Recycling in construction: rubble is not waste, but a raw material

Mr. Imhäuser, the Hesse-Thuringia building industry association is calling for the recycling rate for building materials to be increased in order to save energy and resources. Surely you can only support that?

Absolutely. We are a company that focuses on the circular economy with mineral substances. But the impetus to keep these raw materials in the value cycle must come from politics and of course from the builders. Architectural offices also play a decisive role here. They could encourage the decision to recycle more with the way they plan.

What materials and quantities are we talking about exactly?

The main sources of mineral waste or raw materials – the term is a matter of perspective – are civil engineering for buildings, roads and railways and of course building construction, most of which are excavated earth and rubble. And very, very much: This construction waste forms the largest and heaviest flow of raw materials in Germany. Every third truck on our roads transports bulk goods, i.e. mostly mineral raw materials.

According to the association, a growing proportion of these loads are sent to landfills. It is also common to use masses of earth and rubble for road construction or for the recultivation of opencast mines. That’s probably not the cycle you’re imagining?

No, backfilling counts as recycling, but just backfilling rubble does not do justice to its raw material potential. It would be better for the economy if, for example, the concrete were used again in building construction, so the added value remained high.

Can you turn concrete into concrete again?

Concrete aggregates can be obtained as alternatives to sand and gravel. We are planning a large-scale plant in Frankfurt’s Osthafen, in which rubble will be broken up, washed and even sorted into an aggregate by color. And that where the rubble accumulates and the concrete is later used again. For the climate balance of buildings, it is essential to include the transport routes of the mineral raw materials, because gravel and sand are often transported over hundreds of kilometers. This makes transport more expensive than the load and is of course not resource-saving.

So the technical possibilities for the recycling of building materials are there. Where is the problem then?

Everyone involved, from the client to the approval authority to our company, has to overcome disproportionately high hurdles because the legal requirements are deficient. It’s always about environmental hygiene, economy and of course structural engineering issues. All three are justified, but the effort is so great that there is no incentive to use the potential of the raw materials in depth. Unfortunately, the ordinance planned for 2023, which is intended to regulate the recycling of mineral waste in road construction and civil engineering, will not change that much.

The ordinance promises uniform rules nationwide. Each federal state still has its own specifications, such as whether excavated earth or used track ballast can be reused or whether it should go to the landfill as waste?

Yes, there are big differences. However, the new regulation provides for an opening clause, so that the chance of a finally uniform regulation will probably be missed. What we also need would be a clear definition of the stage of processing after which these mineral substances are no longer considered waste, but can be treated like normal building materials. That would make a lot of things easier.

What are the regulations in Hesse, how far have we got with recycling?

Hesse has a lot of catching up to do. My suggestion would be to define a minimum recyclate quota, whereby the public sector, as the largest builder, should commit itself to a higher proportion and, when awarding contracts, should give preference to providers who recycle a lot of material and only need short transport routes for this. Querying this should be standard. Such an approach would have an enormous promotional effect and would be a real incentive to look for ecological and economical ways of recycling.