Egyptian researchers cut brick heat transfer by half using eggshell waste

In 2025, researchers in Egypt conducted experiments adding powdered eggshell waste to fired clay bricks. After cleaning, drying and grinding the shells, they mixed the powder with clay from the Kharga Oasis in ratios from 1% to 10% and fired the bricks at 1,100 °C. The bricks with a 10% eggshell content achieved a 50% reduction in thermal conductivity and roughly a 30% decrease in both thermal diffusivity and effusivity, indicating superior insulating performance.

This improvement is attributed to pores formed when calcium carbonate in the shells decomposes and releases carbon dioxide during firing. The results could benefit structures in hot climates by limiting heat flow, and they offer a recycling avenue for the estimated 110 billion eggshells that end up in landfills each year.