A new way to 3D print living soils could unlock the carbon-capturing homes of the future

Researchers at University of Virginia (UVA) have developed a method for 3D printing living soils that could be used to build future carbon-negative buildings.

Through the layer-by-layer extrusion of a novel seed-impregnated soil “ink,” the UVA team’s approach enables the creation of self-supporting structures that facilitate the growth of plant life. With more R&D, the researchers say their blend could replace less durable traditional building materials and enable the creation of wildlife-infused architecture that absorbs CO2 via photosynthesis.

“This method hypothesizes the creation of an active ecological system that could store emitted carbon in 3D-printed soil structures,” said Ehsan Baharlou of the UVA School of Architecture. “The only electricity we need is to move the material and run a pump while printing. If we don’t need a printed part or it’s not of the right quality, we can recycle and reuse the material in the next batch of inks.

UVA’s Ehsan Baharlou 3D prints a wall structure from living soil. Photo by UVA.

The high carbon footprint of concrete

To accurately measure the carbon footprint of a material, it is necessary to calculate the total amount of CO2 emitted during its manufacture. In the case of concrete, its manufacture is based on the combustion of fossil fuels, while the cement part of its composition consists of an aggregate composed of sand and gravel, both of which come from a limited natural supply, which makes it makes it energy efficient. too.

Thus, while CO2 emissions studies found that concrete is no more harmful to the environment than plastics or metals like steel, the sheer amount of it used in construction makes its environmental impact all the greater.

In fact, in a Lisbon University Sustainability Study last year, researchers calculated that all the forests in the world were not enough to offset half of the environmental impact of global production of aggregates and cement. With this in mind, the UVA team has now developed a new ground-based alternative that can be 3D printed into large, complex structures.

Initially, when formulating their material, the researchers used a desktop system to test two different approaches, one in which the soil and seeds were printed in sequential layers, and another where they were premixed. While both work, it has been found that while plants fight the soil for water, the moisture content of their 3D printing ink would have a profound impact on the properties of the resulting constructs.

“The 3D-printed soil tends to lose water faster and retains a stronger grip on the water in it,” explained Ji Ma, the project’s other UVA assistant professor. “The reason we think this is the case is because the ground is compacted. When the soil is pressed through the nozzle, the air bubbles are expelled. As soil loses air bubbles, it holds water more tightly.

Domes 3D printed from the team's earth-based materials.  Photo via UVA.
Domes 3D printed from the team’s earth-based materials. Photo via UVA.

3D printing of plant-infused buildings

Work with proximity Blandy Experimental Farm science station, the UVA team circumvented potential problems with soil moisture content, by incorporating very specific plant seeds into their material. Concretely, the researchers opted for stonecrop, a plant capable of thriving with little water and growing directly on bare rock.

Since developing their revised ink, the team has started 3D printing it in larger objects such as low walls around a meter high, with plants that start growing within days, and they are looking now to evolve their approach.

Use of funding granted under UVAs 3Horsemen grant program, Ma and Baharlou believe they have developed a 3D printing facility that can do just that. By mounting an extruder on a robotic arm with a reach of 3 to 4 feet, the pair discovered that it was possible to begin laying down custom materials to produce structures with a desired space, function or geometry.

While researchers predict that building taller structures will make problems like soil cracking worse, they continue to experiment with different mixes of plants and materials, including plants like hemp. However, the team says that ultimately the technology needed to 3D print robust structures does exist, hence their ongoing work is focused on identifying a material that makes the most of its benefits. unique.

“Regardless of the material – plastic, metal, clay, soil or vegetation – ultimately it’s a matter of materials,” Ma concluded. materials you work with. 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 enjoy it. This is the long-term objective of our research.

Burlasite 3D printed and infused with Simulaa mushrooms.  Photo via Simulaa.
Burlasite 3D printed and infused with Simulaa mushrooms. Photo via Simulaa.

Understandably, given concrete’s role in the ongoing impact of global warming, a tremendous amount of research is being conducted to find more environmentally friendly 3D printable building materials. Texas A&M University’s ‘hempcrete’ material, a raw material made from the hemp plant and a lime-based binder, recently gained support via $39 million in funding ARPA-E subsidy targeted towards R&D on biomaterials.

Australian Architecture Agency Simulaameanwhile 3D printed a building out of mushrooms for his entrance to last year Tallinn Architecture Biennale. The exhibit was designed to grow and encompass its wooden base, before breaking down in an algorithmic process leaving behind a tree-like ‘stump’, in a process that signified the passage of time.

The researchers’ findings are detailed in their paper titled “3D printing of ecologically active soil structureswhich was co-authored by S. Barnes, L. Kirssin, E. Needham, E. Baharlou, DE Carrc and J. Ma.

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Featured image shows UVA’s Ehsan Baharlou 3D printing a wall structure from living soil. Photo via UVA.