Mr. Pohl, how circular is the construction industry today?

The importance of resource efficiency and circular economy has increased in recent years. The mineral-based construction industry already has high recycling rates in principle: The waste fraction of construction waste is almost completely recycled and almost 80% is sent for recycling. However, most of the mineral waste fraction that is currently generated is returned to road construction and earthworks. In other words, it is not recycled at a high value-added stage comparable to that of the original product, even though this would be technically possible in principle. In my view, however, a true recycling loop is only created when the material is fed back into the cycle at a comparable value-added stage. In other words, a masonry block becomes a masonry block again, for example.

What are the challenges here?

A true circular economy can only work if there is a functioning interaction between technology, the market, and the law. The challenges here are less in the technical or technological area, but rather in the legal area. The building materials industry is still dealing with considerable (waste) legal obstacles, e.g., regarding the waste status of potential secondary raw materials.
In addition, there is the challenge on the market side that manufacturers of building materials and building products cannot assume that the availability of demolition waste and secondary raw materials can be planned. This is mainly due to a data gap: There would need to be a cadaster showing how many raw materials are contained in the respective building, how old the building is and when the raw materials could be returned to the cycle.

How can this be solved?

In addition to the building energy law, there is the idea of a resource law combined with the obligation to feed data from construction projects into a cadaster as well. Digital solutions such as BIM could play an important role here. After all, in the digital planning of projects, all the data and information required throughout the life cycle of a building should be recorded anyway.

What will drive the move toward more sustainable construction in the coming years?

Something will happen because something must happen. The tasks of the new government are on the table: climate protection, adaptation to climate change, resource efficiency, building resource law.
At the EU level, the EU taxonomy comes in as a driving factor: in the assessment criteria for sustainable investments and economic activities, the building sector is explicitly addressed - with concrete technical assessment criteria in which resource efficiency and the handling of construction waste from deconstruction projects also play a role. For all those who have to be "assessed" according to the EU taxonomy, i.e., are subject to certain disclosure obligations, the topic of circular economy is in any case directly relevant.

What is important in the assessment?

For the CO2 balance of buildings, it is crucial to consider the entire life cycle of the different construction methods, to balance them in accordance with standards and to verify the results externally. Over the life cycle, the CO2 emissions of wood and aerated concrete construction methods, for example, are roughly the same, as we calculated in the joint study with Xella T&F. At present, the decisive factor for the CO2 footprint over the entire life cycle is not the construction method, but the energy quality of a building and how energy is supplied during the utilization phase.

What kind of role does the availability of resources, for example wood, play?

Even today, Germany is dependent on wood imports on balance, and this will not change much in the future in realistic scenarios. In a study by the Federal Environment Agency from 2020, for example, it is worked out that the coniferous wood potential, which is currently still decisive for the construction sector, is and will be too small to cover domestic wood use, insofar as a need for imports will remain.

Could one say: for this reason alone, the circular economy must be expanded even more?

Not only with wood, with all raw materials there are challenges here that need to be solved in the long term. Climate change means that renewable raw materials have to be reshaped. For example, our forests must become more robust; monocultures are a particular problem here. In the case of mineral raw materials, the issue is less the raw material deposits and more the competition for the areas of possible extraction sites.
In other words, we need to build closed cycles now - and with future generations in mind!

What is important in the analysis and evaluation of construction methods from the point of view of the circular economy?

Here, too, it is important to consider the entire life cycle. And: The requirements for components and buildings must determine the construction and design methods, and not vice versa. It is not acceptable that certain building materials and construction methods are politically promoted and subsidized just for the sake of the building material.

For the end consumer, the issue of sustainability has so far rarely been a real selling point. Is that changing from your perception?

Of course, cost efficiency still plays an important role in many cases. But I observe that, especially in commercial real estate, the sustainability of a building or a lack of sustainability quality has now become a "red flag." Anyone who can't deliver on this will have a harder time in marketing processes.

How realistic is a zero-emission house?

In principle, it can already be built today. It all depends on the triad. The building must be thought of together with its site and its roof surfaces and areas outside. How much energy can I generate myself? What else can I do to consume as little energy as possible - key words: thermal insulation, efficiency of technical systems and options for integrating renewable energy sources. And in the end, of course, it also depends on factors such as usage behavior.

Thank you very much for the interview!