People in cities can grow enough of lettuce, beans and tomatoes for consumption by utilising roof tops of the building they stay in. “In our inFarming project - which is short for ‘integrated farming’ - we are developing solutions that can be speedily implemented for the urban landscape. Our goal is to grow vegetables atop existing buildings,” says project manager Volkmar Keuter at the Fraunhofer Institute UMSICHT, Germany. The benefits: reducing the area required for agriculture, almost no transportation costs and, as a result, lower emissions - not to mention more freshness when the tomatoes grow on the roof top, says Keuter. Water consumption is minimal, too: in a self-contained system, water used for the plants is circulated back, cleaned and reused. Multifunctional microsieves and photocatalytic and thus self-cleaning coatings keep the water quality high, according to a Fraunhofer statement. Nutrients for the plants can even be filtered out of rainwater and waste water. “Our concept relies on hydroponic systems or hydrocultures. A thin, controlled film of water is all it takes for plants to absorb needed nutrients,” says Keuter. “The advantage: the yield is 10 times higher, and soil is too heavy for many building roofs. That is why we are working on systems to supply plants with nutrients,” Keuter adds. There are around 1,200 million square metres’ worth of flat-roofed, non-residential buildings in Germany alone. Roughly a quarter of this area could provide herbs and vegetables with a place to thrive.