A 'carbon negative' concrete invention removes CO2 from the air during production

What if the billions of tons of concrete poured around the world every year could also help fight climate change emissions? Washington State University researchers say they have developed an environmentally friendly way to create "carbon negative" concrete that removes carbon dioxide from the air. Concrete usually requires high temperatures and burning fuels, and the limestone used as an ingredient produces carbon dioxide when it decomposes. It is estimated that the 4 billion tons of concrete produced each year worldwide are responsible for 8% of annual human carbon dioxide production. But the WSU team created a formula that uses 30% of biochar—a type of charcoal made from organic waste—that, when mixed with concrete wastewater, can remove up to 23% of its weight of carbon dioxide from the air while maintaining similar strength to regular cement. Current methods of using biochar in concrete found that the strength of concrete was significantly reduced even when using 3%. But when added to concrete wastewater, the resulting paste achieved a compressive strength of about 4,000 pounds per square inch after 28 days compared to regular cement, the researchers said.