Although pictures of long beaches and high dunes convey a different impression, sand is a finite resource. Quarrying sand can have dire consequences, and can even lead to the erosion of entire coasts. Together with strategic partners from industry, the start-up sZaaK Technologies wants to establish flue ash as an alternative. With the help of a patented procedure, the ash is converted such that it can completely replace natural sand in building materials such as concrete, mortar, and plaster. What is more, the recycled variant is lighter and more durable and has better sound and heat insulation.