[lathyrus_long]

> High calorie and/or high fiber foods require complex rhizospheres which is currently only found in healthy soil.

What is your source for this claim? Major grains (wheat, corn, rice, etc.) grow fine hydroponically--I've actually seen modern conventional agriculture described derisively as a hydroponic system using the sterilized natural soil as its inert medium. That description seems basically correct to me, though I don't think it's necessarily bad. Production of grains in systems analogous to hydroponic vegetable production would certainly be possible, just currently uneconomic:

https://www.pnas.org/doi/10.1073/pnas.2002655117

The major benefit of hydroponics is in achieving very high yield per acre. This is important e.g. when growing perishable vegetables in expensive greenhouses near densely-populated areas. For grains that are readily dried, stored, and shipped, it's currently far cheaper to cultivate more acres in remote areas at lower yield per acre.

The "petrochemical" claim is also confusing. The point of hydroponics is that the plant gets nutrients from the solution, not from the inert substrate. Typical hydroponic substrates may be plant-based (e.g. coir) or not (e.g. rockwool), but in neither case are they providing significant fertility, nor making significant use of petrochemicals. Obviously their energy inputs for production and transportation often come from petroleum; but that's true for almost any human activity today, including organic agriculture. A few niche applications do use petrochemical-based substrates (e.g. phenolic foam), but very rarely.

The synthetic nitrogen fertilizers dissolved in the nutrient solution often use hydrogen from natural gas, since that's the cheapest source, but could use any other source of hydrogen (e.g., electrolysis of water) instead. Here's an article studying those economics:

https://www.frontiersin.org/articles/10.3389/fenrg.2021.5808...