Ah, of course, the energy fairy! But I think she lives in the nucleus and makes a hell of a mess when she is dragged out of there.
John, I agree that petrol mowers are terrible polluters. It's pretty obvious. You can see it, smell it, hear it. They are such a violent brute-force instruments, and only to cut some blades of grass. To my mind, they are very representative of modern western civilisation's attitude to the world around us. ... Well that's my excuse for neglecting doing the mowing anyway.
PS. Here's a pic of my enviro-mower. I just need to get a proper handle for it ... and learn how to tell the grass that needs cutting apart from my feet which do not ...