Daiwa, that is a very good question. The answer is that Tesla pays for the electricity at supercharging stations for the life of the Model S. However, you must have purchased the supercharging capability in your car (standard in all 85 kwh Model S like mine, optional on 60 kwh versions.) So, essentially you are paying a fixed amount up front to be able to use the superchargers as much as you want, whenever you want for the life of the car. Not for as long as you own it now, for the life of the car. Subsequent owners could you use them too. As a taxpayer you aren't paying a thing for this. Now, I could lose out on my free long trip refueling if Tesla went bankrupt, but I am willing to risk it And if you are ever in my neck of the woods (Wine Country California) I'd be happy to give you a ride in our Tesla as a taxpayer bonus. You are making out like a bandit!
There are a lot of misconceptions about carbon footprint as it relates to electric cars. The reality is they can be either "a bit better" than a traditional car over their lifetime to unbelievably better over their lifetime depending on how the electricity you use gets generated as you suggest.
Consider that the Model S is rated at 89 mpge. That means if you look at energy is used to generate the electricity and how much electricity the car uses, it nets out to about the same as a car that gets 89 mpg. Already that's pretty amazing considering this is a a BIG, fast sports sedan, not an econobox!
So even if you are using dirty power generation it is fairly clean compared to most gas or diesel cars. How much cleaner depends on where you live. The worst area in the US is West Virginia (they burn coal for all their power more or less) and the best in the US is, I think, New Hampshire (mostly nuclear power there.) Then again, if like our family you have solar installed to more than take care of the yearly electric use of the vehicle the net operating carbon footprint is zero! Hard to beat that from a CO2 standpoint.
As to disposal... probably not an issue there. The battery packs can be re-purposed for grid storage once the car is no longer viable and Lithium ion cells can be recycled.