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Comment by swiley | Hacker News Reader

PLA can be recycled with near perfect efficiency and is available today.

Also it's extremely biodegradable so throwing it out isn't the end of the world.

No, it's not. Despite what store pages love to tell you at every corner, PLA does not degrade by itself. It requires exposure to 60+ degrees Celsius for at least 6 months. Good luck building recycling plants handling this in an environmentally-friendly and economical way.

Don't throw out PLA, it's barely less problematic than other materials.

Temperature at land fills get rather high. Not sure about 6 months, it depends where.

I've personally seen how PLA degrades in good compost in about three weeks (can go for less if you're more active). True, it is important to go through a stage of 60+℃ for a day or so, to soften up so bacteria get in, otherwise it may indeed take 6 months to get through a solid chunk, but that is quite different from 6+ months of 60+℃.

Yes, PLA can cause some issues in nature as it is acidic (lactic acid) and in quantity throws off pH balance in soil/compost, so many composters don't like to take PLA. OTOH, it is not a difficult problem to solve, and importantly, lactic acid is not inherently toxic in reasonable quantities (muscles generate it) and it shouldn't take too long for microbes to snatch it up once it is small enough.

To put that in contrast, typical plastics consist of toxic components that you do not want in your system, or even in your garden. They are mostly inert while intact, but they tend to slowly decompose and often leach even while in use.

Examples of compositions:

ABS - acrylonitrile (toxic at low doses [1]), butadiene (Group 1 carcinogen [2]), styrene (known carcinogen [3]);

PET, PETG: phtalate (Endocrine disruptors [4])

  [1] https://en.wikipedia.org/wiki/Acrylonitrile
  [2] https://en.wikipedia.org/wiki/Butadiene
  [3] https://en.wikipedia.org/wiki/Styrene
  [4] https://en.wikipedia.org/wiki/Phthalate

TIL. Can you tell me more about the recycling process for PLA?

Shred, heat and extrude.

Thank you very much. Not sure why my question was downvoted.

I do wish it were required to give a reason or comment to downvote. I upvoted you to compensate since the downvoter did not do this.

I would dearly love a world in which you provided a reason to download a comment on this site.

Wait, wait, let's not give the wrong impression. Yes, you can recycle PLA to an extent but you can't mix it in with your recylables. Few cities can recyle PS, much less PLA or at least they aren't set up to handle it.

If you are curious about the tech, sure, it's recyclable. For practical purposes you may as well throw it in the trash ahead of time and avoid contaminating the recycling. Plus if you try to put it in most commercial composting it will not degrade enough to be usable and has to get removed to avoid damaging the compost. So if you happen to not have the right kind of composting facility you can't handle it.

Yeah, it's on paper no worse than other plastics, but you have to have a plan to handle it -- it's not just a thing you can toss in the recycling bin.

PLA is pretty useless as a material though for anything but art. Almost everything I print has a functional purpose and either (a) needs mechanical strength (b) will be placed outdoors in the California sun or (c) will be used to house electronics that may reach temperatures as high as 70-80 C.

PLA is basically useless to me and pretty much all roboticists. I use PETG for almost everything because it works perfectly for all my needs; unfortunately I often need to go through about 2-3 versions of many parts I make and wish there were a better, more efficiently recyclable option that has the same or better properties as PETG.

If the part doesn't have to last long or is subjected to smaller forces and the robot is kept in a controlled place PLA is fine. We used them it to make parts for robotics competitions in college.

It really depends on what you're building. For controlled environments that's fine, but unfortunately I'm not building for controlled environments, and tend to do quite extreme things with parts. I need them to be subjectable to force and reasonable amounts of heat. There is no way around it in my applications.

Point is PETG works, sometimes I need to go to CF-Nylon, I'm just looking for something that's as good mechanically and can be recyclable. I wonder if the plastics in the article would work.

> It really depends on what you're building. For controlled environments that's fine, but unfortunately I'm not building for controlled environments, ...

Sample size fallacy right here. Just because it's useless to you doesn't mean it's useless. Plenty are doing fine with PLA.

I’ve just been living with the downsides of pla. Should I just switch to petg?

I have my printer in my bedroom though. Is petg toxi to breathe?

Not sure how toxic PETG is but the fumes are quite unpleasant. When I was around where large amounts of PETG were being worked with, ventilation was a must.

yikes, i thought 3d printers were high emitters of tiny plastic particles that are harmful to breath. Hope it's well ventilated

> I’ve just been living with the downsides of pla. Should I just switch to petg?

As far as utility goes it's so much sturdier as a material that I don't even comprehend why people use PLA, especially considering they are very similar in price, and it's much easier to work with than ABS since it is not particularly prone to warping. If PLA can realistically be composted though, that's another story, bu I was under the impression 3D print PLA isn't the same as compostable PLA cups.

> I have my printer in my bedroom though. Is petg toxi to breathe?

PETG is not known to be toxic, so it's a much better choice than ABS if you don't have a garage or fully ventilated area. That said, I'm always skeptical and I don't keep my 3D printer in my bedroom.

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