they might be giants

The bloke on site here told me it takes 27 years for one windmill to break even on its carbon footprint, related to its construction, installation and maintance. He reckoned each windmill had about a 30 year life span before it needed replacing............errr.

I then read that the most important greenhouse gas is water vapour (90% of all greenhouse gasses apparently). So does that mean that if a hydrogen powered car only produced water vapour then thats a bad thing?

Think I'll have to get a solar powered de-humidifier