Carbon-negative manufacturing method creates strong building materials

A new method inspired by coral reefs can capture carbon dioxide from the atmosphere and transform it into durable, fire-resistant building materials, offering a promising solution for carbon-negative construction.

The approach, developed by USC researchers and detailed in a study published in npj Advanced Manufacturing, draws inspiration from the ocean’s coral reefs’ natural ability to create robust structures by sequestering carbon dioxide. The resulting mineral-polymer composites demonstrate extraordinary mechanical strength, fracture toughness and fire- resistance capabilities.

“This is a pivotal step in the evolution of converting carbon dioxide,” said Qiming Wang, associate professor of civil and environmental engineering at the USC Viterbi School of Engineering. “Unlike traditional carbon capture technologies that focus on storing carbon dioxide or converting it into liquid substances, we found this new electrochemical manufacturing process converts the chemical compound into calcium carbonate minerals in 3D-printed polymer scaffolds.”

Inspiration of coral reefs

Existing carbon capture technologies generally focus on storing carbon dioxide or converting it into liquid substances. However, this is generally expensive and inefficient. This new method offers a less expensive solution by integrating carbon capture directly into building materials.

Wang attributed the “magic of ocean coral” as fundamental to the study’s breakthrough. “As an organism, coral can use photosynthesis to capture carbon dioxide from the atmosphere and convert it into a structure,” Wang said.

The method was directly inspired by how coral creates its aragonite skeletal structures, known as corallites. In nature, coral builds corallites through a process called biomineralization, in which coral sequesters carbon dioxide from the atmosphere by the process of photosynthesis. It then combines the chemical compound with calcium ions from seawater to precipitate calcium minerals around organic templates.

The research team replicated this process by creating 3D-printed polymer scaffolds that mimicked coral’s organic templates. They then coated them with a thin conductive layer. These coated structures were then connected to electrochemical circuits as cathodes and immersed in a calcium chloride solution.

When carbon dioxide was added to the solution, it underwent hydrolysis to be broken down into bicarbonate ions. These ions reacted with calcium in the solution to form calcium carbonate, which gradually filled the 3D-printed pores. This resulted in the final product, a dense mineral-polymer composite.

Fire resistance

The most surprising trait of the experimental composite material may be its reaction to fire. While the 3D-printed polymer scaffolds lack inherent fire-resistant properties, the mineralized composites maintained their structural integrity under the research team’s experimental flame tests.

“The manufacturing method revealed a natural fire-suppression mechanism of 30 minutes of direct flame exposure,” Wang said. “When exposed to high temperatures, the calcium carbonate minerals release small amounts of carbon dioxide that appear to have a fire-quenching effect. This built-in safety feature provides significant advantages for construction and engineering applications where fire resistance is critical.”

In addition to fire resistance, cracked fabricated structures can be repaired by connecting them to low-voltage electricity. Electrochemical reactions can rejoin the cracked interfaces and restore the mechanical strength.

Carbon-negative future

After a rigorous life cycle assessment, the researchers found that the manufactured structures featured a negative carbon footprint, revealing that the carbon capture exceeded the carbon emissions associated with manufacturing and operations.

The researchers also demonstrated how the manufactured composites could be assembled into larger structures using a modular approach, creating large-scale load-bearing structures; the composite materials could potentially be used in construction and other applications requiring high mechanical resistance.

Wang said the researchers plan to focus on commercializing the patented technology. With building materials and construction responsible for around 11% of global carbon emissions, the study’s new manufacturing method lays the groundwork for the possibility of carbon-negative buildings.

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About the study: In addition to Wang, other study authors include Haoxiang Deng, Haixu Du, Ketian Li, Yanchu Zhang, Kyung Hoon Lee and Botong Zheng of the University of Southern California.

This research was supported by grants from the Office of Naval Research (N00014-22-1- 2019) and the National Science Foundation (CMMI-1943598, CMMI-2229228 and DBI- 2222206).