PLA Recycling: Can PLA 3D Printer Filament be Recycled?

Plastic waste is a global problem that we face today. Every year, millions of tons of plastic waste end up in the ocean, which wreaks havoc on aquatic ecosystems and the communities that rely on them.[1] As a technology that consumes plastic materials, 3D printing plays a role in this global issue and has an environmental impact. It is therefore important that materials such as PLA, one of the most widely used 3D printing thermoplastics, can be reused and recycled.

In this article, we’ll explain how recycling works for 3D printer filaments, take a specific look at PLA as a biodegradable material, and explore ways to cut back on 3D printing plastic waste in the first place.

Can you Recycle 3D Printer Filament?

Fused Filament Fabrication (FFF) is today the most widely used 3D printing technology in the world. The process, which comes in various shapes and sizes, essentially relies on the simultaneous melting and extrusion of plastic filament materials onto a print bed. When the layer of melted plastic cools, the material solidifies. This is repeated layer by layer, until a three dimensional object is created. 

The entire FFF process is enabled by the fact that 3D printer filaments are made from thermoplastic materials. Thermoplastics are characterized by their ability to melt when exposed to relatively low temperatures and re-solidify when cooled. This material property also means that thermoplastic filaments can be recycled, as material waste can be melted down and reprocessed as pellets or new filament with minimal effects on the material quality or integrity.

3D printer filaments like PLA and ABS are classified as Type 7 plastics, not widely accepted by local recycling centers.

However, while it is technically possible to recycle 3D printer filament, the process is not quite as simple as putting leftover material waste, like supports or failed prints, into the recycling bin to be picked up by your local recycling center. In fact, PLA, ABS, and other common 3D printing filaments are grouped under “Type 7” plastics, which most municipal and community recycling centers do not process. 

So how does one go about recycling leftover 3D printing filament? There are a couple of options. First, your town or city may have a specialist recycling center that does process Type 7 materials. If this is the case, you can bring your failed prints and scrap plastic to them to be recycled. Some local maker spaces or 3D printing labs also collect scraps to be sent to a dedicated recycling plant. Alternatively, you can bring your leftover plastic filament and scraps to a material recovery facility, which sorts recyclable plastics and sells them to manufacturers. 

If you want to create your own circular economy for 3D printing materials, it is also possible to recycle 3D printer filament at home using a filament extruder. In the simplest terms, this piece of equipment is a machine that melts raw plastic pellets and extrudes the thermoplastic as a filament. If you plan to use failed prototypes and support materials as raw material, you may also need a plastic shredder to turn the parts into pellets that can be processed by the extruder system. With a filament extruder, you can transform your 3D printer waste into new filament, cutting back on waste and saving money in the long term. It should be noted, however, that recycling filament at home can lead to lower quality materials if not done correctly, which increases the risk of part warping.

Recommended reading: Comparison of PLA, ABS, and PETG Filaments for 3D Printing

Can You Recycle PLA?

Polylactic Acid (PLA) is among the most commonly used 3D printing filaments today. This is due to a number of factors, including the material’s excellent printability, good dimensional accuracy, and affordability. PLA is also popular because, as a polymer derived from plant starches, it is more eco-friendly than filaments derived from non-renewable resources (such as petroleum-based ABS) and has the benefit of being recyclable and compostable.

If recycled, PLA must be processed on its own to avoid contaminating other plastic materials.

When it comes to recycling PLA filament, the most important thing to know is that it cannot be mixed with other types of plastic and must be processed alone. This is because PLA has a lower melting point than ABS and other common filaments. For example, PLA’s glass transition temperature is around 60 ℃, while ABS has a glass transition temperature of 105℃, which can cause PLA to act as a contaminant if combined with ABS.[2] Because PLA must be processed separately from other plastics due to the lower melting temperature, many plastic recycling programs do not accept the material. As an alternative, you can choose to recycle your own PLA waste using a plastic shredder and a filament extruder.

A big selling point of PLA 3D printer filament is that it is biodegradable. Since PLA is made from plant-based materials derived from crops like corn, it is eventually broken down by microorganisms. That being said, it is not a good idea to simply toss PLA printing scraps into trash in the hopes that they will decompose quickly in a landfill. Without the right composting conditions, it can still take PLA hundreds of years to degrade. If PLA material is disposed of in the right conditions—with controlled temperature, humidity and microorganisms—it can break down in just a few months.[3] It is therefore helpful to think of PLA as only biodegradable if it’s processed at an industrial composting facility.

Recommended reading: PLA bed temperature & print temperature settings

Recycling Processes for PLA

At an industrial level, there are two primary methods for recycling PLA and other thermoplastic filaments: mechanical recycling and chemical recycling.

Mechanical recycling

Mechanical recycling is a widely used method for processing PLA waste. This process involves the physical transformation of PLA waste into new products without altering its chemical structure. The mechanical recycling process typically consists of several stages, including size reduction, washing, drying, and reprocessing.[4]

In the size reduction stage, PLA waste is shredded or ground into smaller particles, making it easier to handle and process. Washing is then performed to remove contaminants, such as dirt, food residues, and other impurities. This step is crucial for maintaining the quality of the recycled material and ensuring that the final product meets the required specifications.

After washing, the PLA particles are dried to remove any remaining moisture. This is because excess moisture can cause issues during the reprocessing stage, such as the formation of bubbles or defects in the final product. Once the PLA particles are dry, they are melted and extruded through a die to form new products, such as pellets, fibers, sheets, or filaments. These recycled PLA products can then be used as raw materials for manufacturing new items, effectively closing the loop in the PLA life cycle.

Scrap PLA materials can be reprocessed and recycled into new 3D printing filament.

Mechanical recycling offers several advantages, including lower energy consumption and reduced greenhouse gas emissions compared to the production of virgin PLA. However, it also has some limitations. Repeated mechanical recycling can lead to the degradation of PLA's physical properties, such as strength and transparency, due to the exposure to heat and mechanical stress during the process. This degradation can limit the number of times PLA can be mechanically recycled and may require the addition of virgin material or additives to maintain the desired properties of the recycled product.

Chemical recycling

Chemical recycling is an alternative method for processing PLA waste that involves breaking down the polymer into its constituent monomers or other valuable chemicals. This process allows for the recovery of high-quality materials that can be used to produce new PLA or other products, overcoming some of the limitations associated with mechanical recycling.[5]

There are several chemical recycling techniques for PLA, including hydrolysis, methanolysis, and glycolysis. Hydrolysis involves the use of water and an acid or base catalyst to break the ester bonds in the PLA polymer chain, resulting in the formation of lactic acid. Lactic acid can then be purified and polymerized to produce new PLA or used as a building block for other chemicals and materials.

Methanolysis and glycolysis are similar processes that use methanol or ethylene glycol, respectively, as the reaction medium. These methods result in the formation of methyl lactate or glycolide, which can be further processed to recover lactic acid or other valuable chemicals. The choice of chemical recycling method depends on factors such as the desired end products, the available processing equipment, and the specific properties of the PLA waste.

Chemical recycling offers several advantages over mechanical recycling, including the ability to recover high-quality materials with minimal degradation of properties. This process can also handle PLA waste with higher levels of contamination, as the purification steps can remove impurities more effectively than washing in mechanical recycling. However, chemical recycling typically requires more energy and generates more greenhouse gas emissions than mechanical recycling due to the use of chemicals and the need for high-temperature processing.

Despite its challenges, chemical recycling has the potential to play a significant role in the sustainable management of PLA waste. By recovering valuable materials and reducing the need for virgin resources, chemical recycling can contribute to a more circular economy for PLA and other plastics.

DIY PLA filament recycling

Do-it-yourself (DIY) PLA recycling is an approach that enables individuals to process and reuse PLA waste at home or in small-scale settings. To recycle PLA at home, specialized equipment is required, including a shredder or grinder, a filament extruder, and a spooler. The shredder or grinder is used to reduce the size of the PLA waste into small particles, making it easier to process. It is essential to ensure that the PLA waste is clean and free of contaminants before shredding to maintain the quality of the recycled material.

Once the PLA waste has been shredded, it can be fed into a filament extruder, which melts the material and extrudes it through a nozzle to form a continuous filament. The diameter of the filament can be controlled by adjusting the extrusion speed and nozzle size. A spooler is then used to wind the filament onto a spool, making it ready for use in 3D printing.

While DIY PLA recycling offers several benefits, such as reducing waste and promoting a circular economy, it also has some drawbacks. The initial investment in equipment can be relatively high, and the process requires a certain level of technical knowledge and skill to achieve consistent results. Additionally, the quality of the recycled filament may not be as high as commercially available products, which can affect the performance of the final printed objects. Despite these challenges, DIY PLA recycling can be a viable option for individuals and small businesses looking to minimize their environmental impact and reduce material costs.

How to Reduce Plastic Waste

Minimizing the amount of supports can help cut back on plastic waste.

In addition to recycling 3D printing waste, there are many steps you can take to actually reduce the amount of waste your 3D prints generate, resulting in an overall more sustainable 3D printing process (as well as reduced spending on materials).

Minimize support materials

Support materials play an important role in the FDM 3D printing process, ensuring that parts are stabilized on the print bed. But they are also a significant source of plastic waste. You can minimize the amount of supports by integrating them directly into the 3D model using smart design or by orienting your part strategically on the build platform. Some slicing software programs will also let you manually adjust the amount of supports.

Proper bed adhesion

If the first layers of your print job are not sticking to the print bed, there is a strong chance your final print will be defective. Minimize the risk of failed prints (and thus wasted material) by encouraging proper first layer adhesion. For example, using an adhesive or integrating a brim into your design can help adhesion without much added waste material. If you do notice your first layers aren’t sticking, stop the print as early as possible to avoid additional wasted material.

Recommended reading: What to do when PLA is not sticking to print bed

Regular 3D printer maintenance

Another good way to reduce the risk of failed prints and material waste is to ensure regular 3D printer maintenance. Making sure that your printer’s hardware is up to standard and that settings and calibration are correct can increase the machine’s output and reliability, thus resulting in a better success rate for print jobs.

Using recycled filaments

To reduce your environmental impact even further, you can choose to purchase filament from brands that use recycled thermoplastics as raw material. Some companies even provide filament spools made from recycled material or fully recyclable material. This is a more sustainable option as you are participating in a longer life cycle for the plastic material.

Invest in a filament extruder

To establish your own circular 3D printing economy, it might be worthwhile to invest in a filament extruder. This will allow you to recycle any plastic 3D printing waste you generate and turn it into more filament. The upfront cost of the hardware may be high, but it can save you money down the line in material costs and will promote greater sustainability.

Conclusion

As a 3D printer user, it is important to recognize that the technology has an environmental impact as it both consumes plastic and generates waste. Fortunately, there are ways to make the process more sustainable. Even though many local recycling facilities aren’t equipped to process PLA plastics, you can make the effort to seek out specialized facilities that do, find industrial compost centers that accept bioplastics, or recycle your own filament at home. You can also reduce the amount of waste created in the first place by doing things like minimizing support materials, ensuring proper bed adhesion, maintaining your 3D printer, and more.

Frequently Asked Questions (FAQs)

Q: What is PLA?

A: PLA, or polylactic acid, is a bio-based plastic derived from renewable resources such as corn starch, tapioca roots, or sugarcane. It is widely used in industries like packaging, textiles, and 3D printing due to its favorable properties, including biodegradability.

Q: How is PLA recycled?

A: PLA can be recycled through mechanical or chemical processes. Mechanical recycling involves shredding, washing, and reprocessing PLA waste into new products, while chemical recycling breaks down PLA into its constituent monomers or other valuable chemicals. Both processes extend the material’s life cycle.

Q: Is PLA biodegradable?

A: Yes, technically PLA is a biodegradable material since it is made from plant-based resources, like sugarcane and corn. However, PLA plastic can still take hundreds of years to fully decompose if it is not disposed of properly. PLA requires special composting conditions, with controlled temperature and humidity, as well as special microorganisms, which accelerate the decomposition process.

Q: Can PLA be recycled at home?

A: Yes, PLA filament can be recycled at home using specialized equipment, such as a shredder, filament extruder, and spooler. It is, however, important to note that the quality of the recycled filament can start to degrade over time as it is recycled over and over again.

Q: What are the environmental benefits of PLA recycling?

A: PLA recycling helps reduce waste, decrease the consumption of virgin resources, and lower greenhouse gas emissions compared to the production of new PLA. By recycling PLA, we can promote a more sustainable and circular economy for biodegradable plastics.

References

[1] The world's plastic pollution crisis explained. [Internet] National Geographic; June 19, 2019 [Cited February 22, 2022] Available from:  https://www.nationalgeographic.com/environment/article/plastic-pollution 

[2] PLA vs. ABS: Which Filament Should One Use? [Internet] Wevolver; April 23, 2021 [Cited February 23, 2022] Available from: https://www.wevolver.com/article/pla-vs-abs-which-filament-should-one-use 

[3] Is PLA Filament Actually Biodegradable? [Internet] 3DNatives; July 23, 2019 [Cited February 22, 2022] Available from: https://www.3dnatives.com/en/pla-filament-230720194/#! 

[4] Mechanical recycling [Internet] Plastics Europe; 2023 [Cited October 26, 2023] Available from: https://plasticseurope.org/sustainability/circularity/recycling/mechanical-recycling/ 

[5] McKeown P, Jones MD. The chemical recycling of PLA: A review. Sustain. Chem. 2020 Jun;1(1):1-22. Available from: https://doi.org/10.3390/suschem1010001