Clean-up experiment unsuccessful
An experiment carried out in Brussels’ Leopold-II tunnel to test a new way of cleaning pollutants from the air has been declared a “waste of money” by a Flemish expert, after the experiment terminated having produced no usable results.
Ultraviolet light has little effect on pollutant particles in Brussels’ tunnels
The test (Flanders Today, 30 January) was run by the European research consortium PhotoPAQ, and involved a process called photocatalysis, in which particles of titanium dioxide (TiO2) embedded in cement applied to the walls along a 160-metre section of the tunnel were bathed in ultraviolet light. That caused the TiO2 to react with pollutants, mainly nitrous oxide, making it relatively harmless.
As explained at the time by Dr Anne Beeldens of the Belgian Road Research Centre, which was monitoring the experiment, part of the goal was to find the optimum level of UV required, as the UV lamps could partially replace the current ventilation system in the tunnel, reducing energy costs.
A previous experiment in the same spot in 2011, over a shorter distance, proved inconclusive, partly because the UV intensity was not high enough. For the latest experiment, the UV was stronger, the cement was applied more uniformly, and the length of the test section was doubled.
But it was not enough. “The UV component of sunlight in these parts is strong enough, but it proved to be extremely difficult to achieve the same intensity with UV lamps,” Beeldens explained. “Also, the humidity of the air in the tunnel was very high, which also reduces the effectiveness of the product.”
According to Frans Fierens, an air quality expert with the Flemish Environment Agency, the experiment was “an unfortunate waste of money”. He told De Morgen that the process using TiO2 has only ever worked in the laboratory, never in a real situation. Above all, he said, the experiment was approaching the problem from the wrong angle.
“The essence of air quality policy should be to avoid air pollution, not to allow the air to be polluted and then try to clean it up,” he said. “The last part is in any case impossible.” The most effective measure, according to Fierens, would be to reduce the volume of traffic. “That may not be the most popular measure, but it is the most efficient.”
The experiment was budgeted at €100,000 back in January; the actual costs are not known. The entirety of the financing was provided by the Lyon-based PhotoPAQ.
