I'm curious, does it come out of the engine as water or steam? Where does it go? Water vapor is a more significant green house gas than CO2.
A better idea may be to place induction coils in the road beds of highly traveled routes. Cars could use this power on the freeway then use battery power during the last mile to the destination. There are no vehicle emissions in that, not even water vapor.
"Water vapor is a more significant green house gas than CO2."
That's my concern as well. More water vapor>>more clouds>>global cooling>>more rain/flooding.