yes I would agree the mass to orbit is the problem. I was hoping with the right size emf there could be obtainable forms of matter in orbit that may someday lead to harvesting steam or water particles from the dust obtained. That’s to say if there is anything obtainable matter which there is thought to not be any but in my day we also thought the moon was below freezing. I love talking about my ideas. Even when they are met with an abrupt no
The space farming is for when and if we ever sustain 100 billion.population or more. I do see if we find alternative solutions to orbit and water retrieval it would be practical and much more open than underground farming
EMF = electromotive force so I fail to see the connection here, whislt there is EMF between charged particles, the electroweak and electrostatic forces will pay a larger role and have no bearing on the quantities of mass required for farming in orbit.
Given costs and the need for gravity, it would make far more sense, if you wish to preserve the arrable surface of Earth, to use floating farms on the oceans or use enclosures that cover desert areas. Solar power and wave power could be harnessed for electrical energy, you have immediately removed the biological problems caused by the the lack of gravity and the preponderance of radiation.
If you wanted these farms to provide food to colonists, then building them on the lunar surface would be the logical next step, the domes could be protected against radiation, solar insolation could be controlled, it could provide ample electrical energy and you have the advantage of gravity - it may be lower than Earth, but plants would likely adapt fairly rapidly.
The same would apply to Mars - this could also act as a food production facility for any facilities that are later built within the asteroid belt on the likes of Ceres, Pallas and Vesta.