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Soft-plastic recycling – research and feasibility

Marc Vruggink marcvdv

Soft-plastic recycling – research and feasibility

16/05/2019 at 11:08

Dear Precious Plastic community,

I am intern in Swiss research institute working on waste management. A waste audit in one of our nepalese case studies highlighted the need for treatment solutions for soft plastics (mainly food wrappers, approximately 10kg/day). For the next two month we will  be conducting a research in Nepal on Small scale soft plastic recycling.

Among my tasks, I’ll be working with a local NGO to achieve and document the construction of a compression machine.

I’ll keep you updated on our progress through this post and I’m happy to hear about your suggestion, experience, comments, etcetera.

Suscribe to the post to stay updated!
All the best,
Marc

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warrior
30/05/2019 at 19:11

@marcvdv , I used our kitchen oven a couple of times for experiments. Even with the windows open and a fan on, the fumes were an issue. I’ve stopped using that oven for that reason.

Hopefully you have several temperature sensors/readouts you can use during your experiments. I found oven temperatures vary significantly. Are you planning to use your own controllers? I would sill consider adding a fan of some kind.

Those range top heating elements may be useful for directly heating molds.

warrior
30/05/2019 at 13:59

Or paper (with some modifications).

Or the actual answer, which is ‘bean burgers’, but hush, don’t tell anyone!

 

‘Extruder’ is fully metal, so would be interesting to try…

Gotta love vintage tech!

warrior
30/05/2019 at 13:47

LOL 😉
If it doesn’t work for plastic (are you going to heat it?), then it can always be used for food…

warrior
30/05/2019 at 13:39

@frogfall

Also got my first extruder!

Any good, you think?

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warrior
26/05/2019 at 19:47

This is the shredder I used on the coffee & linseed wrappers. It is quite old, and was acquired for free a long time ago from someone who had bought a better one. The rating plate says 220-250v ~0.5A 50Hz, and that it shouldn’t be run for more than 2 minutes without a 30 minute cool-down. It was made in China.

Conversely, where I work, we have a large document shredder that can also shred DVDs – so much more powerful machines do exist.

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warrior
26/05/2019 at 19:13

@marcvdv

Excellent point. Washing and shredding!

 

I actually once build a multiple blade office paper cutter, because I had to cut a lot of same size lamminated badges out of a printed roll (with space in between them).
Did work, but if you don’t need ‘same size’ you’re way faster just chopping them up with one cutter.

I’ve also tried to cut thin foil with an office cutter (for shrink wrap packaging).

Foil just folded over the edge, along the knife (unless you close it really fast).

 

A build like this might work better (with some tweaks (like using razor blades)):

Could also be hand cranked…

 

 

starter
26/05/2019 at 18:58

Yep, wet blending could be an alternative and could be combined with the washing step.

I was also thinking about something as an office paper cutter with multiple blades to shred our soft plastic.


@donald
About infrared, that’s the benefit of still being a student. I’ll try to document different alternatives for optical identification. But it doesn’t seem there’s a really low cost one.

warrior
26/05/2019 at 18:53

Addendum:

I was just in my shed and I saw my sledgehammer.

I think I solved the problem of shredding my old dvds 🙂

warrior
26/05/2019 at 18:08

@s2019

Exactly.

Motor, (magnets,) rotor, figure out the optimal container shape for the optimal flow and see what happens!

Worse case it only works with tetrapaks, but that would already be a big plus!

 

warrior
26/05/2019 at 17:55

An  infrared spectrometer… I should also get me one of those… bit expensive though…
Are there any simple alternatives?

I also wonder if it would be possible to build a bigger (tetrapak) “blender” vs shredder, as this might also solve the problem of other ‘mixed’ materials, like dvds and cd if you upscale it, and would possibly need a lot less power, and way less complicated ‘knives’.
A lot of (mixed material) recycling plants seem to use a ‘wet’ process anyway, so why not try?
A blender is kind of a vortex generator, so it could also help with the seperation of the materials… within the same machine…

 

I’m just thinking out loud, but I kind of have a vision of a ‘solar powered’ wet plastic blender, that works slow but sure (off the grid), is easy to build and maintain,  and would cost a fraction of the industrialized shredder, both in build and in use…

 

 

warrior
26/05/2019 at 08:45

Hi Marc,

I’ll see if I can find some building plans, but it should be pretty straightforward, as illustrated with this build:

“Just don’t touch it when it’s hot” lol

 

Searching for ‘DIY powder coating ovens’ should also give plenty of tutorials, maybe even specific to the kind of ovens you have access to.

Recycling the isolation from the old ovens would give the new build a much higher capacity (up to 400C, after which the isolation will melt) as DIY Powder coating normally maxes out at 200C.

 

 

 

starter
26/05/2019 at 07:55

Hey @donald,
Thank you for your answer. I will discuss with my colleague but I think building the box would be the best plan B.

As it is the first time we built the machines, I would be happy to read what you potentially have in your archives.

All the best,
Marc

warrior
26/05/2019 at 07:18

Should be possible, as you have a makerspace, to combine a couple of smaller ovens into a larger one.

Or maybe even to build something custom out of them to specifically fit the project.

 

This might meta-solve the problem, as Nepal is probably not the only community with only small ovens.

 

I have seen it done before. If you like I can dive into my archives to see if I can find more info, but the ‘make’ should be pretty straightforward.

 

As for the heat uniformity, as I understand it, you should replace the heat controller of any oven anyway. As the ovens you are using are smaller they won’t have that much of a heat buffer to even out temperature fluctuations, so these fluctuations will be more extreme, and thus more dangerous.

 

In short: I’d say Build the box!

 

starter
07/01/2020 at 11:12

@jamyb we sure don’t mind additional visibility 🙂 where can I find this collection?

starter
06/01/2020 at 13:02

@sowyourseeds yep, we tried a lot of it. Sorry, I’m on my phone so it’s not easy to transfer, but attached are some of the results we hadSometimes, even with alu. Layer, it melted and compressed easily at 218°C (be carefull with fumes though, we only tried on samples).

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starter
06/01/2020 at 09:52

@sowyourseeds I have built extrusion, injection etc from Dave’s design. I am from Maharashtra.
Yes I do have access heating elements, PID etc.
I have built machines for others before.
Can I DM you?

starter
06/01/2020 at 09:25

Yes, parle and also Britannia i see quite a lot whem it comes to bisquits.
A lot of food wrappers have that aluminium layer on the inse/outside, i imagine them to be quite hard to recycle, you tried some of that as well @marcvdv right?
We also have a lot transparent plastics, that is used for breads etc. Not sure yet what its made of but could be Polyethylene.

@sagar-sharma-2
awesome, where are you located? We are looking into building some machines ourselves (compression machine) but also would consider letting someone else build some machines for us, depending on price and shipping costs.
What machines can you build?
Do you have access to the heating elements for extrusion/inhection machine and Thermoregulation electronics?
Cheers

warrior
24/08/2019 at 19:47

@marcvdv , just curious, how did you project conclude? You took on a pretty tough task with limited resources.

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