If you wander down the picturesque streets of the old town of Krakow, Poland, in winter, you may encounter a heady scent. In 2021, the city authorities adopted a novel approach to managing icy roads and paths, replacing the salt usually scattered by park attendants with spent coffee grounds donated by local cafes.
The aromatic substance is an attempt to tackle a growing concern: the grit we cover our roads in every winter is increasingly wreaking havoc on the environment. In particular, it messes with freshwater ecosystems that are already among the most imperiled on Earth. “It is quite possible in the next 50 years, given current trends, that a lot of freshwater ecosystems could be salinised to the point of pretty severe ecological impact,” says Bill Hintz, a freshwater ecologist at the University of Toledo in Ohio.
Why is there salt in road grit?
Every winter across the globe, we chuck tens of millions of metric tonnes of salt onto our roads to lower the melting point of ice and keep them navigable for drivers. They provide entertainment, too. In Scotland, the fleet of 230 gritters are given funny names by the public: things like Snowcially Distanced, Grittney Spears and Yes Sir, Ice Can Boogie.
But what is increasingly apparent is the extent to which road salt is running off into precious freshwater ecosystems, putting biodiversity at risk and threatening drinking water…