Metal additively versus conventionally manufactured structures – An environmental life cycle assessment

The use of wire arc additive manufacturing (WAAM) in conjunction with topology optimisation enables the production of structural components with significantly higher strength‐to‐weight ratios than conventional structural components. However, owing to the additional production stages involved in WAAM (e.g. arc welding), a common question arises regarding the environmental impacts of using WAAM to produce structural components relative to conventional fabrication techniques (e.g. hot‐rolling.) A cradle‐to‐gate life cycle assessment is conducted herein to compare the environmental performance of a conventional hot‐rolled I‐section steel beam with that of a topologically optimised WAAM beam, the latter having 53% lower mass than the former. With regards to climate change, it is demonstrated that, for a typical deposition rate of 2 kg/h, WAAM can lead to lower CO₂‐eq. emissions than conventional hot‐rolling if topology optimisation can offer mass reductions of at least ∼50%. The contribution of the individual processes in WAAM production is analysed, demonstrating that the use of shielding gas is the greatest contributor to the climate change impact of WAAM production.