That means we would have to build our own fusion reactor on Earth or on Mars. Sure, it would be worth it on Mars since you don't have any other choice but on Earth? Anyone who thinks that is arguing in bad faith.
You don't need to spray because you control the environment, you don't need to transport as far, and planting and harvesting won't use fossil fuels (unless that's your only source of electricity).
1) you still have to use actual soil and thats full of bugs and organisms already
2) if you aren't fertilizing you won't get anywhere near the yield farmers do and you won't be competitive on cost.
Harvesting will still require the use of whatever harvesting technology there is. If we can't competitively build grain harvesters with electricity outdoors its unlikely that you'll be able to do the same indoors. You'll notice no pictures or description of how they harvest - they aren't doing it by hand and they don't say its by electricity, and even if it is do you think the sun provides more energy for free over the life of the crop vs the one time its harvested?.
This doesn't seem very interesting as it stands now.
This article doesn't say, but vertical farms almost always grow hydroponically, using sterilized inert media (like coir) or inherently sterile inert media (like rockwool). The water and fertilizer are delivered together by drip irrigation. Some farms may instead use no medium at all, like in NFT or DWC. With precise control over the plant nutrition, this can achieve higher yields per square foot than soil, making optimal use of the expensive indoor space. (I think grains are particularly unsuitable crops though, per my other comments here.)
In theory it's possible to run completely free of insects, with cleanroom-like precautions, and I think some facilities do. I think it's more common to live with some level of insect pests though, since it's so hard to avoid introductions and so destructive when they occur--with no natural predators, they can multiply far faster than in nature. That implies some level of pesticides, deliberately introduced predatory insects (which are particularly effective indoors, since they can't fly away), etc.
you're still fertilizing then, its just in the liquid you're using. I suppose that helps against nitrogen runoff which is bad for water bodies so thats a plus.
Harvesting won't use what? Are you proposing we, as a species, revert to harvesting the equivalent of a few hundred million acres of cultivated land by hand?
It's indoors, probably on many narrowly spaced floors, so you're hardly going to use a combine harvester! There would be some much smaller electrically-powered robotic system.
So now we're proposing to replace an insanely efficient harvesting system that has been refined and perfected over the course of the last century with what? Rasberry Pi's and some off the shelf stepper motors? Best of luck with your endeavor.
