Living Bacteria Create Stunning Sand Structures at ETH Zurich

Summary

ETH Zurich researcher Karen Antorveza Paez developed two robot-assisted methods that use Sporosarcina pasteurii bacteria to bind sand into architectural elements at room temperature. These methods, 3D biocement printing and stromatolit-inspired layer-by-layer spraying, eliminate the need for ovens.

Why it matters

Cement production requires temperatures above 1,000 °C and is a significant source of CO₂. A biological alternative that 'grows' mineral structures at room temperature could fundamentally change the production of low-rise architectural components. The work also introduces a new design variable for architects, forcing them to treat material not as a static input but as a living process: time and bacterial activity.

Highlights

• Two complementary techniques: extruded bio-solution cured in a urea/calcium bath (2–5 days) and robotic spraying, which was displayed continuously for six months at the 2025 Venice Biennale.
• The material is compared more to mortar than structural concrete. Particle size, bacterial concentration, and drying conditions still require optimization.
• A significant unresolved environmental issue: the urea hydrolysis reaction releases ammonia, a pollutant examined in the team's third research phase.

Critical take

The sustainability claim is weakened by a fact acknowledged in the article itself: the ammonia byproduct harms the environment if not properly managed. Until this waste stream is resolved, it is premature to label the method a green alternative to cement. Additionally, the demonstrated outputs are still limited to modest facade panels. As the article notes, the difference between a laboratory-scale mortar and a load-bearing, code-compliant structural material likely requires decades of refinement.