Circularity of building materials: A non-discriminating calculation methodology

The energy transition has shifted impacts to materials, their energy use and potential depletion. Especially affected is the building and construction sector, since it is the sector which has the largest consumption of materials. Therefore, it is of utmost importance that materials cycles be closed as well, that they stay within system boundaries, and that we use objective calculation and evaluation methods. If we look at organic or biobased resources, the basic impacts in their flow are obvious and can be characterised fairly simply: they grow on the basis of solar energy at a certain speed and volume per unit of land. It’s a constantly renewing flow, with use maximised to what naturally (re-)grows. In-depth analyses have created growing awareness that non-organic materials are also in fact renewable, even without human intervention but in different scales of time and volume, in time frames way beyond the normal planning horizons of humans. They are renewed by volcanic and tectonic movements of the Earth’s crust. The paper explores how non organic materials will renew, that is, become re-concentrated in the Earth’s crust. In fact it is the concentration that is crucial for effective use, without additional energy input that would deplete other sources. From this analysis it follows that all resources can be characterised by the speed and volume in which they concentrate—either by the soil and solar route, or by the Earth movement route. : “Resources can thus be grouped into four categories: regrowable, streaming, slow and synthetic. The characterisation shows a similar pattern in other indicators for these resources: the slower the resources are regenerated, the more (embodied) energy required to obtain the resources, for instance. This is an attempt, a pre-study, to set up a methodology, and the first estimations for the global flows of resources in different categories. In the end it turns out that all resources have a natural renewal basis, and that there are no sustainable or non-sustainable (or non-renewable) resources: it is their use, within maximised flows, that determines their sustainability. It requires that we re-define the notion of ‘circular’.