How come people describe fuel cell cars as "clean"?

Question

Supposedly they just put off water and CO2, but CO2 is a big greenhouse gas right?

Answer 1

Technically, this is only what is put into the car. It is considered to be clean because the output of the car is water. This does not contribute to greenhouse gases in any way.

Answer 2

The cars are made from aluminum and steel (lots of coal burned to make it), plastics and paints (oil product), so these cars are not "clean".  It would be better to get rid of leasing cars and people would have to buy their cars instead.

Answer 3

Providing that the hydrogen the use is obtained from clean energy ie wind, solar, hydroelectric then the only byproduct is water, H2O . There is no CO2 involved.

Answer 4

Because even though they take way too much electricity to run, they 'only produce water vapor'.

They don't put out CO2...... Just water.

Answer 5

If running on pure hydrogen obtained from ? (Jupiter?), they emmit no CO2.   If they obtain hydrogen from some hydrocarbon, then they emmit the CO2 at some point, but are around 80% efficient at converting the fuel to usefull energy compared to 35-40% for internal combustion engines.

Answer 6

I don't think they make co2, h2o goes in, water and ozone come out. (o2). maybe from hydrogen burning? Can't be to much.

Answer 7

People believe hype and don't consider the bigger picture.  However - the cars are greener in that they translate to the gas equivalent of many more miles to gallon.  That is greener and cleaner - if not perfect yet.  Trading exhaust pipes for coal stacks and nuke waste is not cleaner.  It is more efficient.  And electric cars will be super fast.

Answer 8

If you put only hydrogen (H2) into a fuel cell car, then all you get out is water (H2O) and energy.

But you need to create the hydrogen (H2) somewhere.  Right now, all the hydrogen (H2)  is created using fossil fuels (C#H# like CH4 or C2H6), so you are emitting carbon  (C) to make the hydrogen (H2).  

"But wait!" (some people say) "Can't we just make hydrogen (H2) from water (H2O)?"

This would equate to a perpetual motion machine.   If you could separate the hydrogen (H2) from the water (H2O) without the use of energy, then when you created the water (H2O) again (in your car) it wouldn't release any energy.    You either pay energy to separate the two molecules, and get paid energy when they combine, or you don't.

The reason that fuel cell cars, or any other zero emission vehicle, is clean is because all your greenhouse gas emissions then come from one place - a power plant or hydrogen plant.  And its easier to control emissions from one big plant than it is from a bajillion cars.  

At least, that's my understanding of the situation.

Also, I've put the rough chemical letters throughout this because to understand this process, its important to recognize that we are talking about putting together and taking apart three different types of elements, really.   Hydrogen, Oxygen, and Carbon.  And it helps (me anyway) to think about how they are added and subtracted as the fuel moves through the process.

Great question.