From bicycle bridge to fertiliser

The province of Friesland in the Netherlands is currently building the world’s first movable bicycle bridge made of biocomposite. If everything goes according to plan, the bridge will be turned into fertiliser in 100 years.

The bridge is located near the village Ritsumasyl and spans the Van Harinxma channel. It replaces an old bridge that has reached the end of its lifespan. The new bridge is asymmetrical, can be opened and has a biocomposite deck.

The bridge is the first of its kind. It has to be strong enough to carry cyclists and the occasional car. To find the right composite, specialist company Delft Infra Composite selected six different kinds of resin and the same amount of fibres. These were mixed and tested until the right mixture was found. Flax fibres, a waste material of the flax seed industry, performed best, combined with a resin with a high bio content. Unfortunately, no fully biobased resins are available yet. The bridge will consist of 80 per cent biobased materials.

To test the performance, the movable section of the bridge, which rests on a concrete pillar, was constructed on a scale of 1 to 3. Researchers at Technical University Delft simulated the opening and closing of the bridge a million times. The aim was to be able to use the bridge for 50 years, but the test showed that the material could be used for more than 100 years. Once the bridge has served its use, it would ideally be used as fertiliser.

When the test bridge, which might be used as a pedestrian bridge, had been proved durable, the actual bridge deck, measuring 66 by 4 metres, was constructed. It consists of a bottom sheet of biocomposite to which 1.2 metre high biocomposite I-profiles are attached. The top sheet is also made of biocomposite.

Compared to the previous concrete bridge, the new one is feather light. The construction weighs 30 tonnes, compared to 400 tonnes if it would have been made of concrete.

The bridge is planned to be opened in October 2019.

The project, called DRIVE, is the second biobased bridge in the Netherlands. In 2016, the Technical University Eindhoven created a biobased pedestrian bridge (read more about this project here).

Renderings: DRIVE