CASCO, or Carbon Sink Construction, aims to create an ecosystem for scaling up the use of local and natural building materials in the border region. These materials act as carbon sinks (absorption of carbon-containing compounds), helping to reduce CO2 emissions from new construction projects. The project aims to make building with local and natural materials the standard for construction professionals. To achieve this goal, the project targets both the demand and supply side of the market. Specific actions include developing chains for local economies, analysing the CO2 emissions and environmental impact of construction projects, determining the CO2 storage capacity of building materials, promoting a clear CO2 standard in the construction sector, and disseminating knowledge to construction professionals and the general public.