By recycling the stone powder, the natural stone sector can earn additional points in its life cycle assessments and EPDs

 At the exit of the gang saw, all the volume that was once stone between the slabs has become stone flour.

As part of the “Marmomac Meets Academies“ presentation at the Verona trade fair, Professor Giuseppe Fallacara from the Politecnico in Bari raised the topic

In a separate article from our “Stone Insight“ series, we provide an overview of the data in an EPD and how it is sorted: https://www.stone-ideas.com/103846/life-cycle-assessment-of-a-building-four-categories/.
 

Giuseppe Fallacara, professor at the Politecnico in Bari in the south of Italy, usually deals with modern concepts of how to use natural stone in architecture. At Marmomac 2023, however, in the presentation “Marmomac Meets Academies“ in Hall 10, he showed examples of what can be made from stone powder using 3D printing. It is produced in large quantities when the raw blocks are cut into slabs, for example.

Fallacara is always friendly and cheerful and is good at explaining things, so we asked him why he attaches so much importance to recycling stone powder.

And with his answer, he gave us a bit of a wake-up call: if the stone powder does not remain as waste but is used in new products, natural stone can improve its already very good ecological balance even further.

Let us go into more detail: we are talking about Environmental Product Declarations (EPD).

Although these collections of data on the environmental aspects of a building are not yet mandatory, they will become so in the foreseeable future. The pioneer in the USA is the state of California, where CO2 limits have been in force for certain buildings since August 2023.

Progressive architecture firms are already demanding EPDs for the building materials they use. Behind this is the desire of their clients and investors to obtain buildings with certifications (e.g., LEED, BREEAM), as these are easier to rent or sell.

In our expert discussion with Sarah Gregg from the Natural Stone Institute (NSI), she predicted this development and drew the industry’s attention to its importance: “Getting EPDs done now will position natural stone to thrive as a low-embodied carbon solution.“

“Cradle-to-Crave“

“Cradle-to-Crave“ describes the approach of the current EPDs. This means that all environmental aspects of a building are included in an EPD, i.e., from the production of the building materials to the operation of the building, its demolition and the recycling of the building materials.

Previously, the approach was only “cradle-to-gate,“ i.e., from production to the construction site.

For the stone sector, “cradle-to-crave“ means, as we learned from Professor Fallacara, that a life cycle assessment now also takes into account what happens to the stone powder from sawing the raw blocks, among other things.

And particularly important is: if it is recycled, this can be positively included in the balance.

Exact figures on how much stone powder is produced worldwide during the further processing of the raw blocks are not available.

HHowever, it is possible to visualize the dimensions: at the exit of the gang saw, all the volume that was once stone between the slabs has become stone flour.

You can also get an idea of the volume from the figures in Dr. Carlo Montani’s statistics yearbook “Rapporto marmo e pietre nel mundo / Report marble and stones in the world.“ Let us take the 2021 edition as an example: at that time, 318 million tons of stone were extracted from quarries worldwide, which after many steps had finally become 91.5 million tons of products.

Parts of this huge difference were blocks or slabs that could not be used due to cracks, or offcuts, and also stone powder.

It is interesting to note that over the past two decades, Montani has been admonishing the sector to recycle this waste.

And indeed, there have been many experiments in companies and research at universities on the subject. Many of them resulted in feasible uses, but mostly failed due to the costs: stone powder as an aggregate for ceramics, for example, was usually not worthwhile because clay was cheaper.

Now the guiding principle is the circular economy, and the aim is to reuse waste instead of natural resources wherever possible.

The previous burden for the stone sector could even become a pleasure or a joy: natural stone companies that have established their own artificial stones on the market are already in a doubly good position. This is because these companies can practice the circular economy within their company. E.g.: German Hofmann Naturstein has developed a clinker brick which contains 40% stone powder.

Montani had already thought along these lines: when presenting his statistics yearbook for 2019, he suggested that instead of competing with artificial stone, we should think about synergies with the man-made material.

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(11.12.2023, USA: 12.11.2023)