The century of material stockpiling: 23-fold increase in material stocks in buildings and infrastructure drives resource consumption

A team of researchers led by scientists from the Institute of Social Ecology at AAU has recently presented the first global estimate of the volume of natural resources accumulated in buildings and infrastructure. According to their calculations, global in-use stocks of materials rose 23-fold between 1900 and 2010, harboring long-term consequences for loop closure and emissions.

“The 20^th century is frequently characterized by the emergence of the throwaway society. Our result indicates that, somewhat paradoxically, the description as a century of material accumulation is more to the point”, lead scientist Fridolin Krausmann explains. Together with his team, he has calculated magnitude, dynamics and effects of resource utilization (steel, copper, aluminum, timber, concrete, sand, gravel, etc.) for all societal stocks like buildings, infrastructure, machinery and cars.

The researchers demonstrate that the growing mass of socioeconomic material stocks plays a crucial but under-appreciated role in the context of achieving a more sustainable use of resources. The reason is that material stocks determine energy demand and emissions as well as the volumes of waste and recycling potential in the long run. To quantify these effects, the research team has developed a dynamic model depicting global material stocks and the related flows of materials.

The study yields impressive results: “We were able to show that meanwhile around half of all materials extracted globally each year are used to build up or renew in-use stocks”, Dominik Wiedenhofer explains. Between 1900 and 2010, global material stocks grew 23-fold, reaching a current value of 800 billion tons, two thirds of which are in the industrialized nations.

Fridolin Krausmann expands: “Although there are intensive efforts to close material loops, thus improving recycling rates, these remain very low: Only 12 % of materials flowing into stocks comes from recycling. In part, this is due to the fact that we currently invest four times more material in building up stocks than emerges as waste flow on the other side.” And yet, the potential for recycling is huge: Stocks are aging and in the next 20 years alone there could be as much as 270 billion tons of demolition material. This is equivalent to the volume accrued over the previous one hundred years. This material will either have to be treated and deposited at high cost, or it can regain value in a circular economy.

Overall, global material stocks are, however, set to continue to grow. While the dynamics have lost some momentum in the industrialized countries, stocks in emerging economies are growing rapidly, with China at the forefront. “If all countries across the globe are to catch up to the level of per capita stocks of the industrialized nations, this would lead to a further quadrupling of stocks”, Dominik Wiedenhofer expounds. Not only does this require vast quantities of raw materials, but it would also result in a massive rise in energy consumption and subsequent CO₂ emissions threatening the climate goals agreed in Paris.

The authors of the study argue that, a more sustainable use of resources requires a decoupling of economic growth from stock growth by intensifying the use of existing infrastructure and buildings, extending utilization periods, more efficient design, and optimal loop closure.

Krausmann, F., Wiedenhofer, D., Lauk, C., Haas, W., Tanikawa, H., Fishman, T., Miatto, A., Schandl, H. & Haberl, H. (2017). Global socioeconomic material stocks rise 23-fold over the 20th century and require half of annual resource use. PNAS, http://www.pnas.org/content/early/2017/01/31/1613773114.abstract.