From Changing City Updates blog

The system, which has been trialed in the UK, is claimed to produce 20 times the yield of field crops, using a fraction of the space and 92 percent less water. 

This isn’t our usual development proposal update – 635 Richards is a parkade, owned by the City of Vancouver. Vehicles seldom bother to drive all the way to the top – but by the middle of 2012, when they do, it will be to collect a crop of lettuces. VertiCrop™ a Vancouver based company whose invention was one of Time Magazine’s top 50 best inventions in 2009 plan to build a legal grow-op on the roof. The system, which has been trialed in the UK, is claimed to produce 20 times the yield of field crops, using a fraction of the space and 92 percent less water.

The company claim the vertical growing system will produce 95 tonnes of fresh vegetables a year, equivalent to a growing area of 16 acres. Assuming the project proceeds, the 6,000 sq ft facility will be covered in a fluoropolymer greenhouse.