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Steel tubular frames are often used to build a variety of structures because of their optimal mechanical properties and attractive forms. However, their joint fabrication involves a vast quantity of cutting and welding works, which induces high labour costs, material waste, and environmental pollution. The construction industry dominates the global carbon footprint, and it needs more sustainable products. Nature’s structures are also often tubular, and their joints (e.g. the knees of a human body, the nodes of trees and plants) are intrinsically optimized to maximize stiffness, resistance, and robustness. The 3D metal printing technology can enable a nature-inspired optimization of steel tubular joints, saving material waste and decreasing fabrication costs as well as the carbon footprint of the sector, since it is free from the constraints of traditional manufacturing. In this study, we designed new tubular joint shapes using solid isotropic material with the penalization (SIMP) method. The objective of the optimization was to maximize the structural performance of the node. The optimized node that used to be achieved after a complex manufacturing process composed of numerous cutting and welding operations, can now be 3D printed and then connected to the rest of the joint leading to a shorter fabrication time. We quantified the joints’ structural performance with different grades of optimization using non-linear finite element analysis. Compared with the conventional joint shapes, the new geometries offered a higher stiffness, resistance, and robustness. We performed a powder bed fusion simulation to analyze the residual stresses after production, and estimated the cost of the new solutions.

This research explores the carbon removal of a novel bio-insulation composite, here called MycoBamboo, based on the combination of bamboo particles and mycelium as binder. First, an attributional life cycle assessment (LCA) was performed to define the carbon footprint of a European bamboo plantation and a bio-insulation composite, as well as its ability to remove CO2 along its lifecycle at a laboratory scale. Secondly, the Global Worming Potential (GWP) was estimated through a dynamic LCA with selected end-of-life and technical replacement scenarios. Finally, a building wall application was analyzed to measure the carbon saving potential of the MycoBamboo when compared with alternative insulation materials applied as an exterior thermal insulation composite system. The results demonstrate that despite the negative GWP values of the biogenic CO2, the final Net-GWP was positive. The technical replacement scenarios had an influence on the final Net-GWP values, and a longer storage period is preferred to more frequent insulation substitution. The type of energy source and the deactivation phase play important roles in the mitigation of climate change. Therefore, to make the MycoBamboo competitive as an insulation system at the industrial scale, it is fundamental to identify alternative low-energy deactivation modes and shift all energy-intensity activities during the production phase to renewable energy.