CU Boulder researchers find seaweed derivative makes earthen materials viable for 3D printing

Researchers at the University of Colorado Boulder have identified sodium alginate — a seaweed-derived compound used in food manufacturing — as an additive that makes natural earthen materials like clay and sand suitable for extrusion-based 3D printing.

The research was motivated by observing how organisms such as termites, wasps, and honeycomb worms construct durable structures from soil and clay without cement, relying instead on biopolymers — large biological molecules that bind particles together.

“From termite mounds to adobe buildings, humans and animals have been building with earth since the dawn of time,” said Wil Srubar, Professor in the Department of Civil, Environmental and Architectural Engineering at CU Boulder. “But there hasn’t been a lot of science to how earthen builders design the materials. So, we wanted to use scientific knowledge and tools to understand it.”

The team tested five biopolymers — including guar gum, locust bean gum, cassia gum, xanthan gum, and sodium alginate — against natural earth excavated from a granite quarry near Golden, Colorado. Locust bean gum bound soil particles tightly but reduced printability. Sodium alginate, by contrast, altered the electrical charges on clay particles, causing them to repel one another and remain suspended in a stable, flowable mixture.

Adding just 0.12% sodium alginate by volume produced a material capable of withstanding 25% more compressive pressure than untreated earth, while printing 33% faster. The team used the formulation to print an 8-millimeter-thick wall that remained structurally stable when tilted to 60 degrees — steeper than the Leaning Tower of Pisa.

Beyond mechanical performance, the material carries potential environmental benefits for the construction sector. “There are some good indoor environmental benefits of having earth in a building,” said Samuel Armistead, a Research Associate in the Department of Civil, Environmental and Architectural Engineering. “It can regulate indoor moisture and uptake air pollutants. It can also serve as a thermal insulator, keeping things cool in the summer and warm in the winter.”

Armistead also noted the implications for construction waste diversion. “Our study suggests that there are ways to reuse waste earth material onsite, and that could largely reduce the environmental footprint of construction,” he said.

Srubar added that the material’s constituent ingredients are among the most accessible on the planet. “Clay and sand are among the most abundant building materials on Earth,” he said. “The science and engineering we’re developing can be applied almost anywhere in the world.”

The study was conducted in collaboration with scientists at Columbia University in New York, and was published in Nature Communications.