3D printing, or additive manufacturing, is often touted for its environmental sustainability. There seems to be quite a bit of substance to this too, as a 2014 study from the University of Groningen, Netherlands, found that 3D printing could reduce the overall CO2 emission intensities of industrial manufacturing by up to 5% by 2025.
The question of whether or not this is wholly true is not so simple. Several factors contribute to the carbon neutrality of a process besides just the energy usage of the manufacturing operation itself - namely, transportation emissions and material usage emissions.
In-process energy usage
To truly evaluate the carbon neutrality of 3D printing processes, it’s best to look at some real figures. Back in 2020, the Additive Manufacturer Green Trade Association (AMGTA) commissioned its first university research paper taking a deeper dive into the environmental effects of metal 3D printing (specifically, powder bed fusion). The paper concluded that, when considering direct manufacturing processes exclusively, 3D printing actually has a higher carbon footprint, per kg of material processed, than conventional manufacturing methods.
It’s worth noting at this point that there are some caveats to this rather extreme conclusion, and it is indeed looking at an average. Part geometry was found to have a major effect on the final outcome, in that it is more environmentally sustainable to subtractively manufacture a solid cube, whereas it would be best to 3D print a more complex geometry such as a lattice or hollow shell.
Production volume was also found to be a major contributor here, with conventional processes being more suited to high throughput production and 3D printing being more suited to low-volume, highly-custom manufacturing. So, the carbon neutrality of 3D printing processes themselves is not black and white and must be evaluated in the context of the parts being manufactured.
The environmental costs of material usage
It is not enough to just look at the energy usage of a laser, or the temperature requirements of polymer extrusion either. The environmental sustainability of raw material production (and subsequent recyclability) must also be considered.
Its common knowledge at this point that 3D printing is more material-efficient than conventional manufacturing. This is an undeniable truth, as the material is only deposited where it is needed and waste is minimized. On the other hand, when looking at a process like milling, manufacturers are faced with tonnes of the swath that must be disposed of every year.
So, on the surface, it looks like this is one of the areas where additive manufacturing shines - and it does, but it’s not perfect. Chemical manufacturer BASF recently conducted a life cycle analysis study that found that about half of the powder used in selective laser sintering (SLS) actually becomes waste. Of course, recycling used powder is a common practice, but this often results in performance issues that make 3D printed parts unsuitable for high-stress engineering applications.
The main problem is regarding the surface texture of 3D printed parts, and it is known as the ‘orange peel’ effect. The often rapid cooling of the powder once it leaves the build chamber causes shrinkage, resulting in residual stresses and internal defects forming within 3D printed parts. The primary solution to mitigate the orange peel effect is to just mix in fresh powder, so you can see how this isn’t a very ideal approach. Again, 3D printing in this regard can be considered environmentally sustainable in a relative sense, but its carbon neutrality is dubious at best.
Logistics and distributed manufacturing
The final factor affecting carbon neutrality is logistics and the emissions associated with part transportation. It's safe to see this is another area where 3D printing shows its strength, as it lends itself quite well to distribute manufacturing.
Companies like Ivaldi Group have built their entire business models around the concept of distributed manufacturing, and the slogan ‘Send Files, Not Parts’ described it best. With the digital-heavy focus of 3D printing, it is possible to eliminate part transportation altogether, as parts can be sent overseas as STL files to be printed locally. Of course, this has insurmountable benefits for carbon emissions, as entire cargo ships can be replaced by cloud servers.
Ultimately, we come back to the question of 3D printing’s carbon neutrality, and the answer is not as clear cut as we would like. This is entirely dependent on the case being studied, as part geometry, production volume, and the 3D printing process itself can have major impacts. Regardless, material recyclability and a lack of part transportation are indeed key benefits of the technology, so the future of additive manufacturing does look green, even if it isn't the brightest shade of green we could hope for.