With the average age of a farmer in Japan at 67 and few candidates to replace those dying out, the country has been forced to become a pioneer in so-called vertical farming.
Globally renowned firms such as Panasonic, Toshiba and Fujitsu have tried their hand -- converting old semi-conductor production lines with varying levels of success.
One of the few companies to turn a quick profit, Spread produces 11 million heads of lettuce annually from its latest factory in Kyoto, a vast sterile area where the vegetables are stacked on shelves several metres high.
Machines shift the lettuces around the factory to areas where the light, temperature and humidity are ideal for that stage of growth. The process works without soil or pesticide, and only a dozen or so humans are employed to collect the lettuce at the end.
Other countries have employed vertical farming techniques -- notably in Denmark and the United States -- but Japan's population crisis means the farmers are dying out, with question marks over how the world's third-biggest economy will feed itself.