I don't know all the details of vertical farming, but there is more to it than energy efficiency. The controlled environment is supposed to remove the need for pesticides, bring fertiliser use right down to the minimum possible, and then there's the efficiency in logistics of growing food closer to point of consumption, especially when temperature/humidity/ light control lets you grow exotic stuff locally year round.

Whether it is worth it overall is unclear. Probably the answer is "sometimes, it depends on the situation".

Rooftop greenhouses?

I get where you're coming from. (Also, "profitable" has nothing to do with "ecologically responsible.") I have a lot of the same concerns about bringing plants indoors and having to meet their needs using a lot of energy and material inputs when growing them outdoors with free energy and fewer resources works so well. However, one thing outside can't do easily is multiple layers of plants. If we can find a way to bring the vertical part of vertical farming outside, I'd be more supportive of it. It's just a tough problem to solve when it takes a lot of money to build the structures and the structures can get wiped out in one bad weather event.

Would be way better if they used mirrors, or transferred sunlight through optic fibers. I mean if possible.

it takes aboit 30m² of solar pannels to grow what could be grown on 1m² using direct sunlight.

Where can I read more about this? I had thought that solar panels absorb a lot more energy than plants can, and I would think that collecting energy across a wide range of wavelengths and then using that energy to emit only specific wavelengths could give plants more useful light. But I admit I don't know how each is optimized for different wavelengths.

Disagree. I won't buy anything else and the quality is exceptional and the price reasonable. I won't buy American at any price as GoodLeaf is a part of our food sovereignty.

Also, US produce isn't safe.

Dude a head of lettuce is 4 bucks at my grocery store.

I'll pay the difference, which isn't as much as it used to be, and I'm supporting novel food tech, sustainability, and I don't have to wash or cut anything.

Bring back 99 cent lettuce heads from the good old days of 2023 and I'll chop my own salads for sure.

I'm not so sure, lettuce and leafy greens like the kind used in salads (basically all of what goodleaf makes) are usually cheaply priced in comparison to many other staples like meat, dairy, dry goods etc. and are extremely seasonal goodleaf may be twice as much as those but it's also fully Canadian, all it's inputs can be Canadian too, doesn't have the same issues with contamination by natural means and methods (cough, Taylor Farms, cough) and is made year round unlike normal produce. In the middle of the winter i can have a salad that costs me 75c to $1 for a portion or with goodleaf it may be just 50c to $1 more to know I'm supporting Canadian eating healthily and am not going to get screwed over by a bad rain that washes fresh cow manure from a nearby field onto collected lettuce/spinach. From what I've seen when times get tough people tend to stop buying expensive meats or fancy imported goods and tend to buy more veggies/fruits/produce to stretch what they do have. for example maybe steaks are off the menu and instead they buy cheap chicken drumsticks or pork chops that cost a half to a third as much, and instead add a salad or some local veggies to their plate to stretch their dollar (fat least from what I've seen).

Honestly, this is the only lettuce my family buys now. Its Canadian and the quality is way better.

It's part of the vice market, which tends to do well in bad economic times as many people don't tend to reduce vice spending with discretionary spending reductions, though they might redirect their spending towards products that give more bang for the buck. Though in my experience, weed is pretty cheap for how long it can last, especially since prices have come below the black market prices pre-legalization.

Though that black market still exists with even lower prices now and lack of funds might push more towards it, which will probably lead to a ramping up of enforcement.