Bacteria as masons: ETH prints facade elements from sand and biocement
Instead of firing rock at over 1,000 degrees, an ETH architect gets bacteria to bond grains of sand. 3D printing and a robot turn this into building elements – without any heat.
Photo: Jawahar Swaminathan and MSD staff at the European Bioinformatics Institute / Wikimedia Commons, Public domain (cropped and resized)
Video: YouTube · ETH Zürich · youtube.com
Cement production is one of the construction industry's largest sources of CO2. At ETH Zurich, architect Karen Antorveza Paez explored an alternative in her doctoral work at the Department of Architecture: bacteria of the species Sporosarcina pasteurii bond grains of sand into solid building elements. Microscopic, interlocking calcite crystals form between the grains – a process known as biocementation. ETH presented the work on 14 October; it is described in three papers, including one in npj Materials Sustainability.
For 3D printing, the team developed a bio-ink made of a gel containing alginate and xanthan, sand and live bacteria. The printed object is placed in a bath of urea and calcium chloride. The bacteria break down the urea with the enzyme urease, which produces limestone. Depending on the desired strength, this takes two to five days, and no heat is needed. One result is a facade element that can serve as sun protection or a partition wall. A second method uses a robotic arm to apply bacteria, minerals and sand layer by layer; at the 2025 Architecture Biennale in Venice it ran for six months without interruption.
Load-bearing components are still a long way off: according to Antorveza Paez, biocement is currently more like mortar than concrete. Ammonium is also produced as an environmentally harmful by-product, and its disposal has to be factored in. She is currently working on a further study on this.