“There are many ways to make glass more sustainable”

It is infinitely malleable and therefore offers all kinds of possibilities for designing packaging. It’s also practically infinitely recyclable because it can be melted down again and again without compromising quality. Glass is practically inert, so it hardly reacts chemically: It neither releases substances nor changes itself.

This inertness is a top priority for the food industry and the pharmaceutical sector. Glass is also gas-tight. This is important for medicines, but that’s not all. If you leave a plastic mineral water bottle in the car in the sun, for example, it swells and carbon dioxide escapes.

Nevertheless, there is competition from other forms of packaging such as plastic, cans, and drink cartons. They outperform glass, especially in terms of weight.

That’s right. Plastic bottles, for example, are actually lighter and cause less carbon dioxide emissions during transportation. But plastic can’t be recycled at will. I can’t easily make a new product from a batch of 100% recycled plastic, because the molecular chains have become shorter. I need new polymers every time, and most of them are made from crude oil. Plastic also has the disadvantage that substances can migrate from the plastic into the product and change the taste, for example. In the EU, many plastic additives are subject to strict limits that are regularly reviewed. Glass therefore comes into its own with sensitive foods, because it is practically inert. 

And what can be done about the weight?

Thin walls really are a major topic. They save raw materials and energy during production and make the packaging lighter—which in turn saves fuel during transport. Thin walls are of particular interest for disposable containers, which are often transported over long distances. Forty-eight percent of all glass containers in Germany are disposable, so saving material is an effective lever. Glass has already become thinner over the decades, thanks to new technical processes. In addition, the wall thickness has become more and more uniform. But we’re still a long way from the end. In the meantime, reusable beer bottles that are significantly lighter than conventional ones have also been introduced.

What other measures can be taken to make glass even more sustainable?

Increasing recycling rates even further—not just in Germany and Europe, but worldwide. Germany, Austria, and the Netherlands were the first to establish glass recycling in the 1970s. In Germany today, more than 80 percent of glass is recycled rather than thrown away. In the meantime, however, other countries such as Switzerland, Norway, and Sweden have overtaken us. It’s also good to know that other countries have caught up massively. Hardly any recycling used to take place in Spain or Italy. Today, these nations are also reaching high values—unlike the United States, where the figure is less than 30 percent. There, but also here in Germany, it’s important to continue encouraging people to dispose of used glass correctly.

Recycling is one thing. But can you still tease something out of the material itself?

Of course, through further energy savings in production or through alternative sources of raw materials. Glass is made from the primary raw materials sand and soda—i.e. silicon dioxide and sodium carbonate—as well as dolomite or lime—magnesium or calcium carbonate. It has a relatively high CO2 load due to the carbonates. In the future, lime could alternatively be separated from drinking water, for example, in order to conserve other lime deposits. The salt obtained in seawater desalination plants could be converted into soda. This sodium chloride could be broken down into its components via electrolysis—the sodium could then be used with water and CO2 from industry for soda production, and the chlorine could be used to disinfect drinking water.

Clearly yes, it must. This is because the entire industry in Europe is under massive pressure as a result of trading in CO2 certificates. I see a multi-stage process here. We need to recycle more and use CO2-neutral raw materials. We have to reduce weight and also work on the coating of the glass surface in order to optimize the whole thing. There are also alternative energy sources—wind, solar, and hydropower. Then we can actually melt glass in the future without natural gas or oil. Whether we use the electricity directly or turn it into hydrogen first remains to be seen. Incidentally, the idea of using electricity is nothing new—it has been done this way for many decades. Glass is melted in furnaces that are normally heated from above with gas. For dark glass, I also have to use electrodes to supply radiant heat from below, because I can’t get enough energy into the area at the bottom of the tub via the tub vault alone. The key factors are that the electricity is affordable and comes from renewable sources.

What opportunities do you see for glass in the future?

The use of this material will increase massively—in very different areas. In the future, specially equipped window panes will produce electricity. Buildings can also be heated by radiant heat, as in a conservatory. In general, glass will continue to gain importance in insulation, house construction, and building technology. Because we are now able to produce increasingly thinner glass, we can also save a lot of material. The automotive industry is tending to go back to glass for certain plastic parts, such as lenses for LED headlights, because of the high quality. And then there’s even the idea of storing data in glass, in huge quantities. For the food sector, I expect to see a return to glass in some areas because of its unique properties.