University of Wisconsin’s Clean Energy Community Initiative hosted UW College of Engineering Associate Professor Bu Wang, PhD, for a talk about his research on new carbon-negative cement replacements. The talk, titled Removing Carbon, Building Futures: Cement Decarbonization and Energy Synergies, was hosted as part of CECI’s Sustainable Future Seminar Series.
In order to reach climate goals, it’s not enough to reduce carbon emissions, according to Bu. Greenhouse gases are already in the Earth’s atmosphere, so it’s important to develop carbon-negative technologies that not only don’t produce more carbon but also remove pre-existing carbon emissions, Wang said.
“[To reach] our climate goal [it] is not only enough to stop the emission, we actually need to pull some CO2 emission from the air. That’s what’s called carbon removal,” Wang said.
That’s where his technology comes in. For each ton of cement, 0.85 tons of carbon dioxide emissions are made, because making cement requires high temperatures, Wang said. Cement production currently accounts for 7% of global carbon dioxide emissions. By comparison, transportation by passenger cars makes up 8%, according to Wang.
Currently, carbon emissions from cement production are lowered by mixing in 20-30% of coal fly ash. Because coal fly ash is a byproduct of electricity generation, its carbon emissions have already been accounted for in the electricity generation process, according to Wang. Wang and his research team have developed something different, called coupled direct capture and mineralization.
They developed a solvent that captures carbon dioxide from the air and then they use a low-energy chemical reaction to pull the carbon dioxide out of the solvent. This regenerates the solvent to pull more carbon dioxide and simultaneously turns the gaseous carbon dioxide into a solid called CO2 mineralization, Wang said.
This mineral waste can actually be used as a cement replacement, according to Wang. This not only bypasses the need for carbon-intensive cement production but also removes existing carbon dioxide in the process, according to Wang.
“We can regenerate the solvent using low energy input. Simultaneously, we can convert some mineral waste into a carbon-negative cement replacement,” Wang said “There’s a chance we can actually replace all the cement [with this replacement] when making concrete.”
Because this process has real-world improvements and can be scaled up industrially, it answers the “why” of reducing carbon emissions, according to Wang.
Simply saying something will decrease or remove carbon emissions isn’t enough – there has to be a good rationale for the specific technology in the specific situation in order for the idea to be backed, Wang said.
“Why do you want to do a particular thing to reduce your carbon footprint — that’s the question I think we always want to ask, because if you find the right incentive for people to reduce their carbon emission, [it] can happen really fast,” Wang said.
