"Electrochemical Synthesis of Calcium Silicate Hydrate for Low Carbon Cement" ACS Energy Letters
As the world works to alter the trajectory of climate change, most attention focuses on reducing humanity's reliance on fossil fuels and lowering greenhouse gas emissions. Yet a major source of carbon dioxide (CO2) is cement production, which accounts for 8% of global CO2 emissions. Now, researchers reporting in ACS Energy Letters have manufactured cement that lowers input energy demand by 70% and reduces CO2 emissions by 98% compared with traditional production methods.
This work defines an electrified path for cement production that could reduce the industry's massive carbon footprint by as much as 98% when using waste cement as a feedstock." - Curtis Berlinguette
"Our team was motivated to address cement production emissions at the source," says Curtis Berlinguette, the corresponding author of the study. "We used electricity and recycled cement to make precursors that formed a type of cement called belite at lower temperatures than were previously known. Belite-rich cement is important for massive structures like dams."
Cement is an essential ingredient for making concrete a durable construction material, because when mixed with water, it strongly binds sand and gravel. And the starting material for cement is typically limestone. However, producing cement traditionally demands a great deal of energy as limestone (made of calcium carbonate, or CaCO3) and silica-containing minerals are heated in two stages to more than 2,600 degrees Fahrenheit (1,450 degrees Celsius). These processes release significant amounts of CO2 as a by-product when limestone breaks down.
Taking a different approach, Berlinguette and a research team at the University of British Columbia used electricity to lower the energy requirements of the chemical conversion of limestone and silica into a cement precursor. The electrochemistry approach allowed the reaction to take place at 140 F (60 C). The product of this reaction was then converted into belite in a kiln at 1,200 F (650 C). The lower temperatures of this new method reduced the thermal energy required by 70% as well as cut CO2 emissions compared to the traditional processes.
To further reduce emissions, the team tested the electrochemistry process on recycled waste cement, using it instead of limestone. This demonstration dropped emissions of the new method to 20 kilograms CO2 per ton - a 98% reduction in emissions compared to the 800 kilograms CO2 per ton cement released during conventional processes.
The researchers note that the electrochemical reactions produced hydrogen, which could be burned to provide the thermal energy for the second step of cement production, thus replacing fossil fuels.
The authors acknowledge funding from the New Frontiers in Research Fund, Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, Canadian Institute for Advanced Research, Canada Research Chairs, and Canada First Research Excellence Fund.
The University of British Columbia has filed an international patent application about the process in this work, and two authors are co-founders of a company commercializing the technology.
