Vertical farming

Vertical farming is the idea that food could be grown in tall towers with multiple floors, which is supposed to save space and use less land (thus saving more of the environment), but on close examination we see that it doesn't.

Not a solution to feed the world

Powering the grow lights

Natural sunlight is proportional to land(...)( Sure, technically you could argue that a tall building captures more sun than the land it sits on, but that's just because it obscures the sun on the land beside it. ). In vertical farms, the amount of real sun is quite limited. Grow-lights are needed:

Thought experiment

If all crops were grown in vertical farms, how much energy would be needed to power all the grow lights?

photosynthesis.spectrum_of_sun

How much of the sun's energy spectrum can plants use for photosynthesis

By factoring this in, we're being very charitable to vertical farming, by assuming the LED lights (unlike sunlight) are entirely frequencies of light that plants use.

energy.tfc (calculation loading)

In other words, we would need _ times more energy than the world currently consumes!

Since most energy currently comes from fossil fuels, this would be disastrous for the environment.

But what if the energy came from renewables?

We already have a hard enough time scaling up renewables - but let's imagine it was easy. Still, vertical farms would defeat their entire purpose: They wouldn't save land.

(calculation loading) In other words, to grow an acre worth of plants(...)( and I'm not talking about the footprint of the building. By "grow an acre worth of plants", I mean for example having a 1/8 acre building with 8 storeys ), you would need over _ acres of solar panels!

To convert...

sunlight → electricity → back to light again

can never be as efficient as...

just using the sunlight directly.

The land requirements for wind power would be even higher. Keep in mind that wind power is still indirectly a kind of solar power: winds are caused by the sun heating the air.

Uranium is far too scarce to power the grow lights with nuclear fission. Maybe fusion power could do it someday. Until then, vertical farming is just a bad idea.

But doesn't it take energy to ship food from farm to city?

Yes. Just nowhere near as much as what vertical farming would take.

But what about shade crops?

Shade crops could already be grown in the shade of full-sun crops. Most of the crops that feed the world require full sunlight. This is because calories & protein require energy in the form of light shining on the plants.

There might be a very small niche for growing low-calorie greens in vertical farms in the city, just so people can enjoy herbs at their absolute freshest.

Cases where vertical farming might actually be a good idea

Growing mushrooms

Mushrooms don't get their energy from the sun - they get their energy from fiber. Since food crops have inedible fibrous parts, there is plenty of material to cultivate mushrooms on. Mushrooms could be grown in tall buildings or deep basements with no light at all.

Disambiguation

Some people use the term "vertical farming" to refer to something different: a rich layered polyculture - no multi-storey buildings involved. This type of "vertical farming" actually has good potential to feed the world.