Not so fast.

If you replace outdoor crops with forests, they'll sequester much more CO2.

In principle you can replace many acres of outdoor crops with one acre of greenhouse crops: with electric illumination you can make plants grow during nighttime, and with controlled temperature you they can also grow during the winter.

Irrigation also needs much less water in a greenhouse (because plants lose a lot of water via transpiration, and in a humid environment they transpire less). Not to mention that you can recycle the water in a greenhouse.

Irrigation is a big component of the energy expenditure of crops, but not the only one. All other components will decrease. Fertilizer, pesticides, tilling: you just don't need huge tractors to go miles and miles to the fields. You can have much smaller machines doing the job on the spot.

I'm not saying greenhouses are the solution to all the world's problems, but they shouldn't just be discarded outright.

The big deal here is the yield; the field outside my window yields 6 tonnes/hectare/year on a good year. The article mentions 117 tonnes/hectare and I assume it's on a yearly basis.

I can't imagine the production being more energy efficient than a regular field, but it sure saves space. I can imagine places like Singapore would benefit greatly since it could produce food locally.

That may be the principle but it's obviously flawed inasmuch as every square inch of cultivation needs its square inch of sunlight equivalent to grow. So now you're stuck with the energy cost of cramming (the sun) x (your stack depth) into your grow facility. You can certainly save on other inputs like water, but you lose the only free input available to agriculture, namely sunlight.

Plants don't use the whole light spectrum, at most they use 45% of the natural light. Solar panels can take advantage of the whole spectrum. Then, the indoor lighting will just shine the light that the plants can actually use (all growing lamps advertise that, see [1] for example).

Plants also don't use the light while they are just sprouting. Plants don't use light after you harvest them. And most importantly, plants don't use light where they are not.

If you have vast areas of desert, you can mount lots of solar panels. Lots of places are somewhat between pure Dunes-type desert and Ukrainian-type super fertile chernozem. In a semi-desert place, you might be better off just installing solar panels and building indoor farms. Think of places like Arizona, or Nevada, or, why not, Sudan.

[1] https://bioslighting.com/grow-light-spectrum-led-plants/grow...

Or we could maybe just keep growing things in places where they actually grow? Crazy, right?

This would not be the case if you where growing the wheat in a tropical climate where wheat would not normally grow.

For example think of Sudan. Most of the current supplies need to be shipped by ship and then expensively transported inland.

But Sudan has lots of sunlight.

Modern logistics systems are so efficient transportation costs are a rounding error for bulk commodities. How's the energy grid looking in Sudan these days?

There is very little logistics in Sudan. The roads are often unpaved. The cost of road hauling the wheat will probably double the cost.

But on the other hand there is lots of sunlight for solar.

So the proposal is to construct and maintain complex infrastructure in a place where simple road construction and maintenance are problematic?

Same, I have a green house. I have high tunnels and low tunnels too. They allow my family to grow nearly 100% of our plant needs year round. But I don't grow my grains in a tunnel or a house. I don't grow my pasture in one either. Green houses are a tool and there is a place for every tool. New tools get used for lots of things they aren't good for.

Eliminating those huge tractors injects a huge amount of inefficiency into your harvest operation.

How? Electrical equipment moving on rails seems more efficient than driving diesel tractors around on tires on dirt.

Modern combines sit idle when the harvesting period ends. So about 90% of the year. With indoor farming, you are not constrained by the seasons. You can rotate your crops, so you harvest some in January, some others in February, etc. Whatever machines you need for harvesting, spraying, tilling, etc, you can arrange to use each 100% of the time.

I personally think grains will not be economical indoors this decade, or maybe even next, but in some not very distant future, the majority of the agricultural products will be produced indoors, just like chickens are now. Of course, when that time will come, indoor farming will be perceived as bad, horrendous, anti-nature, etc, just like people perceive the industrialized chicken farms now.

Neat thing about idle equipment, it doesn't consume any inputs, so not real sure where you think you're going with that one. And yes, you aren't constrained by seasons. You're constrained by grid electricity rates, market prices for agricultural products, available labor pool, and the supply of dumb money naive enough to capitalize infrastructure projects that are balanced on that house of cards.

As I understand it, the stacked greenhouse is automated, so no labor, starvation-wage or otherwise.