IIRC in a documentary about spanish produce vs german greenhouse produce they calculated that german produce is much higher in co2 output than spanish, even when the spanish produce is delivered by a semi all the way from Spain! Simply because in spanish climate there is no need for a greenhouse to grow e.g. bell peppers or tomatoes.
I only found a german source: https://www.umweltdialog.de/de/verbraucher/lebensmittel/2015...
it says:
German, heated greenhouse outside of season: 9.3 KG of CO2 per KG tomatoes (well, that is unexpectedly high)
Non heated greenhouse: 2.3KG of CO2 per KG tomatoes
open land in spain: 0.6KG of CO2 per KG
open land in Germany in season, conventional: 0.085KG of CO2 per KG
open land in Germany, organic: 0.035KG of CO2 per KG
although it's from 2015, I don't think that much has changed in 5-6 years to make up such a big difference between heated, nonheated, open land and regional. It also factors in transport from Spain to Germany which is why open land in spain has a higher co2/kg than german open land.
edit: of course I can't find anything that compares vertical hydroponic farming to greenhouses, all I can find relates to CO2 dosing in greenhouses :/
it says:
German, heated greenhouse outside of season: 9.3 KG of CO2 per KG tomatoes (well, that is unexpectedly high)
Non heated greenhouse: 2.3KG of CO2 per KG tomatoes
open land in spain: 0.6KG of CO2 per KG
open land in Germany in season, conventional: 0.085KG of CO2 per KG
open land in Germany, organic: 0.035KG of CO2 per KG
although it's from 2015, I don't think that much has changed in 5-6 years to make up such a big difference between heated, nonheated, open land and regional. It also factors in transport from Spain to Germany which is why open land in spain has a higher co2/kg than german open land.
edit: of course I can't find anything that compares vertical hydroponic farming to greenhouses, all I can find relates to CO2 dosing in greenhouses :/