Interesting press release came forth from Nissan the other day. They were doing a bit of offsetting; there’s probably been a bit too much pomp issued about the new twin-turbo GT-R for the liking of the firm’s resident environmentalists, and so they sent out news that, come January, the number of wind farms at its Sunderland plant will rise from six to eight. And that inspired me to do a bit of adding up.

Nissan Sunderland will make 400,000 cars in 2007, split between Micra, Micra CC, Note and Qashqai models. Its wind farm will supply six per cent of its power; enough for 24,000 cars or thereabouts. I therefore reason that each windfarm supplies enough power to make 3000 cars sustainably. Seem fair enough so far?

There are currently around 40,000,000 new passengers cars being made globally every year. That means it’ll take 13,333 wind turbines to make all of the world's car production sustainable.

Using Sunderland as a model (where the original six-turbine farm cost £2.2mil), each 650kw turbine should set you back around £350,000. So by that measure, what’s the bill for making the whole car industry carbon-neutral? £4.6 billion. Sounds a lot, until you realise that Toyota is making around £7 billion a year right now.