School Project Turns Plastic Waste Into Bricks

Many plastics are, in theory at least, highly recyclable. Unfortunately, in reality, most plastic ends up as waste instead, harming the environment and providing no ongoing value to society. Wanting to investigate possible ways to repurpose this material, [Rehaan33] built a rig to create bricks out of waste plastic for a school project.

The aim of the project is to take waste plastic, in this case high-impact polystyrene, and reform it into a brick that could be used as a low-cost building material. The material is shredded, before being packed into a steel mould and heated to 270 degrees in an oven. As polystyrene is a thermoplastic, it can readily be heated in this way for reforming without harming the material’s properties. Once heated, the mould is placed into the press rig, which uses parts of an old drill press to force down a steel plate, helping shape the final form of the brick.

While you’re unlikely to see old soda bottles used to build a skyscraper in New York any time soon, such techniques could be a good way to help eliminate plastic waste in impoverished areas and stem the flow of plastic into the world’s oceans. The project served as a useful learning experience, allowing [Rehaan33] to pick up skills in metalworking, machine design, and working with thermoplastics. Recycling plastics is a key area of interest for many, particularly in the 3D printing space, with many exploring ways to reuse thermoplastics in more efficient ways. If you’ve got your own project turning waste plastics into useful material, be sure to let us know!

66 thoughts on “School Project Turns Plastic Waste Into Bricks

  1. I’m very skeptical on using plastic bricks as a building material from a fire safety point of view let alone the material properties. And selling an unproven concept as a benefit for “impoverished areas” is just the icing on the cake.

    1. plastic parts are mostly used for thin shell components, but waste plastic should be considered as a bulk material,
      in the 70s we used banbury rubber processing machines to recycle plastics, although bricks may not be the best use, I am sure there are many uses for all the plastic now being dumped in land fill and at sea,

    2. The rest of the material properties are more likely to cause issue IMO – sure plastics can burn, but a big mass of plastic like that with smooth faces its actually going to be hard to ignite properly. And its not like the timber and furnishings in many houses are particularly fire-retardant either.

      Used right this concept for plastic waste could really work – though I think to be effective it probably needs to be CO2? bubble filled expanded bricks for the insulation value, rely on the steel/timber/concrete beams for the structure and fill the voids to make well insulated walls – once the outside faces are rendered it will be very hard to make it burn – and if you made it froth up with something bicarb that breaks up into CO2 with heat the bubbles inside are going to try and smother a fire as soon as it starts..

      1. You’d be essentially creating an intumescent plastic brick. Interesting idea. With a few additives it could be interesting. The problem is then not the combustion per se as it is the temperature. The plastic will soften and melt, even if the bicarb keeps it from burning directly.

        Still worth a look IMHO.

      2. I would like to see this made into 3V and 5V panels for dome home building. with the gas filled holes then spray shotcrete inside and out. this would then make a home that is fire resistant and could withstand F5 storms for like the plains and coast areas.

      1. This brings to mind its possible use as a matrix for composite materials, either with thermosets or a dimensionally stronger material. If, instead of bricks, it were rolled out into corrugated sheets, it could likkewise be sandwiched to form a variety of semi-structural components. Regardless of form factor, operational temperature range may limit applications, and disposal at end-of-life will still be problematic.

      1. Wood is resilient in a fire because it chars, which forms an insulating barrier that slows down the combustion and the structure stays up for a long time even when it’s burning. Certain wood laminates which take this into account with fire retardants are actually holding up longer than steel beams.

        Plastic softens and melts well before it burns, and your walls would start to come down well before the actual fire has spread there.

        1. Not to mention the fact that the smoke released by burning plastics tend to be highly toxic compared to wood smoke, making it even more unlikely that any occupants will survive a house fire, and potentially endangering fire fighters and neighbors as well.

          1. It’s a given that plastic can release a host of poisonous chemicals upon combustion, but it seems to be CO that is the most immediately dangerous gas released by fires, and that’s a hazard with wood fires as well. I actually can’t recall hearing about people being killed by anything else during fires.

  2. Plastic bricks sounds like good recycling.
    But question is if it will actually be useful.

    Considering that plastic truss works for bridges were once believed to be the hot new thing for shorter spans. (Microplastics is though the big issue. one reason that California has banned Styrofoam in use as packing material. (And I think we all can agree that Styrofoam disintegrates into a bazillion parts at the slightest touch…))

    Though, as a neat way to compress and solidify plastic into manageable and easily stackable ingots is an advantage.

    1. If you add enough sand to PS chips before heating and forming a brick – you will get pretty usable construction material. And you could manage it like usual bricks, just don’t build a stove with that bricks.

      Also, you could change a mold and make a polymer-sand floor tiles perfectly usable in a backyard.

        1. Plastics as a surface that needs to be resistant to wear isn’t really ideal due to that alone.

          One might not care much for it personally, and the effects are long term.
          But that doesn’t make it a good idea after all, just like so many other things.

          One can make exceptions in areas where low friction is desired, but low resistance floor tiles sounds more like a prank than practical.

        2. The problem is macroscopic pieces, because the enzymes that bacteria use to break down plastics work on the ends of the polymer chain, and in a larger bulk of material the ends are not exposed. The smaller the particle, the more likely it is to find an end of a polymer chain at the surface, and the faster it is to break down biologically.

          Once you go down to microscopic particles, they really don’t survive for many seasons out in the wild. It’s actually somewhat likely that your powdered plastic and sand brick will be eaten away in a couple years and falls to dust. At the very least you have to keep it dry, or fill it up with some sort of poison like they do for pressure treated wood (which also sheds toxic microparticles).

          The confusion is that the category “microplastics” is defined to contain particles up to 5 mm which are not microscopic but simply small pieces of plastic. These are the problem particles, because they’re not yet at the size where they would be readily consumed, yet they are eaten by organisms that can’t digest them.

          1. And micro plastics is containing any “plastic”.

            So anything from PLA to PTFE and almost any other polymer in between.

            PLA being an ester that gets eaten away by most microbes is rather quickly broken down out in nature, it even gets absorbed if implanted in human tissue. (PLA is also used medically as a support material, and its ability to slowly get eaten away means that the body slowly gets to handle more of the burden, making the transition less sudden and easier on the patient.) Though, place it in a dray dessert and it will likely linger for decades….

            While PTFE is a fluorocarbon, it doesn’t really degrade due to its strong internal bonds and fairly exceptional chemical resistance.

            Where PET is on the scale is a good question, at least it isn’t as chemically resistant as PTFE.

            Though, the definition “microplastics” should probably be lowered from 5mm to something smaller.
            5mm is after all rather huge “particles”, it is fine gravel if it were a stone. Not yet down at sand, not to mention clay…


    1. It’s mess free for your home. No beads running on the loose. But imagine what happens after year of exposition to UV light and being beaten in stream or waves. It will turn into microscopic plastic dust, which is less buoyant, so can go deeper. And is impossible to filter in large quantities.

      1. So… paint it for UV protection.

        And when you are done with it either recycle it again or landfill it. Don’t throw it in the ocean or leave it to be washed into rivers that eventually would take it there.

    1. Throw some plastic into your fireplace. See what nice smells and smoke it produces when you burn it :) . See how your Neighbors like it :) .

      The brick idea is neat for compact storage and transporting though for recycling… But you do need energy to ‘make into’ bricks, so not free.

      1. When burnt at the right temperatures ( over 1000 C ) , polystyrene burns into mostly CO2 and H2O, plus some residues of the strange additives.

        Of course not all plastics work the same way, but each kind can have some more adequate disposal than others. And in the right conditions, the burning of polystyrene releases enough heat to be used as auxiliary fuel.

        1. When not “burnt at the right temperatures,” polystyrene releases large amounts of acrolein, which is pretty toxic.

          I did something like this using a trash compactor I dug out of the recycling centre, and a large propane torch to heat the compression chamber. I used milk jugs (HDPE), and used the resulting bricks for paving stones, rather than as a structural building material. HDPE is much more stable and way less toxic than PS, but you need a higher temperature to melt it.

      2. There are many ways to burn things. Some are better at complete combustion, some are worse. I have both a fireplace and a wood pellet furnace for heating my home. Furnace burns much more efficiently and there is much less ash, also probably much less of those small particles which make smog. Even in fireplace pellets burn much more efficiently (almost no smoke). There are already furnaces to burn various hazardous materials and I’ve heard about regulations about what is required for safe burning of various plastics (like minimum time of fumes being in burning chamber).

    2. 1) Always be careful when burning plastic, amny styrene-based plastics produce an impressive array of toxic fumes when they burn. It’s mostly an issue of which additives are present, but those often include things like phosphorus and cyanide compounds.

      2) Styrene, effectively a poorly-balanced hydrocarbon, will produce *thick* black smoke. This can be useful. When I was young I sailed a lot, and many of my friends would keep some big chunks of styrofoam stashed below on their boat.

      In case of emergency, they could be set on fire and floated downwind as they burned off, the thick black smoke plume would attract attention at some distance, a locally-recognized distress signal.

    3. Burning the plastic will return its carbon to carbon dioxide thereby contributing to global warming. The carbon in plastic had been sequestered, as petroleum, for eons. It’s better to return it to the earth as landfill.

        1. Great! So, we’ll ban all meat and dairy production, put WW2 style rationing in place to reduce calorie consumption in developed countries, and turn all the freed land back into sustainably managed forestry and wetlands for carbon sequestration.

    4. You might enjoy reading this NatGeo article (soft paywall, turn off javascript):

      I leave that here because the conclusion backs up my point: burning plastics is obviously not a renewable source of energy. If we built plants to burn them for energy, that is acknowledging that we will have a sustained stream of plastic “fuel” to make the initial investment in the plant worth it in the long run. I think that is not the best of idea because it to some extent makes an incentive to generate plastic waste. Right now we’re finding ourselves in a bind because we were sold the line “It’s okay to use plastic, it’s recyclable” but we’ve found out that was way overblown in it’s efficacy.

      1. > If we built plants to burn them for energy, that is acknowledging that we will have a sustained stream of plastic “fuel”

        That’s assuming plastics is the only thing they can burn. A waste incinerator can burn pretty much anything, so you can put the plastics in through the waste stream – and when there’s less plastics, there will typically be cardboard and paper, wood and cellulose materials, to substitute it.

        For example, if plastic bottles are replaced with waxed cardboard, you still have roughly the same amount of material coming in to burn. If instead of polyester shirts, you wear cotton shirts, you still have the shirt to dispose of when it wears out. Arguing that the waste incinerators would run short of fuel is assuming that we’d stop consuming entirely.

  3. Plastic for construction material usually falls prey to two problems – flammability and viscoelastic deformation. You can add fire retardant but you definitely don’t want bricks, beams or structural elements that will sag or squish over time. Recycled polyethylene is already used to make plastic “lumber” for things like decks, porches and benches though.

    1. That plastic lumber with wood mixed in has to be supported very well so it doesn’t sag. One brand that’s made the same sizes as normal nominal dimension lumber (some of their ads show fancy decks with it bent into curves) has a weathering problem. After some years of exposure the wood particles near the surface swell up and weather away, leaving the surface rough and pitted.

    2. Add expansion rate to the problems? Ever used pvc or composit lumber or seen vinyl siding put on too tight in cold weather? How will these expand / contract with weather? what will bond individual bricks to each other? I believe biggest problem was mixed resin waste at manufacturers, but that may have changed in the last few years, Might be good enough to replace loose laid landscape brick depending on if plasticizers leech out over time…

  4. The plastic is being repurposed not recycled. If it were recycled it would be broken down into chemicals that could be used for other products with hopefully no polluting or dangerous by-products. The only thing missing with their concept is the three round bumps on top that feel so good when step on them in the dark ( and cause you to create new swear words 😂 ).

  5. In Australia we dig up carbon and send it to China and then they send us other forms of carbon that we then use to fill in the big holes we made in the first place. Not sure exactly how the carbon capture equation works out in the end but we can always dig it back up again because we know exactly where it is.

  6. A few years ago, a local recycling company had the clever idea of molding recycled plastic into normal-size bricks shaped exactly like Legos, with 8 bumps on top, and 8 mating holes on the bottom. They sold them as toys; kids could build forts, play structures, park benches, and other temporary structures. The color tended to be random and full of swirls and patterns (whatever happened to be in the mix that week). But that doesn’t matter for non-serious uses.

    Alas, they were too much like Legos. They got a cease-and-desist letter from the Lego company and had to stop.

    But it was a great use for recycled plastic. I keep wondering if some entrepeneur could make a “toy” plastic molding machine so kids could make their own Legos out of the family’s plastic waste.

  7. ”” What a wonderfull idea ”” ..
    There is more than enough plastic and synthetic materials in ”’ modern ”’ buildings .
    ”” What a great idear ”” Just look at all the fatal fires there have being in buildings
    trough the years … shure a ”” great idea ””’
    Hm… maybe a good idea to find another use for this plastic .
    Recycling is good , but NOT as building materials .

  8. There seems to be a fixation on building is only possible aboveground surrounded by air in CA-like flammable areas, but huge plastic bricks would make great insect proof water proof buried footings for buildings. If the dirt seven feet down (in deep frost depth areas…) is over 500 degrees or on fire, you already have serious problems that merely using concrete will not fix.

  9. “low-cost building material”

    Um, this quality of polysteren scrap sells for about $1200 per ton (alibaba), so since its weight is actually 1 kg, that’s $1.20 per brick, in material.

    Just for comparison: A classic hollow brick with about twice the height costs 0.72 € ($0.75-ish) in Germany.

    If anything, this is expensive (to little surprise).

    However, a) this is an impressive student project and b) I can see how a small set of insertable elements could be used to make custom shaped bricks on-site, e.g. for custom windowshapes and conduits and whatnot.

  10. If you search YouTube, there are quite a few videos of waste plastic being mixed with sand and formed into building materials. One of the most common are shingles, another are sidewalk pavers. In some of the poorer countries this has become a small business, using mostly waste materials

  11. While plastics cant be reused endlessly, it is better to reuse the plastics we have in ways that allow them to continue to be reused, and, most importantly, kept out of nature. Plastics fall apart over time, and the little bits left behind cause all kinds of problems for plants and animals… It’s best not to unnecessarily downcycle reusables into static things like park benches or construction materials (bricks).

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