Dutch bridge constructed using hemp as building material

While plenty of cannabis goes up in smoke in coffee shops around the Netherlands, Dutch researchers have found a new use for it - as an environmentally friendly building material to rival cement or steel.

They have used hemp - a variety of cannabis which has many industrial applications including in textiles and insulation - and flax - the plant that linen is made of - to make an experimental footbridge to test the materials' load-bearing properties.

"Actually it's the first 'bio-based' bridge in the world, as far as we know," said Rijk Blok, an assistant professor of structural design at the Eindhoven University of Technology.

The hemp and flax fibres are combined in a resin that is stuck to a core made of polylactic acid, a polymer also made of plant material, to form the span of the 14-metre (46-foot) bridge over a stream on the university campus.

The developers - at several Dutch colleges and companies - are using sensors to monitor the bridge's performance as people walk and run over it for a year.

They first had to demonstrate that the bridge could withstand a load of 500 kilograms per square metre in laboratory stress tests before building permission was granted.

"This was our research - trying to find out: Can they be used in a structural load-bearing capacity? And this bridge is the proof," Blok said.