You can’t. It’s as simple as that. Harsh but true.
Drive a diesel, because it’s more fuel efficient? Fine and dandy. Just remember that even with the exhaust scrubbers and convertors, diesels chuck out lots of polycyclic hydrocarbons. These sound nasty, and indeed they are. They’re as carcinogenic as all get out.
A hybrid? Bully for you. But see my later comments about electric cars.
Looking forward to hydrogen powered cars, because all they emit is water? Well, that’s true, but it’s a classic NSTAAFL. There’s not much hydrogen around (unsurprisingly, since it’s highly reactive, which is why it burns), so it’s produced by electrolysing water. Electrolysis needs electricity. This is produced by power stations, and they burn coal or gas or shale oil, or whatever. Unless they’re nuclear powered, which isn’t very green at all. Also hydrogen isn’t very calorific, so you need to burn a lot of it to get a decent head of steam up, as it were.
Electric cars. Gotta be good news, eh? Zero emissions? Nope, not so. They don’t emit anything, but they too need electricity, and again NSTAAFL. All that happens is the emissions are a long way away from the car.
Electric cars need batteries, and even modern batteries are heavy for the amount of power they can store. A gallon of petrol weighs about 9 lb, and contains a heck of a lot more energy than a similar weight battery. So they need to put a lot of batteries in a car to carry enough energy to get it to go a decent distance at a reasonable speed. The cars will therefore tend to be heavy.
The manufacturers get round this by making the rest of the vehicle as light as possible. Aluminium is the weapon of choice here, and that metal consumes prodigious quantities of energy (electricity) during smelting. There’s also a lot of use of composites, or plastics in everyday language. Those are made from petroleum. No other feedstock for plastics is viable just at the moment.
The batteries themselves are full of toxic metals. These metals are derived from ore, and mining and refining ores, let alone smelting, is a filthy process. It requires thousands of gallons of water per tonne of metal, and the run-off and tails are seriously toxic, because they contain other heavy metals whose concentration is sharply increased by the processing. Then when a battery reaches the end of its life, what do you do with it? You can recycle some of it, yes, but a lot of it is simply defunct. How do you dispose of all that toxic crap? Beats me.
Then there’s simple things such as the cables to carry your clean energy round your zero emissions vehicle. The best metal for making cables is, for a variety of reasons, copper. There’s miles of cable in even a small car. Have you ever been anywhere near a copper mine/smelter? I have. Nothing grows for miles and miles around. Nothing.
There’s also the thorny problem of items such as tyres. They’re a swine to dispose of or recycle. Lubricants. Horrible things. Dust from brakes? Don’t breathe too much of that. Got aircon? Shame on you. All aircon systems leak refrigerants, and they’re all either greenhouse gases, or they cane the ozone layer, or both. Even that rather fetching special edition paint finish is made from oil.
In conclusion, if you think you’re smart, and feel smug about your zero emissions vehicle, then don’t. It’s better than an 8 mpg gas guzzler, but it’s not as clear-cut as you think.