Scientists Are Making Concrete With Human Poop – And It Gets 42% Stronger

This is a well-written and approachable article by Michelle “Chelle” Starr, Head Journalist at ScienceAlert, who has spent more than 15 years covering science and technology. (ScienceAlert) Starr explains new research from India showing that concrete can be made partly with biochar produced from treated human fecal sludge, potentially turning a difficult waste stream into a useful building material.

Researchers dried the sludge, heated it in a low-oxygen environment, ground the resulting biochar into powder, and used it to replace 5%, 10%, or 15% of the cement in conventional concrete. The 5% mixture produced the strongest overall results, while the 10% mixture showed gains of up to 42% in flexural strength after 91 days.

The biochar appears to improve concrete by storing and slowly releasing water during curing, contributing silica that helps form strength-giving compounds, and filling microscopic gaps in the material. Lower concentrations also reduced porosity, water absorption, and shrinkage, although the 15% mixture began to perform worse.

The idea could eventually reduce cement consumption while putting sewage waste to productive use, but it remains experimental. Researchers still need to study real-world durability, heavy-metal leaching, performance under extreme conditions, and whether the process actually produces a meaningful reduction in carbon emissions.