Harmful contaminants accumulate in the gravel used for sanding the icy roads in Finland, particularly when it is used on asphalt.
If contaminant limit values are exceeded, the gravel becomes hazardous waste and cannot be reused.
Spring is marked each year in Finland with legions of mechanical street sweepers combing the roads and paths to sweep up layers of anti-skid sand and gravel laid through the winter to add traction and grip. The crushed granite can’t be used again the next winter, however, if it has absorbed too much foreign matter from passing traffic and the elements.
Oil-based hydrocarbons that seep into the gravel from the asphalt and car exhaust pose the largest threat. If the contaminant saturation exceeds certain limits, the swept-up gravel must be classified as problem waste and disposed of accordingly. This is why Finns tend to use salt on most major motorways that host a lot of traffic.
“It doesn’t make any sense that it is more efficient to buy new gravel than recycle the old stuff. First, we mine the granite, then we spread it on the streets as an anti-skid treatment, and then when it is cleaned from the streets at the end of the season, it is unusable because it is hazardous waste. It is a natural resource, after all,” says Mikko Kunttu of the Kuntec municipal engineering arm of the southwest Turku region.
Kunttu says the residue from engine exhaust was still found in sand used for de-icing years ago, but this should no longer be a problem due to auto industry advances.
“If we were to collect the gravel in the spring, store it and spread it again the following year, the structure would break down and become finer, which would mean it would create much more dust,” says Kunttu.
Finland has made a concentrated effort to use gravel as opposed to sand for years to cut back on hazardous dust levels in the spring. Several student theses have been written on how the material could possibly be reused. In Denmark, for example, the anti-skid gravel is used as aggregate in the making of concrete.
Gravel aggregate that is unsuitable for recycled use is used to support structures and the like at landfills, a time-consuming and expensive alternative that also requires a separate environmental permit.
In practice, a large percentage of the gravel spread over roads and streets in Finland is fresh from production.
“It would be of benefit to everyone, of course, that the majority could be recycled somehow and put back into use,” says Kunttu.
Related stories from around the North:
Greenland: Study finds increase in litter on Arctic seafloor, Blog by Mia Bennett
Sweden: Sweden tackles plastic bag problem, Radio Sweden
Russia: Submariners feed polar bears with garbage, Barents Observer
United States: Chemical contaminants suspect in mystery of Alaska chickadee beak deformities, Alaska Dispatch