New Artificial Coral REefs by 3D printing of biosourced materials for the reconstitution of the marine ecosystem – NACRE-3D

Coral reefs play a key role in the marine environment, its balance and biodiversity, providing hatching grounds and shelter for a wide range of organisms. They also help protect coastlines from erosion. However, their decline is now a proven fact, accelerated by global warming and ocean acidification. Almost a quarter of these reefs have already disappeared. One strategy for restoring damaged areas is to build and deploy artificial reefs, but several obstacles remain: (i) materials used to date are not environmentally-friendly, and (ii) they are shaped according to architectures that do not match to the original. NACRE-3D aims to overcome these obstacles through the development of biomimetic artificial coral reefs using 3D additive manufacturing based on sustainable, partly recycled materials with a chemical composition close to that of coral. More specifically, NACRE-3D explores the potential of a low-cost 3D printing technology, Binder Jetting, whose flexibility makes it possible to manufacture both small and large structures with multi-scale porosity adapted to different restoration cases. The raw materials used are CaCO3 powders recycled from oyster shells, and the binders employed are biosourced. In addition, the 3D structures are functionalized with coral growth boosters and/or antifouling agents using porous CaCO3 microspheres, synthesised on demand, which can be loaded with active species and used as delivery vectors. Biomimetic, durable and functionalized 3D structures are tested on site, in representative marine environments, and their efficacy compared to current restoration solutions.