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 new approach to carbon-negative construction 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-resistant 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.”
The role of coral reefs in carbon-negative manufacturing
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 of carbon-negative construction offers a less expensive solution by integrating carbon capture directly into building materials.
It was directly inspired by how coral creates its aragonite skeletal structures, known as corallites.
In nature, coral builds corallites through a process called biomineralisation, in which coral sequesters carbon dioxide from the atmosphere by the process of photosynthesis. Then, it 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.
Benefits of fire-resistant materials
The most surprising trait of the experimental composite material was its reaction to fire.
While the 3D-printed polymer scaffolds lack inherent fire-resistant properties, the mineralised composites maintained their structural integrity under the research team’s experimental flame tests.
“The carbon-negative 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 re-join the cracked interfaces and restore mechanical strength.
The future of carbon-negative construction
After a rigorous life cycle assessment, the researchers found that the manufacturing method 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 concluded that the researchers plan to focus on commercialising the patented technology.
With building materials and construction responsible for around 11% of global carbon emissions, the study’s new carbon-negative manufacturing method lays the groundwork for the possibility of carbon-negative buildings.
