Coral inspires CO2 capturing building materials

Described in npj Advcanced Manufacturing, the new technique was developed by engineers at the University of Southern California (USC). It replicates the biomineralisation process that coral reefs use to grow, sequestering carbon dioxide from the atmosphere.

The USC team first created 3D-printed polymer scaffolds that mimic coral’s organic templates and coated them with a thin conductive layer. These 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 and was broken down into bicarbonate ions. These ions reacted with calcium in the solution to form calcium carbonate, which gradually filled the 3D-printed pores. The final product was a dense mineral-polymer composite.

“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.”

One surprising discovery to emerge from the study was the new material’s resistance to fire. Despite the polymer scaffolds lacking fire-resistant properties, the mineralised 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,” said Wang. 

“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.”

Lifecycle assessments found that structures made from the composite had a negative carbon footprint, with captured carbon exceeding the emissions associated with manufacturing and operations. The USC team also demonstrated how the composites could be assembled into larger structures using a modular approach, creating large-scale load-bearing structures.

Wang said the researchers now plan to focus on commercialising the patented technology.