Green Architecture Could Mean Building with Plant Polymers

3D-printed nanocellulose and algae as a sustainable alternative to fossil-based materials

Image credit: Rachel Lense for The Science Writer

by Alyssa Traitz
December 8, 2024

In the quest for a greener construction industry, researchers are tapping into tiny building blocks of plants called nanocellulose to create a more sustainable economy.

The construction sector accounted for about 37% of global energy and process-related carbon emissions in 2022 — an all-time high, according to the UN Global Status Report for Buildings and Construction. (For reference, it’s reported that a 1% increase represents 10 million more cars circling Earth’s equator.) But a drive for sustainability, stoked partly by recent government directives, has sparked a research front dedicated to minimizing these emissions.

When Malgorzata Zboinska, Ph.D., heard biomedical researchers were 3D-printing small objects like bio-based scaffolds for tissue growth with nanocellulose hydrogel, a substance made of nanocellulose and water, her interest was piqued. “I was prompted by the fact that the material has the ability to be 3D-printed,” said Zboinska, an architect-turned-academic at Chalmers University of Technology in Sweden. “Could one think about an architectural application of that material? A completely different field, a completely different scale?”

In a study published last year in the journal Materials & Design, Zboinska demonstrated the potential for hydrogel as an alternative to traditionally synthetic building materials such as resins, silicones, and acrylic paints. “My task is to showcase the [hydrogel’s] design potentials and the possibilities,” she said.

Researchers like Zboinska are considering the carbon footprint of construction life cycles — from the mining of raw materials, to the energy usage of manufacturing methods, to the end-of-life processes such as decomposability — to identify viable alternative building materials. Unlike many fossil-based materials, nanocellulose can be upcycled from forestry and agriculture waste, which would otherwise be discarded and can break down naturally at the end of its life. “There is quite a hype regarding upcycling,” Zboinska said. “Because combustion is no longer the solution if we are to save the planet.”

Nanocellulose is not new to the construction industry; the tiny particles have been found to help concrete sequester carbon and improve strength and durability in the curing process by retaining water. In 2017, the USDA reported its first full-scale test of concrete modified with nanocellulose after decades of research. But, according to Zboinska, this is the first time this nanocellulose hydrogel has been 3D-printed as a building material of its own.

Nanocellulose hydrogel looks like unset Jell-O, and, as with most hydrogels, it holds its shape when printed despite consisting of about 97% water. “The nanocellulose forms a network that kind of holds the water together,” said Johan Foster, Ph.D., a materials scientist and associate professor at the University of British Columbia who was not affiliated with this study. Objects printed for biomedical uses are generally small and meant to remain in a wet state. However, to be suitable for architecture, nanocellulose hydrogel must demonstrate its functionality in larger, dry forms.

To investigate, Zboinska added algae to her hydrogel recipe to help keep the final products flexible as they dried and devised a series of geometric patterns to determine how different designs, textures, and thicknesses affected shrinkage and deformation. She started small, printing test panels about the size of a credit card with a desktop 3D printer. Then, she upscaled her designs, creating larger pieces about the size of an open textbook using a printer with an agile robotic arm. Because nanocellulose hydrogel can be 3D-printed using only air pressure — essentially squeezed out of a syringe without heat — Zboinska could print objects at room temperature. This makes the process more energy-efficient than 3D-printing plastics or bioplastics such as corn-based polylactic acid, which require heating to nearly 400 degrees Fahrenheit (200 degrees Celsius).

Zboinska found that a thicker application of hydrogel led to more shrinkage and a tightly packed design led to more deformation. Neither result is more or less successful; understanding how the hydrogel behaves in different forms could help architects optimize designs depending on their intended use. “It’s more sturdy when it’s thick, but when it’s thin, it also has a certain flexibility,” she said.

While Zboinska’s findings contribute to nanocellulose hydrogel’s design potential, the product will eventually need to go through testing to meet safety standards set by international organizations. For one thing, it will have a shorter lifespan.

“Nature has a lot of ways to chew up cellulose, and it will naturally break down,” said Foster, adding that degradation time would vary depending on environmental conditions. “But think along the same lines as wood,” he said. “A two-by-four is very biodegradable, but when used inside of a wall, it’s got shielding on the outside, and that makes it not biodegrade.”

To increase longevity, some engineers have added components like plastic to otherwise biodegradable materials. This will be a challenging balance, Zboinska said, as the material must meet building requirements, yet too many artificial additives would compromise sustainability goals.

Both the industry and consumer sides will present hurdles to its wider adoption. The construction sector is slow to adopt new practices, said Jose Pinto Duarte, Ph.D., director of the Stuckeman Center for Design Computing at Penn State University. “Buildings are very expensive. It’s a huge investment, so people tend to be careful,” he said. “[Change] starts with small projects, demonstrating the potential, and then it goes up in scale.”

Some architects believe a bigger shift in how the construction industry thinks about the lifespan of buildings is needed. “Some buildings are designed to last forever; other buildings are designed just to last for a few years,” Duarte said, referring to structures such as on-site temporary work housing. “And, with lifestyle changes, the technology changes. So it’s normal that the buildings are replaced.”

Zboinska says she is continuing to develop the hydrogel recipe. In a recently funded research project, she is looking to test other bio-based ingredients in the mix, including yeast, and her work is beginning to attract broader interest. “It’s in the phase of showcasing what you can do and awakening interest and gaining momentum,” she said.

The field of bio-based construction materials is still in its infancy, but Zboinska is optimistic about its future: “We need to do something about the way we build to mitigate climate change. There is still hope in these materials.”