating molecular patterns the length of these molecules not being defined (Poly-…).
When heating a substance, you basically increase the particle velocity of the material. There is a rule of thumb saying that an increase of 10°C doubles the speed of chemical reactions. So that explains why it takes ages for plastic to degrade naturally, but only a few times heating it up to do the same.
When degrading, the long polymeres are split, reducing the length of the molecules. Doing this over and over again changes the properties drastically (molecular mass, colour, branching rate, cross-linkage, crystallinity and grade of impurity)
So I hope this somehow helps a little 🙂
That is at least how I think the process of degrading in the nature works. Molecules getting smaller and smaller until they eventually become a part of the soil (after maaany decades 😉
Better start farming worms right now, you will need a crazy amount of worms to actually be able to make a difference. But this actrually looks like a good option to start cleaning up the plastic that is hard to recycle.
How to contain those worms?
Are there plastic types that can be recycled that they don’t like to eat?
Then we could design worm houses for them
Yep, I’ve seen some nylon being produced….nice long chains.
I had been filming a Bronze sculptor recently and looking into matters bronze, which as an alloy seems to (perhaps similarly) suffer from decomposition into it’s elemental forms, which in it’s fast & undesirable form is called “Bronze disease”.
Perhaps also relevant from Bronze sculpting, which sees sheet bronze cut and manipulated into shape (as opposed to being cast), the early processes to enable the bronze after it has been cut into shape is to heat and bash the bronze to introduce imperfection into the bonds, so that the bronze becomes easier to subsequently work with.
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