Mostly? We mine minerals and refine them with: Petrochemical sources. Which, you might also worry about running out of, in about as short order as topsoil. T

Mostly? We mine minerals and refine them with: Petrochemical sources. Which, you might also worry about running out of, in about as short order as topsoil. There was another commenter here with more expertise on actually growing things this way - they suggested that leafy greens were the only thing we could grow efficiently with this method. Which does have a certain air of "truthiness" to it.