Assessing 3D printing processes as enablers of circular economy

Additive Manufacturing (AM), also popularly known as 3D Printing, refers to a group of manufacturing methods which are guided by a digital model and use incremental addition of material, usually in a layer-by-layer manner, for the fabrication of objects. Lately, AM is widely used in both industry and academia, exhibiting, among others, the advantages of flexibility and ability to produce on demand, with reduced cost, time and waste. This paper seeks to shed light on the contribution of 3D printing in the transition towards the objective of circular economy. Towards this end, we focus on three AM processes (Cold Spray, Direct Energy Deposition, and Powder Bed Fusion), and we review 27 distinct case studies in the laboratory as well as industrial settings, exploring their circularity based on the comprehensive 9R framework (recover, recycle, repurpose, remanufacture, refurbish, repair, reuse, reduce, rethink, refuse). Overall, the results provide a structured assessment of the degree of circularity, and identify the dominant “R” strategies employed by the specific methods of AM. They also reveal the positive impact, and the corresponding advantages, of 3D printing in the extension of product(s) life cycle, with respect to specific material and industry sectors.