Growing in warehouses or vertically forces you to substitute the sun with artificial lights: even if those are powered by the sun, there's a huge loss of energy in the system, hence increased cost.
This, to me, sounds like vertical farms in the grand scheme could be more efficient.
It also seems to require much more water than watering the plants in ground, I assume because they are getting maximum rate from roots and almost infinitely growing them .
For bugs in a greenhouse the least chemical method i've found is dumping c02. Can only use it in closed/controlled spaces tho. Blanket room in c02 for 12 hrs...literally just chokes any bugs. Plants are fine.
In your opinion, what's the main bottleneck wrt to resources?
I'm leaning towards productions suited for my region for this example, it would require tailoring to each regions climates/capacities if you were to do this everywhere. On the broad acre you essentially would do native grasses/root vegetables/shrub crops and runs of more traditional mono crops in dispersed amongst heavily Wooded paddocks. like 30-40% tree cover,30-40% perennial natives, 20-30% rotated mono-crop runs. You need to not stress the land too much where I am, and work with the droughts that come through (Australia). The whole goal of the broad acre is to produce a little food buffer but mostly material for nutrient creation.
So maybe you harvest/cut your native grasses a few times a year, bail it, inoculate it with fungi to eat it and convert it to a higher nutrient product for fertilizer if your running soil greenhouses. Or you could use mulched grasses to run a snail farm, that in turn feeds a aquaculture setup which you can strip the fish shit out of for nutes to supply your high density vert farm. Having the broad acre allows you to do other things too like maintain bee hives which can be brought into the greenhouse for pollinating.
Huge amounts of resources/capital required to set closed loops like this up...but on the plus side...once their setup, if you do things right like use high grade materials(e.g stainless for all your greenhouse piping/water setup) it can last for near infinite time with correct maintenance. Just good luck getting a investor who gets profit @ 10-20 year mark rather than 6-12 months. Market doesn't seem to like long games these days even if it is whats probably best for environment/long term sustainable high density farming.
Oh and also we need a robot that can pick fruit/veg and do maintenance that requires dexterity (think unscrewing a nozzle or pipe fitting). Bad. Labor is a killer for broad acre tree crops and stuff that requires a bit of dexterity for harvest (see Australia's current farm labor shortage).
The article linked presented the the efficiency of vertical farming in terms of produce/area. But as was pointed out in some of the comments on that article the cost of the greens grown on vertical farms was in the range of $15/pound [1]. Which is about 3x the price of organic greens at Whole Foods, or 10x the price of what you would find at Walmart.
[1] https://www.eater.com/2018/7/3/17531192/vertical-farming-agr...
But there are also energy and cost savings because you can remove most of the transport, which at the moment involves ICE vehicles, and the energy does not have to come from solar sources (just within renewables there are other options).
Longer term we can also imagine artificial lights powered by fusion power, which would probably be the best option in term of space saving and environmental impact.
http://hyperphysics.phy-astr.gsu.edu/hbase/Biology/ligabs.ht...
Edit: note the reason that most plants are green is because their growth is not limited by the amount of sunlight converted, so they can afford to throw away some efficiency e.g. they might be limited by water or mineral availability. Quote from same site: “Some plants and plantlike organisms have developed other pigments to compensate for low light or poor use of light. Cyanobacteria and red algae have phycocyanin and allophycocyanin as accessory pigments to absorbe orange light. They also have a red pigment called phycoerythrin that absorbs green light and extends the range of photosynthesis. The red pigment lycopene is found in vegetables. Some red algae are in fact nearly black, so that increases their photosynthetic efficiency. Brown algae have the pigment fucoxanthin in addition to chlorophyll to widen their absorption range. These red and brown algae grow to depths around 270 meters where the light is less than 1% of surface light.”
Edit 2: plant photosynthetic efficiency in capturing CO2 as sugars: “the theoretical efficiency is 114/381 or 30%. Remarkably, Moore, et al. report that 25% has been achieved under laboratory conditions. The top efficiency they reported under natural growing conditions was the winter-evening primrose growing in Death Valley at 8%”
That's a big 'if', though, considering that you'd need to offset both the land taken up by the solar panels and the losses of the electricity transmission.
Couldn't one construct pylons outdoors for planting? I don't see why it wouldn't work if you constructed it narrower at each successive plant height.
Some indoor vertical farming I've seen rotates the entire vertical structure, necessitating only one light facing a section of the column. I would expect this kind of rotation might help outdoors as well.