Body parts cast from recycled polystyrene resin, 2023.

The first round of styrofoam donations. Please note that the glossy style of PS in the top right does not react to D-Limonene.

EPS dissolving in D-Limonene solution

The limonene/PS solution after two weeks of evaporation under ventilation.

Dried ingots of the limonene/PS solution ready to be cured.

Dried PS ingots in silicone ear molds

Recycling Polystyrene into Castable Resin

In late 2022, I found a protocol online by Adric Menning (click here) for recycling polystyrene into useable, castable resin at home using D-Limonene, an essential oil extracted from orange peels. The author describes the solvent as “nontoxic, biodegradable, renewable, and pleasantly citrus-scented,” and the process they outlined looked straightforward and safe enough. 

In Tio'tia:ke/Mooniyang/ Montreal, currently only two EcoCentres accept styrofoam. There, they’re broken down into semi-translucent resin which can then be cast into different objects or thrown into a landfill at a lower volume. For most people, it’s not accessible to make a special trip to LaSalle or Saint-Laurent to recycle their styrofoam, so it gets thrown in the garbage.

In spring 2023, I partnered with the Centre for Creative Reuse, 4th Space and the Speculative Life BioLab at the Milieux Institute to try to replicate this industrial recycling process as part of an artist residency. My initial goal for this residency was to use Concordia as a test case to show that safe and effective household styrofoam recycling can done at the level of individuals, neighbourhoods, and communities. After putting a call-out for donations from the public, we collected a huge volume of styrofoam in 4th space to process into resin under the BioLab’s fume hood. Between the BioLab and my backyard, I made the resin and casted it into ear shapes that I’d molded from my own head. 

Originally I wanted to replicate the original experiment using only free or cheap and accessible home resources to show that it could be done as part of a larger scale, DIY process.  In the end this was not possible for safety reasons, but with the BioLab’s help we were able to improve upon the original procedure for further experiments under lab conditions, and to suggest safer procedures for small-scale home experiments.

My investment in this project is that I’m fed up with the ecofascist argument that disability justice and environmental justice at odds. I’m interested in doing research creation that could intervene here, to support my lived experience that disability and environmental justices aren’t just compatible, but one and the same. 

To this end, I wanted to do something with the big, gross, Styrofoam cooler boxes I receive on a monthly basis for shipments of life-sustaining medication. The EcoCentre route isn’t accessible for me, so over time the boxes had started to pile up. I held on to them, unwilling to throw them out and hoping that someday I’d find a plausible (ideally creative) re-use for them, without producing more landfill waste. The resultant resin ears are being made into earrings to give to friends, and also make for pleasingly uncanny paperweights. 

Risk Assessment 

D-Limonene is flammable at its liquid and vapour states, fatal if swallowed, an aspiration hazard and skin irritant, and is very toxic to aquatic life with long lasting effects. Nitrile gloves, safety glasses and a closed lab coat have to be worn at all times while handling, and handling must be done in a well-ventilated area. Unused or spilled D-Limonene is not soluble in water and cannot be poured down the sink or rinsed. Solvent container and anything in contact with the solvent has to undergo a two week drying period under ventilation, then cleaned with an isopropyl-based disinfectant to be safe to put in regular garbage (not recycling). Liquid D-Limonene needs to be disposed of as hazardous waste through an Eco-Centre. 

The D-Limonene/ polystyrene solution is very hazardous. Limit contact as much as possible.  It can cause skin and serious eye irritation, harmful if inhaled, may cause fertility issues and is a teratogen. Therefore, the solution of D-Limonene and polystyrene should be considered as more dangerous for the researcher than the limonene itself. Exercise extreme caution and limit contact as much as possible. Gas emitted when the dried mixture is heated could be acrid and potentially hazardous. 

Tools and Materials: 

Lab experiment only:

over 100g of polystyrene of any kind (including expanded polystyrene) except packing peanuts-style 

A fume hood

Home experiment only:

An open, outdoor space that won’t be disturbed for two weeks

up to 100 g of unexpanded polystyrene from food packaging for home experiments 

Both lab and home experiments:

Small toaster oven 

Sealable, airtight container in a non-reactive material, like glass canning-style jars 

D-Limonene (under 100ml for home experiments)

Long spatula or spoon

Large flat drying dish in a non-reactive material, like an aluminium cookie sheet

Nitrile gloves

Eye protection

Lab coat

Silicone or steel molds 

Fire extinguisher

Heatproof gloves 

Procedure

You have to have a fire extinguisher on hand for every phase of the experiment. Source polystyrene and break down manually to fit into your container.

The correct ratio of polystyrene to D-Limonene is 1 gram: 1 millilitre. Measure both out in advance. The final volume of the limonene/polystyrene mixture will be the approximately the same as the total initial volume of the limonene, so as you measure out the limonene make sure to leave at least two thirds of headroom volume in the container to prevent the gas from becoming pressurized.

Under ventilation at room temperature, add a small amount of the solvent to your sealable, airtight container.

Begin adding your polystyrene in chunks. It will start to bubble and release gas immediately.

Gradually stir in the remainder of the D-Limonene and polystyrene, alternating. You can stir it continuously until fully processed or you can close the container between additions, de-gassing occasionally. At this stage, don’t seal the container completely and never leave it unattended, as it can become an explosion hazard if the gas is allowed to become pressurized in the sealed container. Expanded polystyrene will process faster than unexpanded polystyrene. 

For lab experiments processing expanded polystyrene, the mixture will emit pentane gas, volatile organic compounds, and flame retardants.  It is currently not known if the gases emitted from unexpanded polystyrene during this phase are hazardous, so caution should be exercised. Add additional #6 PS objects at this point if you want a coloured end product. Once all bubbles have released, spoon the solution out onto a large, flat drying dish. Exercise extreme caution and limit contact with the mixture as much as possible. 

Leave for two to three weeks open under ventilation to dry/ off-gas, stirring and folding the semi-solidified mixture over after one week to expose the underside. Due to the flammability of the D-Limonene vapours, the D-Limonene/ polystyrene solution can’t be cured until the solvent has completely evaporated. Do a touch test with gloved fingers to assess if the mixture is still sticky or tacky. The mixture is ready to be processed when it has solidified to a gummy texture and is dry to the touch. The drier this mixture is before curing, the harder and glassier the end product will be. 

Wax the steel molds, if using, and clip off small pieces of the solidified mixture with scissors to fill the molds. The solution cannot come into direct contact with the heat source: overflow from the molds should be prevented by placing molds over a tray before inserting into oven. 

Under ventilation, cure the mixture at 210F for 30-45 minutes using a small toaster oven, until smooth and glassy.  When the time is up, switch the oven off and allow 30 seconds for fumes to dissipate from the oven before opening the door and retrieving the material. If the molds aren’t full enough, you can add additional globs of the mixture and cure for another 10 minutes, or until fully melted. Pop bubbles with a small pin as needed.

Allow to fully cool down to room temperature and de-mold. Allow to off-gas under ventilation overnight. Clean your tools and work area with an isopropyl-based disinfectant or ethanol. At this point, it will be hardened to soft rubber. Once cooled and solidified, it is safe to handle by hand. Cast objects will transition to a glass stage over several months.

Notes 

A procedure for home experiments that processes over 100g of polystyrene/ 100ml of D-Limonene causes unnecessary environmental air contamination. Distillation or vacuum distillation procedures instead of the two week evaporation process would allow for the recovery of D-Limonene, which also allows for its reuse. Increasing the ratio of limonene volume to polystyrene weight will result in a softer, malleable end product that may never harden. 

Further research

Adapting procedure for home/ DIY projects: 

Not recommended for experiments over 100ml of D-Limonene/100g polystyrene without a fume hood due to air contamination. A toaster oven and any other tools used for this experiment can’t then be used for food preparation and would then need to be designated only for experimental use or sent to a landfill. Bioplastics can’t be used in the place of silicone molds for this experiment because they can’t be heated to 210 degrees F without melting.  Because the D-Limonene and polystyrene/D-Limonene solution are very hazardous, this is not recommended without the right safety training and a means to dispose of hazardous waste in the event of accidental spillage. Any tools or materials that have come into contact with the wet mixture and can’t be reused (nitrile gloves, paper towels) need to be disposed of as solid hazardous waste at an Eco-Centre. 

The original author suggests that this experiment might be replicated using cosmetic-grade lavender essential oil, which may mediate some of the risks. More research is needed to establish the efficacy and safety of this alternative method. 

Credits and Acknowledgements

This research was supported by the Centre for Creative Reuse, 4th Space, and the Speculative Life BioLab at Concordia University. It would not have been possible without these people and organizations providing logistical, financial and emotional support. 

Additional information:

Please see the Safety Data Sheet for D-Limonene. 

Backyard curing station. Tio’tià:ke.