Envious of your pet hermit crabs' 3D-printed domicile? Maybe you should cast your green eyes upon the Stone Spray project, an Eco-friendly robot printer that's exploring the viability of soil as a building material. Although making actual buildings is a bit out of the robot's reach, its team has managed to print a series of scaled sculptures (such as stools, pillars and load-bearing arc structures) out of sand, soil and a special solidification compound. The machine's jet-spray nozzle seems to have an easier time constructing objects over per-existing scaffolding, but the team is striving to design structures that don't require the extra support. "We want to push further the boundaries of digital manufacturing and explore the possibilities of an on-site fabrication machine," the team writes on the project's homepage, citing makeshift printed bridges or an on-beach canopy as possible applications of technology. If the Earth itself doesn't make a green enough building material, consider this: the Stone Spray robot can be powered by solar energy alone. Check it out in all of its sand-sculpting glory in the video below.