Strange green pipes above a European highway aren't there for decoration: They hold algae that is gobbling up excess carbon dioxide expelled from cars as part of an environmental project.

Image source: Vimeo

The pipe system, through which the algae flows, was designed and installed for a garden festival in Geneva by the group called The Cloud Collective. It was one of 13 gardens selected earlier this summer to be constructed.

The group described the "viaduct" as "quite out-of-tune" with what one would typically imagine of a garden. The Cloud Collective instead sought to "try to prove that even these locations of highways and car dealers – despite their anonymous and generic character – can play an important role in the production of food and biomass."

Image source: Vimeo

Here's how it all works works:

A closed system of transparent tubes, clinging onto the viaduct is used for the production of algae, which grow on sunlight and CO2, both abundantly present on the site. These algae can be as combustible biomass or as raw material for different cosmetic and alimentary products. A steel structure, supporting all the secondary equipment such as pumps and filters, functions as a marker for the quickly passing traffic and provides explanations on a more detailed level for pedestrians and cyclists. The functioning and the placement of this bioreactor signals practices of the future: food production in an urban environment, the conservation of green space and the reinterpretation of existing infrastructures.

Watch this video about the innovative system:

(H/T: Science Alert)