A research team has found that finely ground coconut-shell biochar can simultaneously increase carbon dioxide (CO₂) uptake and improve the mechanical performance of natural hydraulic lime (NHL). The best overall results were obtained by adding 2% biochar with a particle size of 325 mesh. Compared with unmodified NHL, this formulation increased compressive strength by 35.7% after three days and 10.9% after 28 days, while raising CO₂ uptake by 14.6% after six hours and 11.9% after 24 hours. The findings could support the development of lower-carbon, mechanically reliable lime materials for restoring historic buildings and constructing environmentally friendly, antique-style structures.