A hybrid structure made of willow and earth

With their project ReGrow Willow, a team of Karlsruhe Institute of Technology (KIT) demonstrates the possibilities of digital circular construction with natural materials.

The project consists of an earth-willow hybrid structure for architectural and construction applications, and offers an alternative to the finite resources the construction industry usually depends on. Willow is a rapidly renewable biobased material that can be composted at end-of-life, while earth is infinitely recyclable without loss of value.

In the project, the willow serves as tension reinforcement for the earth. This is advanced through tailored computational workflows. The tricky part is that each piece of willow, being a natural material, varies from the next. Therefore, the project emphasizes the co-evolution of the material system and the fabrication process.

To do this, a comprehensive fabrication system was developed, starting with a two-axis machine capable of extruding and depositing continuous macro-fibres made from spliced willow branches. Controlling the machine’s extrusion, movement, and deposition path proved challenging due to factors such as the flexibility and varying thickness of willow branches, as well as the requirement for tensioning in the final components.

The earth is shot into selected sells within the willow formwork using a modified plastering machine. The geometry of the willow formwork allows for seamless integration with the earth, without the need for any additives or adhesives.

Photos: Karlsruhe Institute of Technology