Humans of TU Delft: Mauro Overend is adding value to recycled and reused glass

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“My research is focused on sustainable materials and low-carbon structures, so how to use materials and structural design effectively to construct buildings that are more efficient in their use of materials. Specifically, it’s about the environmental impact of the materials that we are using. The way most construction materials are produced also requires a lot of energy so we must be careful which types of materials we are using and how much of them we use.

Essentially, we need to design efficient structures that use lower carbon materials rather than inefficient structures that use high carbon materials. And it’s not only about new buildings, but how we reuse existing buildings, whether we reuse the entire building or harvest materials from them. And then, it’s about how to reuse those harvested materials. There is an enormous amount of construction and demolition waste. It’s by far the largest amount of waste we produce as humans. In volume, it is larger than all other industries put together.

‘The materials are a resource’

So, how do we deal with all this construction and demolition waste? Many people see it as a problem, but I think we ought to start looking at it more as an opportunity. The materials are a resource, an unusual stream of materials coming from existing buildings and construction demolition waste. How can we use those materials rather than always relying on the raw materials that we get by extracting new materials from our planet?

TU Delft is a leader in glass research and education – glass structures, glass engineering, and glass architecture. We are building on that with the UPCAST GLASS project, which is about how we can recycle waste glass into high value products. Most people think that a lot of glass is already recycled. But with glass, there is a very clear distinction between container glass – essentially bottles – and the flat glass industry, and these two are quite separate. The production methods are different. The raw material, at least the basic material, is not dissimilar but somebody who produces bottles is not producing flat glass for buildings.

There is a very good collection and recycling rate for bottles. It varies from country to country, but here in the Netherlands it is in the order of 80%. A lot of the bottles are in fact recycled, they are collected and crushed and then remelted into new bottles. Some are actually reused, which is even better. They are collected, washed, and reused, which is perhaps the ideal option. The bottle industry is doing well.

The flat glass industry is not doing so well and this is the case everywhere. With flat glass, which is glass from windows in buildings or cars or glass in display screens like TVs or mobile phones, nearly none of it gets recycled. Some objects, like steel window frames or the components in electronic devices, are valuable and get recycled, but then you’re left with a piece of glass. And most of that glass is taken to a landfill, or at best it gets crushed into fine dust or small particles that is sometimes used in concrete or road surfacing materials. That is better than nothing, but the value of the crushed material is very low compared to the value of the original product. So we are recycling a small amount of it, but most of it is what is known as down-cycling, going several steps down the value chain.

‘It won’t be used to produce another transparent window’

One of the main reasons that flat glass is not recycled is because generally most of it has some coatings, polymers or other materials that are used in the construction of the glass window frame systems or glass display screens. These coatings are essentially like foreign materials. If the glass is removed with these contaminants and put into a flat glass production line, those contaminants will find their way into the glass production. That will contaminate the whole glass production so that you end up with a glass window or a glass screen which has imperfections. At this stage, these imperfections are not deemed acceptable for consumers or the glass industry in general. So many glass producers are very wary of introducing anything in their raw materials that contains any of these impurities or imperfections.

So we have a situation where there is a lot of glass at the end of its life when buildings are demolished or when consumer electronics come to the end of their life with no use. Following up on the findings of the Re³ Glass project, UPCAST GLASS aims to find ways in which this so-called contaminated glass or imperfect glass from existing products can be recycled into high value products. We are not putting the glass into what is known as the float line, which is the line that produces these flat glass products because that is very sensitive to imperfections, but we are instead using a casting process. The glass is melted in a furnace and can then be cast and shaped into other things. It won’t be used to produce another transparent window, but it can be used to produce a high-performance brick, or a visually attractive cladding panel, essentially something that can be used for another purpose which is of higher value than crushed glass that goes into paving materials.

We received an NWO (Dutch Research Council) grant to fund this four-year project and we will be testing and assessing the mechanical performance of these new glass components. People who might want to use this glass will want to know about the strength and other important properties that effect the performance. At the end of the four years our aspiration is to have a database of different glass waste streams. If the glass waste comes from the consumer electronic market or the window glazing market, each will have slightly different coatings and contaminants. So we will try to classify these waste streams and then each waste stream can produce a certain type of glass with a predictable appearance and performance. In the end, we hope to map out the major waste streams with their contaminants and to link that to the type of performance you could achieve. I think that would create the most useful set of information for developing products, and create a big database that others can use in the future to develop whatever beautiful, high-performance and high-value products they wish to develop.”

• UPCAST GLASS: Upcycling waste glass by casting, is a project by Dr Mauro Overend, Dr Faidra Oikonomopoulou and Dr Telesilla Bristogianni, from the Architectual Engineering +Technology Department, Faculty of Architecture and the Built Environment at TU Delft. The project will run for four years and will be supported by the TU Delft Glass Research Group, Vlakglasrecycling Nederland, Maltha Glass Recycling, Corning and EOC Engineers.

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Heather Montague / Freelance writer