Sustainable 3D printing: A look at biodegradable and recycled filaments

In 3D printing, material choice directly affects waste output and energy consumption. While many manufacturers and hobbyists have begun reusing scrap as infills or printing low-fidelity wireframes to minimize their carbon footprint, these solutions do not address the root problem. Biodegradable and recyclable materials are the only feasible long-term solutions.

Seeking sustainability in 3D printing 

Researchers from the Massachusetts Institute of Technology (MIT), the National Institute of Standards (NIST) and Technology and the National Center for Scientific Research have developed a 3D printer that automatically identifies the parameters of unknown materials without human intervention. It utilizes a complex mathematical function to automatically compute workable printing parameters and adjust its settings accordingly.

It is worth noting that a typical fused filament fabrication (FFF) printer’s slicer can only accurately adjust temperature, speed and flow for reliably uniform materials. While this breakthrough could significantly accelerate the time to completion in additive manufacturing, it limits facilities’ material options, which poses an issue. 

Unlike synthetic polymers, environmentally friendly alternatives contain variable ingredients and have irregular physical properties. The specifics of biodegradable and recyclable polymers fluctuate depending on their source material and the season, preventing them from being used in an FFF printer that automatically detects printing parameters. 

While utilizing biodegradable or recyclable filament may not currently be manufacturers’ top priority, it may soon have to be with sustainability awareness and plastic bans on the rise. The Canadian government has announced its plans to be plastic-free by 2030, starting with placing a nationwide ban on single-use plastics in 2022. Other countries — and some U.S. states — have enacted similar legislation, highlighting this situation’s urgency. 

Crucially, many existing filaments that are supposedly eco-friendly are far from it. They may be made partly from organic matter, but that does not necessarily make them biodegradable. Further, many will only decompose naturally in highly controlled environments or industrial composting facilities. Regulators and legislators will notice these issues.

Exploring biodegradable filaments for 3D printing 

Polyhydroxyalkanoate (PHA) is one existing biodegradable and compostable material for 3D printing. Unlike some bioplastics, it can degrade through depolymerization within three to nine months in general. It is synthesized naturally by microorganisms through a biological fermentation process. This bioplastic filament is steadily becoming more commercially and industrially available because of its good printability, thermal stability and low melting point. 

Many research groups seek to improve upon existing materials. One turned to algae-based PHA because it has similar mechanical properties to those of fossil-fuel-derived substances. Plus, unlike other feedstocks derived from agricultural residue or food waste, it does not require large swaths of fertile land for cultivation. This filament can degrade naturally in soil, marine environments or industrial composting facilities. 

Raw hemp and polylactic acid (PLA) is a similar substance. Hemp has a high cellulose content and is easily sourced, which makes it ideal for additive manufacturing. Once manufacturers grind the stalks — and wash the shives to eliminate any impurities — they use a bonding agent between the fibers and polyesters to produce a filament.

Since PLA is derived from corn, sugars and microorganisms, combining it with hemp makes it one of the most eco-friendly options. Notably, sustainability is not this composite material’s only strength — its printability is also impressive. It can print at a lower temperature than pure PL. Also, it demonstrates better mechanical properties than many other conventional commercial-grade polymers. 

A look into recyclable filaments for 3D printing

Recyclable 3D printing materials may not be as sustainable as their biodegradable counterparts, but they remain a crucial consideration for Additive Manufacturing applications. Since they are generally more water-resistant and long-lasting, they have more commercial, industrial and biomedical use cases. 

Polyethylene-terephthalate-glycol (PETG) mixed with microalgae is among the most promising options. Combining this thermoplastic polyester with powdered chlorella vulgaris and spirulina platensis makes for a material with good printability and adequate moisture sensitivity. Filaments could be extruded to a maximum filler content of 30% — higher concentrations result in reduced throughput and unstable extrusion results. 

Emerging biodegradable  materials 

Although most manufacturers likely won’t invest in novel 3D printing materials based on peer-reviewed studies, they should, at the very least, consider them. With the rate at which this field is advancing, looking to the future to better anticipate upcoming innovations is a sound business strategy.

One of the more promising emerging biodegradable materials is a cellulose-based aerogel to be used as a 3D printing ink. Aligning cellulose fibers of different lengths at the nanoscale doubles the print’s tensile strength and helps it withstand deformation. Nanofiber alignment enhances its mechanical properties despite its low density. Intriguingly, this filament exhibits robust antibacterial activity, making it ideal for biomedical applications.

Another emerging filament involves spent coffee grounds (SCG), carboxymethyl cellulose — a water-soluble polymer derived from cellulose — xanthan gum and water. This substance degrades rapidly in soil or marine environments but is not water-soluble and can withstand cycles of drying and rehydration. 

Since only a portion of coffee’s mass is extracted during brewing, the rest is usable. Mitigating dissolution is possible using a natural, compostable beeswax coating. In other words, even hobbyists can make and print SCG filament. However, this composite possesses only approximately 1.4% of PLA’s tensile strength, meaning its commercial and industrial applications are somewhat limited.

As novel biodegradable and recycled materials continue emerging, additive manufacturers must consider how they will select their materials and printers to optimize output and sustainability. While a machine like the one from MIT and NIST could fill in the gaps, they still must consider factors like thermal resistance, antibacterial activity and biodegradability.

Author: Ellie Gabel – Featured image: Credit: Jakub Żerdzicki – Free via unsplash | Remember, you can post free-of-charge job opportunities in the AM Industry on 3D ADEPT Media or look for a job via our job board. Make sure to follow us on our social networks and subscribe to our weekly newsletter: Facebook, Twitter, LinkedIn & Instagram! If you want to be featured in the next issue of our digital magazine or if you hear a story that needs to be heard, make sure to send it to contact@3dadept.com.