ETH Zurich researchers developed a printable mixture of sand, bacteria and natural gels to make architectural elements, including a facade component. After printing, daily mineralisation baths let the bacteria form calcium carbonate crystals that bind the sand together. The material hardens at room temperature over two to five days, without firing it in a kiln.
A second method uses a robotic arm to deposit sand, bacteria and mineralising substances in successive layers, demonstrated at the 2025 Venice Architecture Biennale. Neither approach is a ready replacement for structural concrete: load-bearing applications remain distant, and the sprayed material needs further mechanical testing. The reaction also produces environmentally harmful ammonium, so waste treatment must be addressed before claiming a sustainable alternative.