Photos: Giant vertical farm opens in Denmark

A purple glow illuminates stacked boxes where lettuce, herbs and kale will soon be sprouting at one of Europe's biggest "vertical farms" which has just opened in a warehouse in an industrial zone in Copenhagen.

Fourteen layers of racks soar from floor to ceiling in this massive, 7,000-square-metre (75,350-square-foot) hangar used by Danish start-up Nordic Harvest.

The produce grown here will be harvested 15 times a year, despite never seeing soil or daylight. It is lit up around the clock by 20,000 specialised LED lightbulbs.

In this futuristic farm, little robots deliver trays of seeds from aisle to aisle.

The large aluminium boxes are mostly empty for now, but lettuce and other leafy greens will soon be growing.

Some 200 tonnes of produce are due to be harvested in the first quarter of 2021, and almost 1,000 tonnes annually when the farm is running at full capacity by the end of 2021, explains Anders Riemann, founder and chief executive of Nordic Harvest.

That would make the Taastrup warehouse one of Europe's biggest vertical farms.

These urban facilities have unsurprisingly received a cool welcome from rural farmers, who have questioned their ability to feed the planet and criticised their electricity consumption.

But Riemann stresses the environmental benefits of his farm, with produce grown close to consumers and its use of green electricity. "A vertical farm is characterised by not harming the environment by recycling all the water and nutrition or fertiliser," says Riemann, who uses no pesticides.

Urban farming could even allow land exploited by single-culture farming to be reforested, Riemann said.

First developed around a decade ago, vertical farms have taken off in Asia and the United States, which is home to the world's biggest. The idea has slowly started to catch on in Europe.