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. 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.
Fused Deposition Modeling (FDM)—also known as 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 extrusion and melting 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 FDM 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.
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.
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.
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 63 ℃, while ABS has a glass transition temperature of 105℃, which can cause PLA to act as a contaminant if combined with ABS. 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.
In addition to being recyclable, PLA 3D printer filaments are also biodegradable. Since PLA is made from plant-based materials derived from crops like corn, it is eventually broken down by microorganisms into carbon emissions. 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. It is therefore helpful to think of PLA as only biodegradable if it’s processed at an industrial composting facility.
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 greener 3D printing process.
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.
Ensure 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.
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.
Opt for 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.
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 prohibitive, but it can save you money down the line in material costs.
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 plastics from PLA prints, 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 following the aforementioned steps.
 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
 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
 Is PLA Filament Actually Biodegradable? [Internet] 3DNatives; July 23, 2019 [Cited February 22, 2022] Available from: https://www.3dnatives.com/en/pla-filament-230720194/#!