reference book "Ökologisches bauen"

Chapter Building Materials:

The choice of building materials is, in many aspects, an ecological issue. Here, most people think of timber, wool and clay. Because of their natural origin, they appear to be not harmful to health and environment, while also apparently easily obtained. For example, there is clay can be found all over the world. It is an ancient building material too.
Actually, there are two important topics to be mentioned in this regard and these are pollutants and resources. There is an unmanageable quantity of building materials and therefore a diversity too of pollutants and damaging substances.
Particular attention is paid to waste, carbon dioxide emission and primary energy input during production and processing. These attributes are deemed to be the “footprint” of a building material.