13. Anthropogenic Stock as a Source of Raw Materials: Optimized Utilization of Recycled Building Materials to Conserve Resources

Owing to the valuable materials contained in existing buildings and infrastructure installations, these represent an enormous source of raw materials for future generations. In residential buildings alone, the “anthropogenic stock” has meanwhile reached an order of magnitude of almost ten billion tons. Of these, bricks and concrete represent the major part. In contrast, the quantity of construction and demolition debris generated per year amounts to about 50 million tons. Of these, however, only a minor share is recovered by means of high-quality recycling and reused in building construction as concrete aggregate, thus replacing natural gravel. Given the demographic development, continued internal migration and a foreseeable change in housing requirements, demolition and refurbishment will result in a significant increase in the quantities of construction and demolition debris generated in many regions of Germany. It will be necessary to return these wastes to substance cycles that are of the highest possible quality. Therefore, issues to be clarified will include the development of the respective regional building material requirements and quantities of construction and demolition debris generated, potential obstacles to the use of resource-saving recycled concrete, and how initial flagship projects were able to bring about an increase in the acceptance and use of recycled concrete in a rather practical way.