Its door handles are made of salt. Its walls are made of sunflowers. Its furniture is made of Japanese knotweed. And it was stained with dyes made from filtered urine. Is this recycling marvel in southern France the future of architecture?

In a former railway repair shop in the southern French city of Arles, flasks of lurid green algae are bubbling away on a shelf, in a room that looks like a cross between a modern-day laboratory and a witch’s potion-brewing den. Nearby, a 3D printer spews out curious objects made from algae-based bioplastic, while samples of algae-dyed textiles hang on a rack. Some of the walls appear to be made of rice cakes, others look like Weetabix, while some are daubed with a coat of porridgy gloop. All are natural byproducts of the local sunflower industry, the mashed-up pith and fibres redeployed as acoustic insulation. Elsewhere, there are antibacterial door handles made of salt, harvested from the region’s salt marshes; thermal insulation made from bales of local rice straw; and bathroom tiles made of waste clay from a nearby quarry.