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So is there such a thing as infinite recyclability? Yes. But it's not that simple! Because retaining the initial properties of the product demands sophisticated technical expertise. Take glass, for example. In theory, this material can be melted in a furnace an infinite number of times without altering its performance... As long as you don’t mix all types of glass together. “The flat glass used in buildings and vehicles must retain its excellent transparency”, explains Xavier Meyer, VP for the Circular Economy at Saint-Gobain. “So you can’t mix it with colored glass (bottles) or glass containing boron (glass wool) or lead (crystal), because windows and windshields must not contain any contaminants”.
This is the essential difficulty of infinite recycling: it must never alter the end quality of the new product. And this applies to all the materials we think of as being recyclable forever, including gypsum and metals. For example, cast-iron underground pipes can easily be melted in an industrial furnace. Until the 1950s, these pipes were made of gray cast iron. This material was then replaced by ductile cast iron, which gives them exceptional properties in terms of mechanical strength and flexion. So the older pipes can therefore never be recycled into ductile cast iron. On the other hand, they can be reused to make pipes for homes, which did not have to meet the same specification.
So suitability for infinite recycling is governed by a series of factors: product composition, level of contamination and the ability of the industrial process to transform waste into a secondary raw material identical to the raw material straight from the quarry. But again, it's not that simple! The example of gypsum and plasterboard is quite instructive. Plasterboard has paper coating on both sides, which must be removed. But in reality, some paper residue is always left behind, and good quality raw material must be re-injected into the manufacturing process.
So to be infinitely recyclable, each product requires specific processes spanning every stage from collection and transportation to sorting, decontamination and reprocessing. Their complexity depends on the products to be recycled. But the effort is worth it from the environmental perspective. Infinitely recycling a product conserves the raw material. This closed-loop process then makes a valuable contribution to sustainable resource management, biodiversity conservation (no landfill) and CO2 reduction. But does that make it profitable?
For an industrial group like Saint-Gobain, offering such a solution sets its offering distinctively apart in the market, as well as adding real value for customers wanting to contribute to the circular economy. For the end-user consumer, it holds out the promise of buying a sustainable and responsible product that addresses environmental challenges. “There’s a real need for a circular economy across all sectors of the economy,” continues Xavier Meyer. “The increasing scarcity of resources and tighter regulation of landfill will push industrial companies to find solutions around new recycling services.” That said, the more complex the recycling process, the more expensive it is. And the parameters of waste sorting, reprocessing or collection can sometimes tip the scales heavily.
In the near future, developments in industrial processes are likely to converge with sustainable product design, making it possible to extend the list of infinitely recyclable materials. Recently, the PET plastic used in food packaging has been the focus of scientific developments using an enzyme that separates monomers that can then be used to manufacture new PET bottles. Saint-Gobain has developed a new industrial process for treating used chromium-based refractories from some of its furnaces. This new technique enables toxic chromium (chromium 6) to be converted to chromium 3... And therefore refractories to be recycled.
The Group is now focusing on developing new solutions to recycle consumables such as abrasive wheels, and is contributing to the development of recycling channels for a range of marketed construction materials.
Faced with the increasing scarcity of natural resources, infinite recycling seems to provide a relevant solution in terms of sustainable development and biodiversity conservation. But there is still a need to improve industrial processes in ways that increase the recycling rate of end-of-life waste and facilitate its reprocessing...
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