Washing Plastic (V4)
Washing plastic is essential in the recycling process and at the moment it is mostly done by hand – a very time-consuming process.
While working with plastic films I came in contact with water and plastic and the advantages but also dangers it has to offer. Shredding film has turned out to be a challenge because of overheating and dust. My only solution for this was to work with a water-cooling system. I got familiar with the dangers of microplastic in water, the dirt and chemicals, and filtration processes. I changed my focus and now I am working on everything which has to do with washing. Starting before shredding and ending with a clean and dry workable material.
Washing plastic is a very broad topic and it contains many different steps. Each of them is important and I will spend the next months on researching, experimenting and updating you guys – I hope, together with your help, we can create a way to make it possible, that small workshops are able to work efficiently and save for the environment.
Creating clean plastic demands different machines, which have to function in a workflow. Designing this process seems to me as important as designing the machines so I will also work a lot on how the different work steps could look like.
So what have I done so far:
After gathering all the information from @mathijsstroobers topic washing plastic and some research I have defined and started to work on the different steps – Cutting and prewashing, shredding with water, collecting the shreds in a mesh bag, modifying a washing machine, drying and most important filtering.
Cutting and prewashing:
I haven’t done any experiments here yet, but I believe for some sort of products it might be helpful to clean them a little bit before shredding, e.g. oily surfaces or impurities like sand which would be to rough on the shredder. Though the end goal is to make this step obsolete.
Shredding with water:
This is a fairly easy process, as long as your shredder is built from stainless steel or made water-resistant in any other way. I connect a pump (link here) to a water tank, located beneath the shredder from there a pipe leads up to the shredder and the water cools, contains the dust and ends up in the tank again. Of course, you need some sort of sieve or mesh to keep the plastic shreds out of the pump. In my first system I used a fine mesh on the bottom, this way turned out to be prone to failure and clogged up easily.
Collecting shreds in a mesh bag:
For the next system, I am trying bags made out of mesh. They will be connected directly to the shredder, collect the plastic, but let out the water and the dirt. For these bags, I am trying differently sized mashes to see what works the best for what kind of plastics and shredders. Changing to bags can help to keep a necessary cleanliness, they are used from shredding to washing to drying and also for storing.
A color system could help to keep the individual bags dedicated to one certain kind of plastics.
Modifying a washing machine:
A household laundry washing machine provides me with many features I can take advantage of. I can use the different programs, temperatures and especially the centrifugation function, which will help a lot to get the plastic dry after its clean. All whats then still necessary is to hang up the bag for a little bit and the plastic is ready to use. Connected to a water pump and tanks the machine manages to run autonomous and I can contain the dirt and microplastic in a filter, before adding the greywater to the sewage or even water plants. To save energy and reduce material damage the pump is controlled by a relay which turns on when the inlet valve of the washing machine opens up. How effective this process is gonna be I still have to find out in the next weeks with many experiments and ways to proof the cleanliness of the plastic.
This is probably the most challenging, but also most exciting problem. The plastic we wash is very contaminated with dirt and oil and also loses microplastics in the process. All of this will end up in the water. Many low-key washing facilities around the world are pouring this toxic mixture on the streets or in the sewage, a proper filtering system can be very complex and expensive. I am going to gather information about ways to filter different contaminations, recreate them in a DIY environment find out what works and at the end provide instructions for an easily repeatable filter, so workshops can deal with their own waste.
The first two prototypes are connected between the pump and the dirt-water, this is not an ideal solution but I am trying to work now with one “clean” tank and one dirty one. Perhaps I will introduce an overflow filter between those two.
The filter medium I chose is polyester filling. In my test, I got very good filtering results and the medium can be used for a long time (so far). After it is unusable, we can dry it and for example, put it in a pyrolysis machine or bring it compactly stored to a recycling facility. Attached to the recent filter is a box with activated charcoal to reduce the toxins in the water, this is a very well tested way and I only need to figure out how often I should be using it to get out the most of the activated charcoal.
Each topic is covered only very vague and I will post more detailed later about them, but right now I am testing, researching and could really use some input about your experiences with cleaning plastic, filtering water, drying and everything around. One problem for me at this point is to find good methods to control how well I am able to clean the plastic and the water. To see the results in plastics I will start with one very simple method. In a small mold, I press and the test sample in a sheet of roughly 1 mm thickness and control it over a light table for seeable contaminations, how I can find oils and other alien materials is still a mysterium for me. A similar process can be used for the water.
If you have tips, questions, critics please answer in the topic and I will get back to you!
I’ve been exploring uses and solutions for non-recyclable plastic over the past couple of months for V4 (see more here)
A lot of the plastic I’ve encountered hasn’t truly been “non-recyclable”… we just don’t have an efficient way to clean it properly right now, so it ends up being discarded rather than recycled. I’m teaming up with Louis to develop a cleaning method to take care of this problem.
Experiment | Cleaning unshredded plastic waste with washing machine
To start off, I experimented by collecting dirty (moldy), household plastic waste to see how well it’d be cleaned in the washing machine without shredding beforehand.
Below are some images of the results. The plastic was partially cleaned, but some residue remained on many of the pieces.
Conclusion: Leaving the pieces in their original form seems to be less effective than shredding (at least when contained in the mesh bag) since it makes it more difficult for the water to reach every surface. Smaller pieces got trapped in larger containers which also caused complications.
Experiment | Using a paint mixer to clean shredded plastic
This morning I experimented with using a multi-purpose mixer to clean shredded plastic in a bucket of water.
The mixer creates a lot of turbulence, which seems like it could be pretty effective for cleaning plastic. The mixer’s turbulence seems like it’d be a good counterpart to the centrifugal force created by the washing machine, which is better for forcing particulate/water out once it’s already been agitated.
Switching back and forth between rotation directions seems to be a good way to continually agitate the plastic. You could potentially have 2 or 3 mixers installed into a single, large container, rotating in opposite directions to really stir things up.
Louis and I discussed the possibility of a two-phase process earlier and it seems like the mixer and washing machine might be a good combination for such a process.
Phase 01: Use turbulence of the mixer to agitate and aggressively clean/separate particulate from plastic.
Phase 02: Use centrifugal force of the washer to force remaining particulate and water out of the mix through a mesh.
More experimenting to do, of course, but interested in exploring this route – In this scenario, it might even be possible to simplify the washer down to a rotating drum that’s rigged up to some sort of motor/bicycle.
To get a better understanding of how well the mixer worked, we collected some dirty plastic waste from local dumpsters – a majority of the waste was contaminated with food. We found a large amount of the same type of dirty plastic (white plates w/ tomato sauce) so we decided to use these as a control for our first tests with the mixer.
As a starting point, I selected plates with a range of dirtiness from pretty clean to very dirty to see if there’s a limit to the mixer’s effectiveness. Some of the plates had a lot of contamination so I put them through a mix cycle prior to shredding them in hopes that it might remove some of the large, loose contaminants. This method turned out to be a good way to remove loose contaminants prior to shredding, however it did result in some plastic shreds being created and left behind in the water (the plates were extremely thin – i don’t think this would be an issue with thicker plastics)
Once the plastic plates were rinsed, I wet-shred them (shred them while spraying water into the shredder). Then I mixed the shreds in a bucket for a total of thirty minutes, removing samples at five minute intervals in order to learn how much time is needed to effectively clean the plastic with the mixer. After 30 minutes, I washed the remaining plastic in a mesh bag in the laundry machine to see how it’d compare.
The biggest observable differences in cleanliness are between the shredded but uncleaned plastic and the five minute mix – There seems to be a diminishing return once you past the five minute mark. There was also a large difference between the 30 minute mix and the laundry cycle. The laundry cycle brought the plastic back to a bright, vibrant white, which the mixer failed to do.
Experiment | Using a sander to agitate
Another method we experimented with was agitation using the vibration of a sander – we made a quick and dirty prototype by strapping an old sander to the bottom of a bucket of water. The sander agitated the water quite a bit, however plastic remained dirty after ~15 minutes of agitation.
Experiment | Testing various methods with various types of dirty plastic
Next, we tested the various cleaning methods on different types of dirty plastic to see if there’s a “one-size-fits-all” technique or if different types of “dirty” require different cleaning methods.
Cleaning methods used
– wet shred
– warm laundry cycle
– cold laundry cycle
– drill mixer
Dirty plastic types
– household: food contamination
– commercial kitchen: oil, etc.
– beach: sand and algae
Warm laundry cycle did the best job of bringing the plastic back to a bright, vibrant white. Cold laundry and the drill mixer results were pretty similar to each other which leads me to believe that warm water is an important variable for cleaning this type of plastic.
Warm laundry cycle was the only method that removed the oily residues from the plastic. Warm water seems to be a very important variable for this type of plastic as well.
Sand remained on the plastic after using all of the listed methods. That said I did find the sand very easy to remove by lightly scrubbing the pieces pre-shred with water and a brush. None of the methods completely removed the algae, however the warm laundry cycle did a better job than the other methods.
Warm water seems to be a pretty important variable in order to completely clean the various types of plastic, however for certain cases where complete cleanliness (brightness, etc) isn’t necessary, cold water can work. From these tests, it seems the warm laundry cycle is the best method to effectively clean plastic. In cases where laundry machines aren’t available, the drill mixer could be a good low-tech alternative.
You don’t speak about any kind of washing additives. When you have greasy stuff on your plastic (eg foodplates) an emulgator (soap) is efficient to bind water and grease.
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