Learning from Oysters Makes Better and Greener Cement
Cement Causes Greenhouse Gasses
Concrete is everywhere, Scientific American opined. Companies make more concrete than any other material on Earth, and that volume is rising because of global development. Cement, the binder that holds the sand or crushed stone in concrete together, is one of the most energy-intensive products on the planet. In traditional processes, limestone is baked at up to 1,450 degrees Celsius (2,640 degrees Fahrenheit) in enormous kilns that are fired almost exclusively with fossil fuels, Making one kilogram of cement sends one kilogram of CO2 into the atmosphere. Cement and concrete production generate up to 9 percent of all human CO2 emissions.
As a result, Eco-Business reported, the cement industry faces increasing pressure to reduce its carbon footprint and shift to sustainable practices. Strategies so far have included retrofitting plants, deploying carbon capture technologies and embracing low-carbon cement.
There is Momentum towards Change
That momentum for change stems from factors increasing regulatory pressure on carbon emissions, shifts in consumer awareness and evolving construction standards. As more countries adopt green building certification programs, OpenPR noted, the appetite for eco-friendly construction materials will continue to grow.
The WEF said cement and concrete operations currently have a high dependency on natural resources. Companies that can get ahead of the risks of nature loss can be prepared for incoming policy and regulatory requirements, and they can minimise disruption from nature-related physical, transition and systemic risks.
However, much of what is called green cement is not really green. The green cement market is currently segmented into solutions based on fly ash, slag or recycled aggregates. The processes have high production cost due to the technologies used in manufacturing, such as cost-intensive heat recovery and chemical mixtures. Still, the global green cement market is projected to surge from US$34 billion in 2025 to US$68 billion by 2032, with more coming from bio-cement made from microbial processes and agri-waste.
A variety of organisations have even published roadmaps for the transition. The Global Cement and Concrete Association (GCCA), which represents 80 percent of the global cement industry by volume outside of China, has developed a biodiversity and water policy. The Portland Cement Association created a roadmap to carbon neutrality. And Business for Nature’s Nature Strategy Handbook offers a step-by-step guide to develop a nature strategy.
Companies and Academics have Biomimicry Solutions
It turns out that there actually are better solutions that do produce green cement. A number of them use processes inspired by shells of sea creatures such as molluscs, oysters and abalone.
Northwestern University, for instance, said its scientists have developed a new carbon-negative building material using seawater, electricity and carbon dioxide. The strategy locks away CO2 permanently and turns it into valuable materials, which can be used to manufacture cement, as well as concrete, plaster and paint. The process also releases hydrogen gas, a clean fuel. The scientists, in collaboration with Cemex, devised an alternative approach to source sand by harnessing electricity and CO2 to grow sand-like materials in seawater rather than digging into the earth. Associate professor Rotta Loria likens the process to the technique coral and mollusks use to form their shells, which harnesses metabolic energy to convert dissolved ions into calcium carbonate.
At Princeton University, a research team led by assistant professor Reza Moini developed a new cement composite material that is more crack-resistant and flexible than standard cement. The inspiration for this innovative cement composite similarly came from oyster and abalone shells. The Princeton Materials Institute also said the new cement composite is 17 times more crack-resistant than standard cement and 19 times more able to stretch and deform without breaking.
TechXplore said Prometheus Materials’ production of building materials starts with providing microalgae with what they need to do what they do naturally: biomineralization, the process of living organisms producing minerals that form structures such as shells and reefs. The microalgae produces the minerals using photosynthesis, powered by the sun. The company uses seawater to grow a culture of microalgae and create the mineral. When water is removed, what's left is bio-cement. It is combined with rocks and sand to form concrete.
Design News said a team in MIT’s Department of Civil and Environmental Engineering is also developing a new way to build cement paste, the binding ingredient in cement, by examining the structure and properties of natural materials such as bones, shells and deep-sea sponges. Researchers chose these materials because of their exceptional strength and durability.
Another is Biomason, where the core technologies are used to create Biocement. Bacterial spores are introduced into a mix of gravel, sand and nutrients to convert calcium and carbonate into Biocement, a biologically forged calcium carbonate made of the same material as eggshells, coral skeletons, seashells and limestone. Rather than burning limestone and releasing CO2, Biocement forms through multiple biological processes that reduce carbon emissions by more than 90 percent.
This is not to say that mimicking the production of shells or eggshells is the only solution. Other companies and researchers have based their innovations on things such as plants.
In Australia, for instance, the ISAAA said researchers from the University of South Australia found that enzymes from an invasive weed known as paddy melon could be used for developing bio-cement. This discovery shows potential for the construction, mining, and forestry industries.
Another is Sublime, which has developed a proprietary process that uses an electrolyser to produce cement at ambient temperatures. ESG Today said Sublime, spun out of MIT in 2020, replaces energy and fossil fuel-intensive kilns and enables the use of calcium sources as an input material, avoiding the release of CO2 from limestone.
While producing cement today using traditional processes has high energy costs and negative environmental impacts, innovations based on nature could soon provide far more cost-effective and sustainable solutions.
