Non-recyclable plastic waste (V4)
Hey guys, my name’s Paul and I’m a designer working on PP V4. One of our focuses for V4 is exploring ways to use the non-recyclable plastics (NRP) that we often collect but don’t have a use for.
To be clear, I’m talking about plastics that have no hope of ever being recycled back into useful tools/products/materials. Plastics that have been:
– degraded due to extended sun exposure, saltwater, etc. (common among beach plastics)
– molded with other materials (metal, silicone, etc.) and can’t be separated for recycling
– are simply too dirty to be cleaned effectively for normal recycling
Typically when these materials are collected, they’re sent to the landfill where they waste away eternally, or they’re incinerated to produce energy.
Neither of these options are great… Sending NRP to a landfill means the materials that could be useful will do nothing but take up space in a big pit of waste. And incinerating them releases gases into the atmosphere that contribute to air pollution and climate change.
So.. Our mission is to give hope to the Hopeless. Sounds tricky, but I think we can figure something out. I’ll share progress in this thread. If you’re interested in this issue and would like to contribute thoughts, ideas, and constructive criticisms, they’ll be greatly appreciated
To start out, I’ve collected materials from the ‘Burn’ bin in our workspace – this is our last resort container where we put things that we can’t reuse/recycle properly.
Most of the plastics I found are molded/fused to other materials and can’t be separated (tape, packaging, ink pen, etc). Some are thermosets and can’t be remolded (silicone, rubber hose) and some are simply too dirty/degraded to be used in normal recycling processes.
There are a couple of directions I’m interested in exploring as a starting place.
One direction is Pyrolysis (plastic to oil), which transforms materials (including plastic waste) into oil which can be used for energy. There might be other uses for the oil as well…
The other direction is using NRP for building materials. In this way, the solution would serve as a long-term form of carbon embedment while simultaneously offering an alternative to environmentally harmful materials such as concrete.
Direction 1.0 | Pyrolysis: Waste to oil
Pyrolysis can be used to transform materials into oil which can then be used for energy. It might also be possible to synthesize the oil into a cleaner, more useful material with other applications..
1.1 | Alternative energy source to virgin fossil fuels
Transforming the NRP into oil could offer an alternative to virgin fossil fuels for communities that rely on fossil fuels for energy and don’t have access to renewables. In this way it’d help reduce reliance on virgin fossil fuels and simultaneously give purpose to the abundant material resource of NRP. Using the oil for energy would still emit greenhouse gases, but at least the energy source would be plastic waste that’s useless rather than newly extracted fossil fuels. Along with that, saving money on fuel could enable communities to save enough money to eventually transition to renewable energy sources. In this way, this solution could serve as a sort of stepping stone for some communities.
1.2 | Back into useful material
Once we convert the plastic waste into hydrocarbons (oil), we might be able to synthesize it into a cleaner, more useful material. If so, there’s a variety of purposes that the material could serve that would likely be better than what we’re able to do with it in its current state. Plus it wouldn’t be burned, keeping the carbon and other greenhouse gases embedded in the material rather than emitting them into the atmosphere. Not sure if this is doable, but seems interesting. If anyone has any insights I’d be keen to hear.
I’ve seen Pyrolysis discussed here before and am including a link to the earlier forum as well as some resources I’ve come across in my research so far.
– Earlier forum discussion :https://davehakkens.nl/community/forums/topic/small-scale-pyrolysis-plant-for-making-fuel/#post-132354
– Pyrolysis research article: https://www.researchgate.net/publication/281064326_CONVERSION_OF_PLASTIC_WASTES_INTO_LIQUID_FUELS_-_A_REVIEW
– DIY pyrolysis: https://www.instructables.com/id/Waste-Plastic-to-Fuel/
– Group developing open source pyrolysis unit: https://plasticodyssey.org/technologies/?lang=en
– Plastics-to-Fuel Report by Ocean Recovery Alliance: https://www.oceanrecov.org/about/plastic-to-fuel-report.html
– Plastic to fuel market review 2017: https://www.planning.act.gov.au/__data/assets/pdf_file/0008/1043657/Appendix-G-Review-of-Pyrolysis-Worldwide-RICARDO.pdf
– Intriguing case study, and links shared between @craig89 and @frogfall: https://davehakkens.nl/community/forums/topic/precious-plastic-in-the-scottish-highlands/
– @plaspod ‘s work with Pyrolysis: https://docs.wixstatic.com/ugd/52d1ea_187cf3d94bfc45688ed4ec5ce32afb5f.pdf
– Study on performance and emissions of pyrolysis oil: https://www.sciencedirect.com/science/article/pii/S0378382016307135
Direction 2.0 | Alternative construction material
This direction interests me because it could serve as a long-term method to store NRP in a useful way, rather than letting it simply waste away in a landfill. This direction is also appealing because it could serve as an alternative to ubiquitous, environmentally harmful materials such as concrete.
There are a couple of methods I’m interested in starting to explore that might offer viable solutions.
2.1 | Compression to form bricks
With this method, the NRP would be shredded and compressed into forms which could then be used to build long-lasting structures. This could be especially useful in communities where construction materials are limited, but plastic waste is abundant such as coastal communities and towns rebuilding after a natural disaster.
The tricky thing with this direction is that the materials being used will be mixed, so we’ll have to find a way to bind them reliably across all sorts of different mixture ratios.
One way that might work is ensuring that there’s a certain amount of PE in the mix (lowest melting point of common plastics), then heating the mixture to PE’s melting temp and using the molten PE to bind everything together. Or maybe there’s another binding agent or cold-compression method we could use… Again, any experience and insights are greatly appreciated
2.2 | Alternative to conventional concrete aggregate
Concrete, one of the most commonly used commodities in the world consists of cement and aggregate (or filler). Generally, the aggregate is a mixture of sand and rock, which is typically mined. Mining these resources inflicts serious damage on our planet (google ‘concrete mine’).
Using NRP as an alternative aggregate could reduce demand for these environmentally damaging materials and provide a method of storing NRP in a useful, long-lasting manner without releasing its carbon/toxic gases into the atmosphere.
The thing we’d want to be careful of is ensuring that the NRP concrete is used for static applications with low friction that won’t cause the plastic to slowly rub off and emit microplastics into the atmosphere. Buildings and furniture seem like they could be good uses. From what I understand, using the material in applications such as pavement, etc. could lead to problems down the road (hehe) with microplastics rubbing off and being dispersed into the environment, which is something we definitely want to avoid.
One concern that some V4 teammates have voiced while sharing the idea around the workspace is that mixing the plastic with cement might complicate the problem by adding a new material into the mix. My thoughts are that the NRP we’re using is already an unsortable mixture of plastics, metals, rubbers, etc. (part of why it’s non-recyclable) so adding cement would only marginally reduce the NRP mixture’s “purity”. Granted, it would add some complexity in terms of what exactly the concrete is made of, but as I understand it, once concrete reaches the end of its life, its best use is to be ground and used again as an aggregate base for new concrete, so it seems like having the NRP would be okay from my view. Keen to hear others’ thoughts.
Below are some resources I’ve found in my research so far:
Alternative construction resources
– Earlier forum discussion: https://davehakkens.nl/community/forums/topic/help-on-a-earthquake-rebuilding-project/
– Plastic waste compression molded into bricks: https://www.byfusion.com/the-blocker/
– Henry Miller’s research into using NRP as concrete aggregate: https://inhabitat.com/plastic-concrete-repurposes-landfill-waste-into-building-bricks/
– Article about NRP as concrete aggregate: http://useofcement.cembureau.eu/2018/04/09/cements-solution-to-plastic-waste/
– Plastic legos construction concept: https://www.youtube.com/watch?v=SR2N_USfFzE&feature=youtu.be
– Cement life cycle overview: http://www.designlife-cycle.com/new-page-40/
Seems there have been some weird things happening with this forum topic… apologies to all tagged if you’ve been receiving sporadic and/or broken emails referring to this post. I think we got it worked out… tagging those I saw throughout the forums who might be interested one last time to be sure
Glad to see you guys are looking into this.
This article has some interesting figures about adding pyrolysis products into building materials. The author focuses much on wood charcoal, but I suspect solids from the plastic pyroysis (aka carbon black) could have a role in improving concrete and plastic composites. Energy in the form of heat or liquid fuel could be extracted from the plastics prior to tying up the remaining carbon in building materials.
We run our heavy pyloysis oils through a babington style burner we modded from a conventional oil heater. We’ve also used these oils as an asphalt binder (tarmac) – our sample isn’t much to show for, but it’s held up for over 3 years outside now. I suspect raw plastic oils could be used in a similar process. Though I doubt we’ll be able to find a contractor that would let us use their equipment and scale up…
I hear alot about people saying they COULD make diesel/gasoline from plastic pyrolysis oils, but I don’t see much of it actually being done on small scale.
@pauldufour, great posts, thanks a million !
Precious Plastic has created a unique model that allows plastic to be re-purposed on scales that are beneficial to both society and ecology. That fact is an important driver!
The collective aim here should be to bolster and enhance that model with the addition of beneficial technologies (micro-scaled) that can support and sustain the development of social enterprise at community scales.
The images that follow have been taken from a ‘work in progress’ document. This document details the levels of energy used to collect and recycle certain types of plastic via current industrial processes (UK model). It also details an alternative community-based model, built around PP machines and Plas-Pod. This model does not include the production and use of pyrolysis oils and still achieves zero-waste.
We have determined the value of the waste to the community in terms of energy generated from non-recyclable plastics. We will endeavour to determine the carbon footprint of this model for comparison but would be confident to suggest that it will be more efficient than the industrial status quo.
Determining value to the community via the production of products will be more challenging. Selling high-grade plastic on to recycling companies has been included here as one option: other options, including manufacturing products that can embedded into the community will be added as the work progresses. The opportunity to develop a cashless economy is exciting but requires careful planning.
We need to ensure that the energy that we generate from non-recyclable plastic is used wisely (restricting waste). We can do this by producing electricity that we need to run the PP machines and we can generate the energy needed to heat the workplace over winter using the same process. This makes sense because it is the most efficient way to produce and utilise energy – at the point of use. Theoretically, this plastic becomes embedded into the community as well.
Added to this, we have made the Plas-Pod mobile, hoping that we can take it to various locations within the community to generate energy that can be fed straight into existing water heating systems: this would work well in schools, where reasonable volumes of waste plastic are generated. Reducing the energy costs for the community offers benefits to everyone in that community.
Key for us has been to develop smarter methods of heating and storing water. We are currently working with a team of engineers from Romania (where it can get very cold!) to develop a low-cost boiler which can run directly from the Plas-Pod machine. We don’t want to reveal the entire design until we are confident that it meets expectations, but you can see the test here –https://youtu.be/IHlxDLldnzw
The reason that we have tested to steam-point is because we have been working with a company in Holland (Green Turbine) to develop a unit that can produce super-heated steam to drive their micro-turbine to produce between 1.5 – 15kWhe.
We have more than 20yrs experience of producing pyrolysis oils, both as a primary product, via the Biogreen Technology (http://www.biogreen-energy.com) and as a co-product via several other methods of pyrolysis. As Dan suggests, we are also yet to see anyone making anything useful from these oils.
Our experience would be to steer others away from pyro-oils to focus purely on more efficient conversions to energy from non-recyclable plastic.
Respectfully – @plaspod
2.2 | Alternative to conventional concrete aggregate
Firstly thank you for tagging me into this conversation,
To contribute a little I completely support this direction and would like to make some points from my time in Eco Architecture.
This solution (2.2) is the easiest to implement from my experience compared to creating solid plastic blocks mainly because it utilizes basic technology that most countries understand fully, and are trained to work in (Concrete work). Concrete is based on ratios to acquire different strengths and those mixes can be edited to use different aggregates (no extra tools required). If clever we could also come up with a mix to make hollow blocks, using standard hollow block machinery.
Have you by any chance investigated Biocrete? (Hemp Crete, Coco Crete, or Rice Crete?) all substitute the 3/4″ gravel aggregate to utilize a waste fiber or material. In some cases, lime is also added, this allows the material to hold moisture. So that in tropical climates moisture is collected at night and evaporates during the day to create naturally ventilated buildings through evaporative cooling.
The fiber or waste also tends to provide a certain level of tensile strength, not found in standard concrete. This could be a good selling point when pitching the idea of inserting plastic into standard concrete to communities. Cheaper & Better….always a good pitch.
My only comment about plastic in this method of construction is that we would need to ensure that it is not exposed to the sun. Solar degradation will cause the surface layers to decay, and create a fine plastic dust. This can be avoided by plastering the surface layer.
While we are on the topic of utilizing waste materials, the island I am currently running our project on doesn’t have any glass recycling. Could we not take this one step further, Cement, fine glass (Sand), Plastic (Aggregate)?
Another method is Eco Brick, they use a standard bottle and pack it with NRP, however, this is very labor intensive, and most developing countries will stick to traditional methods with a limited adaptation of the method.
Keep up the great work, if you have any questions I’ll be happy to help.
PS. We are building a few walls in a recycling center in a few months, it would be great to pilot these methods if we get the facts straight. Then we can create an instruction video?!
Thank you for your thorough responses. Your input will be super helpful moving forward.
@lwfbiochar The article you shared about incorporating pyrolysis by-products into building materials is super interesting… the Biochar Journal as well as other resources that it led to are proving to be helpful for research as well. I’m very keen to explore the other applications that pyrolysis might be used for beyond energy production.
@plaspod Couldn’t agree more – Precious Plastic’s micro-scale is a key part of what makes it so valuable. Our goal in exploring uses for NRP is to develop ways that we can make use of the mixed, dirty, non-recyclable waste that we currently have no use for. As I understand it, a lot of communities simply burn the waste with no filtration system as a way of getting rid of it. Finding a solution that’s more useful than burning will help mitigate the negative environmental and personal health impacts for those living in the communities where this occurs. @mattia-io and I were chatting this afternoon and he mentioned that you guys have spoken previously about pyrolysis. I’d love to learn more about your experience and particularly what sort of plans you have moving forward with Plas-Pod. We’re interested in running some pyrolysis tests to get a better understanding of what the process offers. Is there any chance you’d be willing to assist at some level?
@rorydickens I agree with you that the simplicity of the concrete aggregate application would make it easy for communities to implement – in fact I’ve already seen some doing it. I haven’t looked into biocrete much, but am keen to check it out. Adding plaster to the surface of plastic-concrete to avoid solar degradation is a good thought. I’ve seen the Eco-Brick before and find it interesting. Aside from its labor intensity, it seems like a good use for this material. I wonder if there’s a way that we could streamline the process to make it more efficient…
Thanks again for your input and support.. More to come 🙂
Experiment 1.0 – Processing raw NRP using existing PP machines
After collecting non-recyclable plastic waste from our burn bin last week, I wanted to see if there’s a way that we can make the waste more useful and/or manageable using machines that we already have.
First, I ran most of the material through our shredder. Grinding the material up makes it more manageable to store, which is nice. It also opens up some possibilities in terms of molding. There may also be ways to use the material in its grain form.
One downside of using the shredder for this is that the mixed materials made the machine quite dirty (and unusable for other purposes) so afterwards I had to disassemble and clean it before it could be used again for normal processes. The messiest materials seemed to be the packaging and tapes that used glues/adhesives. After a while the glue built up on the blades, causing material to stick to them.
Some items were simply too messy to run through the shredder, such as caulking tubes which had leftover material in them.
As a quick test to see how the materials would bind together on their own without adding a binding agent, I molded them using the compression machine, which resulted in a substrate that holds together reasonably well… results will obviously vary depending on the mixture used. For some reason there was quite a difference in appearance between the two sides of the substrate. Guessing it’s heat-related.
I’m curious to learn how much of the material’s binding success is due to melted plastic, how much is due to pressure, and how much is due to the glues mentioned above. I’m also curious to see how it performs in a thicker block form (as opposed to sheet).
What temperature do you use for melting – it is a very difficult find appropriate regime because of different types of plastic?
I wonder if there’s a way that we could streamline the process to make it more efficient…
Im thinking either an injection style machine that allows the bottles to screw on while they are filled or something more manual like this Columbian idea?
@pauldufour Fantastic work! I’m also starting to think and tinker with mixed, dirty plastics as it is much harder for me to find sufficient clean plastic that is affordable where I am.
“I’m curious to learn how much of the material’s binding success is due to melted plastic, how much is due to pressure, and how much is due to the glues mentioned above”
Have you been able to draw any (even speculative) conclusions about strength/quality vs pressure, adhesives, and melted plastic “glue”?
I’m very much looking forward to keeping up with your progress!
thanks @nickchomey 🙂 looks like you’re located in argentina if I’m not mistaken?
I’m planning to dig deeper into learning about material properties in the coming weeks and will keep you posted.
do you have any pics of the dirty plastic you’ve found troublesome? I’d love to see what kind of materials you’re working with
Experiment 1.1 – Processing raw NRP using existing PP machines
To build on my last experiment, I compression molded a larger amount of the same non-recyclable plastic mixture which resulted in a block that’s 4cm thick. I haven’t run any tests to measure exact strength, but by touch the block seems to be quite durable.
Moving forward, I’d like to collect a more diverse selection of NRP (beach plastics, dirty plastics, etc. outside of our own workspace) to run compression tests comparing material properties of the different materials and mixtures to see how they vary. These experiments should give us a better understanding of the potential uses and applications for this category of plastics.
Very interesting. I haven’t made anything quite yet, but am planning to try to build houses out of recycled plastic here in Guatemala. There’s plastic everywhere and it can be bought pre-sorted by type fairly cheaply in any quantity at the “recicladoras”, but I don’t have any high volume shredding capability as of yet. So, I can buy it well shredded for about 3-4x the price, and a bit more for washed (I’m skeptical of how clean it will be given the marginal price increase – I’ll have to test it when I buy some soon).
Anyway, if I can build things of reasonable quality with dirty plastic, it would lower the cost. And would also make it more feasible to source raw plastic if all that’s required is to shred and melt it – i just assumed that it wouldn’t work very well if dirty. I suppose truly dirty stuff – e.g. motor oil – could be pre-screened, and only use plastic that is simply dirty or has other residues and adhesives on it. After all, most of what I’ll make won’t really be “structural” so much as just sheathing or furniture. The important pieces could be made with more “pure” plastic.
Plenty to keep experimenting with! I should be starting in the next couple weeks once another project comes to a close.
I look forward to following your progress!
I think you are the best person to ask the following:
We collect household waste cooking oil and get the oil mainly into PET bottles (see picture). Our idea is to build a shredder to separate the plastic from the oil.
Now, the question are:
– will the shredder be damaged by the oil and all the dirt that come with the oil?
– what to do with that plastic? What would be the best use? I understand that it would be too difficult to wash it..
As long as I know at least in my city (Barcelona) the plastic from copper wires is used to this spacers which allows bikes to ride freely.
If you use stainless steel to build the shredder, it should be ok with oil and dirt as long as you take the time to clean it properly when needed, which will probably mean disassembling it every so often to ensure that the parts are completely clean.
With regard to your second question – it’s tough to answer from afar. Are you asking what to do with shredded PET bottles after separating oil from them? If all they have is oil, they shouldn’t be too difficult to clean using a soap/water mixture. PET is very challenging to recycle though, so in my opinion it’d be best to reuse the bottles as they are rather than use energy/time/resources to recycle them, though without knowing more about your project it’s hard for me to advise much beyond that. Hope this helps – feel free to reach out with any other questions 🙂
Experiment 2.0 | Low-tech pyrolysis
Switched directions a bit and began to explore the possibility of using a low-tech pyrolysis unit to process NRP. It seems like it could be a good way to transform the unpredictable, unsortable mix of NRP into a more predictable, more uniform material that could either be used as an alternative to virgin petroleum fuel sources or potentially synthesized into a useful material that can be used for building/making.
I began by building a very simple pyrolysis unit based on this instructables https://www.instructables.com/id/Waste-Plastic-to-Fuel/ included below is an oversimplified illustration to explain the general process.
To start, I used an IR thermometer to read the temp of the chamber to make sure it’d be hot enough using a propane burner, but realized the reading might be inaccurate due to the chamber’s shiny metallic surface, so I painted the chamber with a heat-resistant paint that can withstand up to 800 deg C. The paint burned off, so if the product claim is true, the reaction chamber was at least 800 deg C.
As a control, I began my experiment using 300g of clean polypropylene – this way I’d be able to know that the unit was working. Once proven, I’ll begin using NRP. My initial 2-clamp design wasn’t enough to keep the chamber air tight and there were a couple of leaks in the weld.
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