Farming in town – that’s how the world’s great cities seem to be coping with the future. The advantages are plain: fresh produce with a significantly lower carbon footprint.

Remember Manhattan’s rooftop vegetable garden and Hackney City Farm in London? The latest example of urban farming comes from Berlin, where an even more revolutionary self production system will come alive as soon as 2013.

The project is called Frisch vom Dach (literally “fresh from the roof”) and it’s based on a system for sustainable food production known as “aquaponics“, which consists in raising aquatic animals and cultivating plants in a symbiotic environment.
In other words, the fish excretions are converted into fertilizer for the plants, which in turn purify the water for the fish.

Although it sounds like science fiction, the water-based aquaponic concept was invented in the 1970s – but the Fresh from the Roof project, hosted on the roof of a former malt factory in Berlin’s Schöneberg, will be the first to use it on a large scale. The result will be a huge production of fresh fish and zero-mile vegetables for all Berliners, to be sold partly on site and partly by local retail markets.

The three founders are planning to create a 7,000-square-meter roof garden to harvest lettuce, herbs and tomatoes, as well as raising different species of fish inside the old factory’s containers.

And since just 200 liters of water are required to produce one kilo of fish (compared with  some 15,500 liters required for producing one kilo of beef), Frisch vom Dach appears to be more than just a urban project – it could be set up anywhere, even in places with water shortages.