Such a precise growing environment guarantees a bumper crop. In normal outdoor fields, farmers might produce five harvests a year of these types of microgreens. Inside a greenhouse this can increase to 20 harvests a year. But, here, deep beneath the streets of London, hydroponics guarantee an annual yield of 60 harvests or more.
One scientific expert in the sites under urban will to field is Dickson Despommier, professor of microbiology at the University of Columbia, in New York, and author of The Vertical Farm: Feeding the World in the 21st Century, the book in which he first coined the phrase "vertical farming". He says we need to act now to feed the planet's burgeoning population.
But cutting down rainforests to create farmland is not the answer, he stresses. That simply adds to global warming because trees are so vital in storing carbon. "What happens in a few decades' time when there are 10 billion mouths to feed?" he asks. "How do we supply food without deforestation? We have another method for growing food: farming indoors."
Despommier envisages a time in the not too distant future when all new city buildings will include vertical farms that will feed the residents living in them.
Indeed, indoor vertical farming is sprouting up all over the globe. Some of the farms are enormous. In the United States, for example, there is AeroFarms, Bowery Farming, Kalera and Plenty. Japan has a farming operation called Spread.