A clean slate – this stone has what it takes

STEAG innovation not only provides healthier air in cities, but also is grabbing attention from around the world

Some parts of our surroundings are so much a part of our everyday lives that we hardly notice them any more. But it is worth your while to take a closer look – down at the street, for example. It could just be simple pavement, of course. But it might also be Photoment, a cement mixture made from black coal fly ash and white pigment that removes nitrogen oxides (NOx) from the air.

STEAG Power Minerals GmbH, with its headquarters in Dinslaken, developed the innovative construction material – which is meant to neutralise the emissions from diesel vehicles, for example – and advertises with the slogan: ‘Das kann kein Baum.’ (‘No tree can do that.’) Indeed: ‘A small paving stone cleans one cubic meter of air,’ explains STEAG project manager Dennis Pannen. ‘In many cases, there are no known solutions for nitrogen oxide reduction outside of bans on driving,’ adds Sarah Höfer, head of marketing and communication. ‘Of course, we cannot solve the entire problem with Photoment alone, but it allows us to at least make an important contribution to improving the urban climate.’

No light, no rain, no go

The removal of harmful substances is carried out through a photocatalytic process, which means the material needs daylight or artificial lighting to pull nitrogen oxides from the air, and rainwater to turn them into nitrates. Admittedly, that doesn’t exactly sound environmentally friendly. ‘But the nitrates are created in such small amounts during this process that it is inconsequential,’ according to Dennis Pannen. In the STEAG Power Minerals laboratory, amongst dozens of bottles, hoses, glass cases and test tubes, various temperatures, light intensities and types of precipitation are simulated. But the stone material stands in the spotlight. The tests are determining the most effective mixture of its individual components.

Improving the quality of life in the Metropolis Ruhr as well as internationally

In Bottrop alone, also known as ‘Innovation City’, some 50,000 Photoment pavers have been installed on a surface area of 750 square metres. This has reduced the levels of nitrogen oxides by an average of 12 percent. There, at a busy intersection, is where we are set to meet up with Jan Küppers, project manager at Innovation City Management GmbH. When asked about where the Photoment has been laid, his quick response is: ‘You’re standing on it.’ Aha. We see ... nothing. Except simple paving stones. But what we do notice is that the stones that keep the air clean are clean themselves: no spots, no moss – they look as good as new. ‘Yes, they clean themselves – a nice little side effect,’ says Küppers, knowingly. Also interesting for private individuals is that the construction material can be used in all types of cement work – roof tiles, facade paints or noise protection walls. For this reason, paving stones with Photoment have now become a part of the product range in select DIY stores.

Interest from all around

More and more city planners in Germany are coming to rely on the special pavers, in addition to sustainable city design with less traffic and the expansion of green spaces. The Metropolis Ruhr is getting things started – which means a home match for power station company STEAG with its headquarters in Essen. But other economic centres such as Stuttgart are helping lead the way. Photoment is also gaining international attention – a delegation from China recently visited the STEAG Power Minerals laboratory to meet with the experts on-site.

The innovation is not only clean, but it is also an award-winning idea according to the jury of Europe’s largest independent environmental and economic awards. They distinguished Photoment with the renowned GreenTec Award in 2016 in the category of urbanisation because of its ability to improve the quality of life in cities.