University of Virginia researchers have invented a method of 3D printing with seed-impregnated soil, which could be used to create walls and roofs teeming with plant life. Prototypes built by the researchers start off looking like ordinary raw-earth structures. But over the course of a few days, they sprout and become covered in greenery, leading the University of Virginia (UVA) to compare them to "oversized Chia Pets". Building elements such as green walls and roofs could be constructed using this method, bringing benefits like natural insulation, flood prevention and green spaces for people, pollinators and other animals, according to UVA.

Buildings made with this technique have the potential to be carbon neutral or even carbon negative, as their plant covering would draw down carbon dioxide from the atmosphere.

By combining soil and seeds into 3D-printable "soil inks", greenery could be built into the very fabric of architectural features rather than just layered on top. This has the potential to reduce the need for more emissions-intensive building materials and replace them with a circular alternative, which the researchers say can be can be reused again and again. "We are working with local soils and plants mixed with water," said Ehsan Baharlou, an assistant professor at UVA's School of Architecture. "The only electricity we need is to move the material and run a pump during printing." "If we don't need a printed piece or if it isn't the right quality, we can recycle and reuse the material in the next batch of inks."