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New Concrete Absorbs More CO2 Than it Emits

Concrete is one of the most common materials on Earth, thanks to its high strength and low cost, but it’s also one of the largest single sources of CO2 emissions - roughly 8 percent of humanity’s total carbon dioxide emissions. So, any reduction in concrete emissions would be very good news, but engineers at Washington State University (WSU) have really upped the ante by developing a new method for making concrete that absorbs more carbon than it emits.


Concrete pillars

The process of making cement requires very high temperatures, and that usually requires burning fuels which, of course, emits CO2. That can be partly offset by switching to renewable energy sources, but chemical reactions in the mixture also release huge amounts of CO2, and this is harder to avoid.


Scientists around the world have been tweaking the formula to try to reduce concrete’s carbon footprint, but the WSU researchers investigated a new method involving biochar, a charcoal made from organic waste. While biochar has been added to cement before, this time the team treated it first using concrete washout wastewater. This boosted its strength and allowed a higher proportion of the additive to be mixed in.


In experiments, the team created cement that contained 30 percent treated biochar, and found that the resulting concrete was carbon-negative - it actually absorbed more carbon dioxide than was emitted during production of the material. The research was published in the journal Materials Letters.


Better yet, the new concrete would be expected to continue absorbing CO2 during its working lifetime of several decades. More testing is still to be done, but this is very promising...

 

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