Dividing seawater presents a route for eco-friendly cement fabrication
A groundbreaking approach to cement production could transform it from a carbon emitter to a carbon absorber, resulting in a carbon-negative version of this building material, according to a report published on March 18, 2021, in Advanced Sustainable Systems. This new process could potentially expand to the production of various carbon-sequestering products such as paint, plaster, and concrete.
The manufacturing of cement contributes significantly to global carbon dioxide emissions, accounting for approximately 8% of total CO2 emissions, making it the fourth-largest emitter worldwide. The carbon emissions are largely due to mining for cement's raw materials in mountains, riverbeds, and ocean floors.
Researchers from Northwestern University in Evanston, Illinois, and Cemex's innovation development branch in Brügg, Switzerland, collaborated to develop a greener alternative to traditional cement. The team employed seawater electrolysis, a technique that uses electricity to break apart seawater's molecules, generating hydrogen gas, chlorine gas, and oxygen, as well as some minerals, including calcium carbonate, which is the primary raw material for cement production.
Scientists who have previously used seawater electrolysis for hydrogen gas production often view the mineral production as a nuisance, as it can obstruct the electrolysis equipment. However, this mineral production could prove beneficial for sustainable cement production.
Currently, the rate of electrolysis-based mineral production is too slow to meet industrial demands. Therefore, the team from Northwestern University investigated how these minerals form during electrolysis and explored ways to expedite the process and increase the yield.
By adjusting the applied voltage and injecting carbon dioxide gas into seawater at different rates and volumes, the researchers were able to alter the pH of the water. These changes affected the volumes, chemical compositions, and crystal structures of the precipitating minerals, making them flakier, more porous, or denser.
Their experiments suggest that it is possible to adjust seawater electrolysis to produce a variety of minerals and aggregates that the construction industry could use. If the energy source for the electricity is renewable, these materials could be not just carbon-neutral, but carbon-negative, as they would trap atmospheric carbon dioxide for periods lasting up to thousands of years.
Insights
Advances in seawater electrolysis technologies are paving the way for a carbon-negative or low-carbon production of cement and other construction materials. These approaches, such as the Zero CArbon Lime (ZeroCAL) method, combine seawater electrolysis with innovative processes to produce hydrogen and zero-carbon lime, a crucial precursor for cement. If powered by renewable energy, these methods can significantly reduce the carbon footprint of cement and lime production, potentially rendering it carbon-negative through carbon capture and utilization or mineralization processes. Additionally, the hydrogen produced can be used in other carbon-negative applications, such as the synthesis of green ammonia or e-methanol for clean fuels in various transportation sectors. Moreover, the electrolysis process can support the production of other construction materials by enabling the extraction and concentration of specific ions from seawater or brines, promoting circular and low-carbon manufacturing.
- The carbon-negative version of cement production, through seawater electrolysis, has the potential to transform it from a significant carbon emitter to a carbon absorber.
- In the collaboration between scientists from Northwestern University and Cemex's innovation development branch, they aim to develop a greener alternative to traditional cement, using seawater electrolysis.
- The process of seawater electrolysis not only generates hydrogen gas but also produces minerals, including calcium carbonate, the primary raw material for cement production.
- Previous applications of seawater electrolysis for hydrogen gas production often viewed the mineral production as a hindrance; however, this mineral production could be beneficial for sustainable cement production.
- The slow rate of electrolysis-based mineral production currently limits its industrial use, but researchers at Northwestern University are investigating ways to expedite the process and increase the yield.
- By adjusting the applied voltage and injecting carbon dioxide gas into seawater at different rates, the researchers aim to control the pH of the water and alter the properties of the precipitating minerals for use in the construction industry.
- If powered by renewable energy, the minerals and aggregates produced through seawater electrolysis could not only be carbon-neutral but carbon-negative, as they would trap atmospheric carbon dioxide for thousands of years, contributing to climate change mitigation efforts.
