A research team out of the University of Virginia (UVA) has developed a new innovative and sustainable approach to building that utilizes the power of 3D printing to create structures made of soil implanted with seeds. 

The team consists of Ji Ma, an assistant professor of materials science and engineering at UVA’s School of Engineering and Applied Science; David Carr, a research professor in the university’s Department of Environmental Sciences; Ehsan Baharlou, an assistant professor in the UVA School of Architecture; and recent UVA graduate Spencer Barnes, who earned his Bachelor of Science in aerospace engineering. Given the environmental benefits of integrating green spaces with buildings, the researchers wanted to investigate the possibility of developing complex structures made of natural materials themselves. 

Their approach combines the speed, cost efficiency, and low energy demands of 3D printing with locally-sourced, bio-based materials. This method breaks away from the typical linear approach to design and construction, where raw materials are thrown away as waste at the end of their lives, into a circular one, in which construction materials can be recycled, resulting in reduced carbon emissions. 

“We moved to soil-based ‘inks’ to derive additional benefits from circular additive manufacturing,” Baharlou said to UVA Today. “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 reuse the material in the next batch of inks.”

Barnes was tasked with conducting experiments with soil-based inks. He used a desk-sized 3D printer to explore two approaches: printing soil and seed in sequential layers and mixing seed and soil before printing. Both approaches worked, and he produced a cylindrical prototype that resembled a Chia Pet. Baharlou then proposed 3D printing more complex structures, such as domes. 

Leah Kirssin, a UVA architecture graduate, and Lizzie Needham, a Master of Landscape Architecture graduate, who assisted on the project, tested how material comes out of the printer head without any additives to the soil mixture. They found that 3D-printed soil structures can support plant growth but are limited to plants that can survive with little water. They believe the reason behind this is due to how compact the soil gets when 3D printed, which makes the environment around the plant drier. 

To identify possible plant options, Ma sought out Carr, who works as the director of Blandy Experimental Farm, an environmental science field station in Virginia’s Clarke County. He suggested plants that are naturally found in harsh settings, specifically the stonecrop, a succulent that thrives in dry, sunny locations and is commonly used in green roof settings. 

The results of the study, “3D printing of Ecologically Active Soil Structures,” were published in the journal Additive Manufacturing earlier this year.