Been a bit since I dropped in. Plant, do you know what the overall efficiency is of the various renewable plants Apple has put into place? I ask not because I'm inherently opposed to renewables, it's just that I keep running up against what seems to me several downsides to a strictly renewables approach.
First, since they're intermittent, and we still at this point have a baseload energy system, they have to be backed up by some form of fossil fuel infrastructure. My understanding is Apple feeds their green energy into Duke Energy's grid, rather than being able to power their plants directly from their solar and fuel cell sources. I think it'd be generous, based on Germany's current experience, to say that solar provides electricity about 12% of the time and wind about 20% of the time, I keep thinking this isn't making a huge dent in the overall carbon load, though I suppose every little bit helps to some degree.
Second, my understanding is the current carbon load won't really be felt for another 30 or 40 years - that we're currently experiencing the climate effects of the stuff we threw up in the 70s or 80s. In other words, we'd need to go in reverse on carbon - start actively pulling it down, and at a pretty good clip at that. (Actually, an insanely intense clip, but that's another discussion if we can't get to zero emissions anytime soon on renewables).
Third, it seems to me we're going to have at least a minimal need for liquid fuels for some time to come. Running mining equipment off electric sources might work, but tractors? And the raw hydrocarbon stocks that go into Apple (and most other) products will still be needed for some time as well. Plastics and fertilizers are the base of the modern industrial society.
So if we have to pull down carbon, and provide carbon stock, we'd need some sort of system that can turn the carbon cycle into one managed by humans. I can only conceive of this sort of thing in the presence of extremely large amounts of available, excess energy. And I can only conceive of that by some implementation of nuclear power.
But if you can explain how we do that with renewables, or if one or more of my assumptions are incorrect, I'm all ears
A carbon tax might or might not be something that could be implemented, but if the carbon cycle itself could be managed and the products salable, such a tax might not be necessary in the first place. I grant you, the thermodynamics are the first wall I run into every time I think about renewables.