Bacteria bind sand into building-grade material without cement

Researchers at ETH Zurich led by Karen Antorveza Paez used the bacterium Sporosarcina pasteurii to bind sand grains with calcium carbonate. The method works two ways: 3D-printing a bio-ink that cures in a bath for three days, and robotic spraying; the process takes up to five days without heat.

• Sporosarcina pasteurii binds sand grains via calcium carbonate
• 3D printing: sand-bacteria gel hardens in a bath for 3 days, then dries 2 days
• Robotic spraying ran unsupervised for six months
• Strength matches mortar, not concrete; ammonium by-product is toxic