[Devilboy]

I still don't see where the carbon is going in this process. If it's not emitted as CO2 then what?

[anthonyb]

Fuel cells can be more efficient than just burning stuff (aka. combustion) so that's where the lower CO2 comes from - it's not a magic energy machine.

Look at dandelany's posts for the technical details.

[teilo]

The carbon is being vented. Just a lot less of it than the equivalent in combustion systems. Why less? Because fuel cells have a lot less heat loss, and so that means more electricity for the same amount of fuel. "Half the emissions" is relative to the amount of energy produced, not the amount of fuel put into it.