I don't know what you've heard and where you've heard it but there is generally a lot of misinformation floating around and most of it is being sponsored by lobbies with an agenda to keep the oil and gas companies going. So, I would suggest not taking any of that at face value. Including what you hear in threads like this or from me.

Vertical farms are essentially closed systems where nutrients, energy and some water goes in and produce comes out. There's a bit more to it of course but that's the general idea. They are climate controlled environments where light is provided via grow lights. In short, it uses energy which needs to come from somewhere.

You are confusing power requirements and greenhouse gases. Mostly these things use some form of sustainable power. Either sourced indirectly via some electricity provider; or directly with e.g. solar panels. If you think about it, the number one expensive consumable here is electricity and the cheapest way to produce it is via renewables. It's that simple. Why would you get more expensive energy if you can get it cheaper. Keeping all those ACs, lights, pumps, etc. going you are going to have to figure that one out or deal with competition that is smarter than you on that front.

There are probably a few farms that are forced to buy via the grid and are hopelessly dependent on their local coal burning monopolists. Not a great business plan but the good news is that coal is rapidly becoming a very unfashionable way to produce power due to the fact that it is expensive and dirty. It being expensive cuts down on energy margins and causes coal dependent producers to be dealing with awkward things like going bankrupt and being forced to pay more for their coal than they can charge for the resulting energy when wind is blowing and the sun is shining. Gas has similar issues, as people that pay gas bills these days can vouch for. Mine went up by 2x recently. Not great.