Human Waste Biochar Makes Stronger Concrete in Lab Tests

Researchers in India and the United States found that replacing part of the cement in concrete with biochar made from treated fecal sludge can increase strength in laboratory tests. A 10% replacement raised compressive strength by 21% and flexural strength by 42% after 91 days compared with conventional concrete. A 5% replacement also improved both measures and performed better on water absorption, porosity, and drying shrinkage. Because cement production accounts for roughly 7% of global carbon dioxide emissions, partial replacements like this could cut the amount of cement needed in concrete. The researchers note that the full carbon impact still depends on the energy used to pyrolyze the sludge and on transport and treatment steps. Durability under freeze-thaw cycles, salinity, and extreme temperatures still needs real-world testing before the material is ready for construction.