Coral reef and mach fish (Photo/iStock)
University
Carbon-negative production technique, inspired by reefs, develops durable building materials
EARTH MONTH: A USC research presents an electrochemical method that captures carbon dioxide to fabricate sturdy and fire-resistant materials.
A novel technique inspired by coral reefs captures carbon dioxide from the atmosphere and converts it into robust, fire-resistant construction materials, presenting a promising avenue for carbon-negative building practices.
This approach, formulated by USC scholars and elaborated in a study found in npj Advanced Manufacturing, takes cues from the inherent capability of ocean coral reefs to construct sturdy structures through the sequestration of carbon dioxide. The resulting mineral-polymer composites exhibit remarkable mechanical resilience, fracture toughness, and fire-resistant characteristics.
“This represents a crucial advancement in the development of converting carbon dioxide,” stated Qiming Wang, associate professor in civil and environmental engineering at the USC Viterbi School of Engineering. “In contrast to conventional carbon capture methods that aim at storing carbon dioxide or transforming it into liquid forms, we discovered that this innovative electrochemical manufacturing process translates the compound into calcium carbonate minerals within 3D-printed polymer structures.”
Inspired by coral reefs
Current carbon capture methods typically prioritize storing carbon dioxide or converting it into liquids. However, these approaches are often costly and ineffective. This innovative method proposes a more economical solution by directly incorporating carbon capture within building materials.
Wang credited the “remarkable nature of ocean coral” as a cornerstone of the study’s innovation. “Coral, as a living organism, utilizes photosynthesis to absorb carbon dioxide from the environment and convert it into a physical structure,” Wang noted.
The technique was specifically inspired by how coral produces its aragonite skeletal frameworks, referred to as corallites. In nature, coral fabricates corallites via a process termed biomineralization, whereby coral captures carbon dioxide through photosynthesis. This process combines the compound with calcium ions from seawater, leading to the precipitation of calcium minerals around organic templates.
The research group replicated this phenomenon by fabricating 3D-printed polymer scaffolds that echoed the organic templates of coral. Subsequently, these were coated with a fine conductive layer. The coated structures were linked to electrochemical circuits as cathodes and immersed in a calcium chloride solution.
Upon introducing carbon dioxide into the solution, hydrolysis occurred, breaking it down into bicarbonate ions. These ions then interacted with calcium within the solution to generate calcium carbonate, gradually filling the 3D-printed voids. This led to the development of the final product, a dense mineral-polymer composite.
Fire-resistant qualities
The most intriguing characteristic of the experimental composite material may be its performance in fire scenarios. While the 3D-printed polymer scaffolds themselves lack intrinsic fire-resistant features, the mineralized composites upheld their structural stability during the research team’s fire tests.
“The manufacturing process exhibited a natural fire-retardant mechanism allowing for 30 minutes of direct flame exposure,” remarked Wang. “When subjected to elevated temperatures, the calcium carbonate minerals emit small amounts of carbon dioxide that seem to have a fire-extinguishing effect. This built-in safety aspect offers significant benefits for construction and engineering sectors where fire resilience is vital.”
Alongside fire resistance, fractured fabricated structures can be mended by connecting them to low-voltage power. Electrochemical reactions can reconnect the fractured interfaces and restore their mechanical integrity.
A carbon-negative future
Following an exhaustive life cycle evaluation, the researchers established that the manufactured structures had a negative carbon footprint, revealing that the carbon capture surpassed the carbon emissions associated with production and operations.
The researchers also showcased how the created composites could be assembled into larger structures through a modular system, yielding substantial load-bearing constructions; the composite materials may potentially find applications in building and other fields requiring high mechanical resistance.
Wang noted the intention to focus on bringing the patented technology to market. Given that building materials and construction account for approximately 11% of global carbon emissions, the study’s innovative manufacturing technique sets the stage for the potentiality of carbon-negative structures.
About the study: In addition to Wang, the other authors of the study include Haoxiang Deng, Haixu Du, Ketian Li, Yanchu Zhang, Kyung Hoon Lee, and Botong Zheng of USC.
This investigation 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).