Life Cycle Assessment of Composites Additive Manufacturing Using Recycled Materials

Abstract

Additive manufacturing (AM) of composite materials is promising to create customizable products with enhanced properties, utilizing materials like carbon fibers (CFs). To increase their circularity, composite recycling has been proposed to re-introduce the recovered components in AM. A careful evaluation of recycling is necessary, considering the sustainability and functionality (i.e., mechanical properties) of the recovered components. Thus, Life Cycle Assessment (LCA) is applied to estimate the environmental impacts of AM via Fused Filament Fabrication (FFF), using virgin or recycled CFs via solvolysis at a laboratory scale. This study aims to provide a detailed Life Cycle Inventory (LCI) of FFF and evaluate the sustainability of using recycled CFs in AM. For both virgin CF manufacturing and CF recycling, electricity consumption was the main contributor to environmental impacts. CF recovery via solvolysis resulted in lower impacts across most impact categories compared to AM with virgin CFs. Different scenarios were examined to account for the mechanical properties of recycled CFs. AM with 75% recycled CFs, compared to 100% virgin CFs undergoing landfilling, resulted in over 22% reduction in climate change potential, even after a 50% loss of recycled CF functionality. Overall, this study offers insights into the LCI of FFF and shows that CF recycling from composites is worth pursuing.

Recycling as a Key Enabler for Sustainable Additive Manufacturing of Polymer Composites: A Critical Perspective on Fused Filament Fabrication

“…This is an important point because the environmental friendliness of FFF depends on the specific application and the operating loads that the printed parts must withstand [49]. Also, a cradle-to-gate analysis does not consider the end-of-life stage of a product, and this is a crucial point, as disposal may be difficult for composite parts that contain heterogeneous materials [50].…”

“…For example, encouraging results are emerging regarding the environmental sustainability of close-looped recycling of carbon fibres in FFF through solvolysis. However, this recovery process is likely to cause fibres to degrade, and the functionality loss, which largely depends on the specific recovery process, will ultimately dictate the load-bearing capacity and the lifetime of the printed object [50].…”

“…Similarly, the price of printable filaments produced with 80:20 (wt:wt) blends of recycled PET and recycled HDPE can be estimated to vary between 4 and 10 USD/kg, while virgin PETG was rated at 25 USD/kg, and virgin HDPE at almost 60 USD/kg [162]. Despite this potential economic advantage, the thermo-mechanical degradation of the polymer matrix and the recycling-induced deterioration of the reinforcement may lead to a noticeable functionality loss [50], which will finally lower the value (and hence the market price) of the produced filament. The assessment of the economic viability of recycling will thus depend on the nature of the constituent phases of the composite material, as well as on the specific procedure followed upon recycling [50].…”

“…Despite this potential economic advantage, the thermo-mechanical degradation of the polymer matrix and the recycling-induced deterioration of the reinforcement may lead to a noticeable functionality loss [50], which will finally lower the value (and hence the market price) of the produced filament. The assessment of the economic viability of recycling will thus depend on the nature of the constituent phases of the composite material, as well as on the specific procedure followed upon recycling [50]. Regardless of economic considerations, recycling may become the only viable option because of the stringent environmental legislation being enforced worldwide [135].…”

The Development of Sustainable Polyethylene Terephthalate Glycol-Based (PETG) Blends for Additive Manufacturing Processing—The Use of Multilayered Foil Waste as the Blend Component

“…The developed method may be a way of managing waste that is difficult to reuse in the production of other types of foil for this reason. Obvious issues related to the LCA analysis of FDM filament products, estimation of the level of energy consumption, and greenhouse gas emissions might be a broad topic for discussion [ 33 , 34 , 35 , 36 ], but such a complex analysis was not the main topic of this research work. A detailed analysis could obviously help in accurately assessing the impact of the addition of foil to the tested polymer materials, but, from the point of view of the end user, the more important information is the functional properties that can be obtained for the developed materials [ 32 ].…”