Researchers developed 3D-printed living soil walls that can support plant growth

They created a cylindrical prototype resembling a Chia pet.
Nergis Firtina
Ehsan Baharlou, an assistant professor in UVA’s School of Architecture.
Ehsan Baharlou, an assistant professor in UVA’s School of Architecture.

Tom Daly/University of Virginia 

We can observe how far the architecture has progressed with the developing technology today. Referring to this, we have even seen houses made with 3D printing technology before.

Now, a group of scientists from the University of Virginia is raising the bars of 3D printing technology by producing 3D-print soil structures which can grow plants on their surfaces.

Researchers have developed a method of 3D printing with seed-impregnated soil that could be used to create plant-filled walls and roofs.

It was published in Additive Manufacturing in April.

Assistant professor Ji Ma, research professor David Carr, and assistant professor Ehsan Baharlou from UVA came together to make this project happen. They have demonstrated that 3D-printing geometrically complex structures made of soil and seed is feasible, ushering in significant innovation in bio-based construction.

Researchers developed 3D-printed living soil walls that can support plant growth
Experiments conducted by Baharlou's research team revealed that 3D-printed soil structures can support plant growth.

The researchers' prototypes begin to resemble ordinary raw-earth structures. However, they sprout and become covered in greenery after a few days.

“We moved to soil-based ‘inks’ to derive additional benefits from circular additive manufacturing,” Baharlou said.

“We are working with local soils and plants mixed with water; 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 re-use the material in the next batch of inks.”

Combining dirt and seed

Spencer Barnes, one of the students who contribute to the research, experimented with soil-based inks. Using a desk-sized 3D printer, he tested two methods: printing soil and seed in successive layers and combining dirt and seed before printing. Both methods were effective. Barnes created a cylindrical prototype that resembled a Chia pet.

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Baharlou then proposed 3D-printing soil structures with more complex geometries, such as domes.

“3D-printed soil tends to lose water more quickly and keeps a stronger grip on the water it has,” Ma said. “Because 3D printing makes the environment around the plant drier, we have to incorporate plants that like drier climates. The reason we think this is the case is that the soil gets compacted. When the soil is squeezed through the nozzle, air bubbles are pushed out. When the soil loses air bubbles, it holds onto water more tightly.”

"You can try or be afraid"

After the positive results, the researchers started to print low walls of about one meter.

They will then consider attaching the 3D printing apparatus to a moving robot to produce constructions that are taller and more intricate with numerous sides.

The researchers expect that the added height will make issues like soil cracking worse in this subsequent stage, thus they will need to refine the recipe for their "soil inks."

“Regardless of the material – plastic, metal, clay, soil, or plant life – in the end, it’s a materials problem,” Ma said. “The additive manufacturing process creates uncertainties and opportunities within the material system you’re working with that’s different from conventional systems. You can approach this in different ways. You can try to avoid it and be afraid of it. Or you can try to control it and take advantage. That’s the long-term goal of our research program.”

Study abstract

This study investigates the feasibility of 3D printing soil structures that could support plant life. Stand-alone soil structures were successfully printed without additives using an extrusion method. When the water content is properly controlled, the printed structures are able to support germination and growth of plants. Additionally, we show that the water retention capabilities of printed structures differ from potted soil of the same composition. In three different soil textures, we correlate the drying characteristics with the ability of the soil to support plant growth, and show a fundamental difference in the soil-water characteristics of the extruded soils.

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