Belgian railroad network manager Infrabel is conducting tests using liquid nitrogen and electricity, among other things, to control weeds in and along the tracks. It does so with its Dutch counterpart, ProRail, and the international railroad organization UIC.
Both rail network managers are looking for new methods to control weeds on the tracks, although the tests with liquid nitrogen raise questions about their environmental friendliness.
The tests are part of ‘Life-Nature-Rail’, a project led by ProRail that studies alternatives to chemical weed control. The project has a budget of 1.6 million euros and is co-financed by the European Life program. The techniques are tested on safety tracks and service paths beside rail lines.
Three new techniques were tested
In the electrical treatment of weeds, plants are electrocuted, so to speak, causing irreparable damage to the cells and the plant to die. In cold therapy with liquid nitrogen, or cryogenic treatment, a small amount is sprayed directly on the weeds. The contact with the nitrogen will freeze and kill the weeds.
The possibilities of slow-growing grass in combination with a mowing robot are also being investigated, an alternative that seems more environmentally friendly than liquid nitrogen or the chemical glyphosate that Infrabel currently uses to keep the 6,500 kilometers of main tracks weed-free.
Liquid nitrogen can be environmentally friendly for weed control in a small-scale, targeted application. Unlike chemical herbicides, liquid nitrogen does not leave harmful substances in the soil or groundwater.
It evaporates and returns to the atmosphere as nitrogen gas, from which it was originally extracted. In that sense, it also does not increase nitrogen deposition covered by environmental standards.
However, making liquid nitrogen requires a lot of energy, which can cause CO2 emissions, depending on the energy source. The intense cold of -196°C also allows the product to kill local soil life, such as bacteria, fungi, and worms.
Spray train
To keep the main tracks weed-free, Infrabel engages a spray train that runs twice a year. Infrabel receives derogations to the pesticide ban from regional authorities for this purpose.
These derogations “remain necessary to limit the number of interventions in the tracks and thus also to limit the impact on the regularity of the trains,” Infrabel says. “Indeed, the alternative techniques cannot yet be structurally applied on a large scale.”
On some 2,500 km of sidings and part of the service paths in the main tracks, the rail network manager uses as many alternative methods as possible, such as mowing, weeding, and grubbing.
The Swiss railroad company SBB deploys a specially developed hot water train to control weeds. Infrabel has also developed a similar hot water train in the past, but although initial tests have been encouraging, the train is not currently operational.
In 2023, Infrabel said it wanted to refine the concept further first and was looking at ways to make water and energy consumption more sustainable.
Track weeds must be controlled because they pose a problem for train traffic safety. They can affect the stability of the ballast—the stones under and between the tracks—or reduce the visibility of signals.
