“If CO2 really was a problem, which I highly doubt, why would you want to simply delay the inevitable by injecting into the ground?”
CO2 is interchangeable on a molecule for molecule basis for methane. Any natural gas reservoir that has held gas under pressure for millions of years will hold co2 for millions more. It’s not hard to find geologically stable sediments that have a caprock and miles of overlying sediments. Humans inject much nastier stuff down disposal wells every day in 50,000 barrel per day volumes in each well. Nasty as in salty, carcinogen contaminated, radioactive water from flow back of every oil well in the Midland or any other basin. Every oil well is a contaminated water well the oil/water split is almost always more water than oil in Midland it’s 1 oil to 6 water on average. This water must be isolated from th biosphere forever it’s far to contaminate to be allowed to mix with surface waters or worse in the fresh aquifers.
The point is humans have the technical knowledge to store gases and liquids underground for geological time scales. Nuclear wastes are also going to eventually be stored in deep bore holes it’s the way to be sure it’s isolated for millions of years. I personally developed,planned and supervised the drilling of over 75 deep salt water disposal wells one of my masters degrees is in Hydrogeology.
I don’t think it needs to be stored at all, but shipped out and re-used. Also, we know have the know-how to reduce nuclear storage to almost nothing. The new nuclear plants that are coming online are capable of recycling nuclear waste until it is nearly inert or inert. Nuclear storage is now potentially a thing of the past, or at least much reduced.