Digital library of building materials sustainability, and 'passports'. Madaster is the online registry for materials and products. In Madaster, data are recorded on all materials and products that are incorporated in a real estate or infrastructure object, such as buildings and bridges.  Registering every component provides insight, for example, into the degree to which an object can be dismantled, embodied carbon, or the toxicity of the materials and products used. It also enables determining whether materials and products can be reused after disassemblage. Building in such a circular way means that we are drastically reducing the amount of waste and CO2 emissions and are taking better care of our planet.