Grumpy though I felt, I said the same to a Facebook friend.

I worry about a future where we'll be littering more and more of space.

Again, the car will not stay in orbit but will head out towards Mars. Also, it is not in a geosynchronous orbit so even if they left it where it is now, it would soon burn up in the atmosphere. 

(To avoid doubt, the smiley means I am not entirely being grumpy, just a light-hearted discussion).

One century's junk is another century's treasure, perhaps. I like to think so.

No one asked SpaceX to develop Falcon Heavy, the most powerful rocket in the world by a factor of two.

It was paid for by SpaceX's own money. An astonishingly small half billion dollars. (SLS, by comparison has absorbed $11+Bn and flown nothing, with a projected $5Bn per flight).

As this was just a test flight and had no customer, they launched Elon's personal car (instead of a "mass simulant"--dead weight) into space because it amused Elon.

They originally intended to send it out Mars orbit, but it looks like they ran the tanks dry and its going to the asteroid belt instead.  Why? As astronomer Phil Plait wisely points out, because they felt like it. No Act of Congress, no decade-long government/industry partnership, just a spur of the moment decision. 

That's a real mindset-changer from those who thought colonizing Mars was going to be done with a team of Four Elite Men.
As for the future of the car, someone ran the integration of the orbit out 10,000 years (yay, internet!), and it appears that the car's orbit will become progressively elongated, and will start to be perturbed by Jupiter more and more over time--there's a fair chance it will be ejected from the solar system altogether.  Starman indeed!
SpaceX's next vehicle will actually be able to collect Space Junk, among many other cooler things.

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Opening a car dealership.  

Rod here are the components of Rocket fuel.

 Where is the fossil fuel here? 

That's for solid rocket boosters like the Space Shuttle used (the exact components, in fact.)

Falcon 9 and Falcon Heavy's "Merlin" engines use RP-1 (tidied-up Kerosene) and LOX (liquid oxygen).

The BFR "Raptor" engines (next on SpaceX's design list) will use liquid methane (because you can make it on Mars) and LOX.

As for the pollution caused, RP-1/LOX burns to CO2 and water as does methane/LOX. Any realistic volume they could burn with even a busy space industry would be tiny compared to the airline industry or gas cars.  I.e., the planet is currently burning 35 billion barrels of oil per year.  

Also, there's no special reason methane production could not be made carbon-neutral (on Earth, anyway). In fact there's research to make one think it would only made that way in the near future.

As for electric rockets, the only design I've ever seen was designed by none other than Robert Bussard (I'll see if I can find the paper somewhere), and required a nuclear fusion reactor to electrically heat air as reaction mass.

[Edited to add:]  This isn't quite the paper I was thinking of, but it does mention the concept of the air-breather:   http://www.askmar.com/Fusion_files/Aneutronic%20Fusion%20Pro pulsion.pdf