[philipkglass]

Urban farming only makes sense for high value, easily perishable produce. Fresh herbs, leafy greens, tomatoes, and other salad ingredients can be produced with higher quality when they are harvested and used on the same day, and when the plants don't have to be bred for shipment-and-storage durability. The real benefit is superior flavor and texture for quality-focused, price-insensitive eaters.

Note that this product site touts how much lettuce the system can grow.

More radical claims about how vertical farms will reduce CO2 emissions or feed a growing world population are aspirational to the point of delusion. Vertical farming isn't going to replace the calories that people get from potatoes and beans grown in big plots of dirt outdoors. If you ate potatoes grown in a nearby vertical farm instead of ones grown in Idaho and shipped across the country, you'd actually be increasing your carbon footprint.

It takes only a little energy to move a potato a thousand miles cross-country. It takes a lot of energy to grow a potato under artificial light. Even though renewable energy is ~20x better in life cycle emissions than fossil energy, it takes more than 20x as much energy to grow potatoes under artificial light. From a CO2 life cycle perspective you're better off eating potatoes that had ordinary diesel powered tractors, trains, and trucks involved in their production and delivery than to eat potatoes that were grown in a wind-powered vertical farm next door to you.

[mandelbrotwurst]

This is a false choice. Urban agriculture doesn't need to mean indoor agriculture / relying on excessive electricity / complex equipment etc.

Cities can be plenty dense while still having enough space for people to grow potatoes for themselves and their neighbors.

[philipkglass]

You’re right. Urban farming with sunlight is fine. My energy arguments only apply to growing under artificial light.

[Kalium]

Is it? That seems like a poor use of space that could be dense housing, commercially productive, or a wonderful park.

[jurip]

It would be helpful to quantify "plenty dense" here. Paris has a population density of 21498/km2. Turning that around, that's roughly 46 square meters per person. That doesn't leave a whole lot of space for a potato plot if you're supposed to cook and eat those potatoes somewhere, too.

[natmaka]

Source?

AFAIK traditional artificial light sources do indeed dissipate much more energy for the same amount of 'useful light', and also produce so much heat that they cannot be placed near the plant.

Is artificial light mandatory in urban farming? Aren't some (non fiber-optics-based) "light tubes" able to transmit light along with the necessary UV?

[mandelbrotwurst]

Nope! You can grow plenty of potatoes with sunlight in a plastic barrel on the balcony of your high-rise apartment.

[hanniabu]

Artificial light isn't necessary, but it's more space efficient and allows you to grow more plants per area which helps with the typically high land cost per square foot in urban areas.

[cosmodisk]

These arguments are often lost shen people believe in something blindly. Tomato grown in Spain and flown to England will end up costing our earth less than the smae tomato grown in England because of additional energy to keep it worm required.

[natmaka]

Isn't cogeneration, or any other type of "waste heat" recovery (for example from datacenters https://www.datacenterknowledge.com/data-centers-that-recycl... ) able to at least able partly solving this?