My work develops a pure lime plaster from mussel shell waste, which is otherwise incinerated with the residual waste. The project shows how invasive species can be transformed into regional resources for sustainable architecture. The shells, rich in calcium carbonate, offer an alternative to limestone mining, reduce CO₂ emissions and avoid waste problems. Regional availability creates local design. The shell limestone plaster produced from this material impresses with its negative CO2 balance, positive spatial properties and aesthetic surface textures.