The Frisch vom Dach, or Fresh from the Roof project, plans to create a 7,000-square-meter (1.73 acre) roof garden, complete with a fish farm, to provide Berliners with sustainable, locally-grown food. They hope to sow the seeds of a new form of urban agriculture, arguing that traditional farming needs to evolve — and soon.
In 2013 they plan to harvest lettuce, herbs and tomatoes, as well as raising different species of fish from the roof of a former malt factory in Berlin’s Schöneberg district. Once their unorthodox farm is established, they expect to produce tons of vegetables and fish each month.
Key to their plans are a row of massive vats near the top of the rambling factory. Formerly used to dry barley, they want to repurpose the containers as a fish farm.
The fish will be sold as food and, crucially, their excretions, especially the ammonia excreted through the gills, will be converted into nitrates. That will serve as fertilizer for the plants growing in green houses above the fish tanks. In turn, the plants will purify the water for the fish. The system for sustainable food production is known as “aquaponics.”
“The beauty of the system is that you just need to add fish food,” explained co-founder Karoline vom Böckel, who specialises in strategy and research.
A small-scale prototype of their vision has boosted their optimism. In a double-decker metal structure built out of an upcycled container, they are already raising fish on the lower level and growing tomatoes and lettuce in hydroponic beds above.
Part of the system’s appeal is the flexibility of the symbiotic arrangement. Meanwhile, it uses water sparingly. Just 200 liters of water are required to produce one kilo of fish, the group says, far below the average 1,000 liters used in conventional fish farms. Producing one kilo of beef requires some 15,500 liters of water, they estimate.
“This farm is not just an urban project. It could be set up anywhere — even in places with water shortages,” Leschke said. An estimated €5 million ($6.7 million) will be needed to set up the scheme, and the Fresh from the Roof team are still on the lookout for potential investors.