All airports are dirty, there's no avoiding it, and LaGuardia isn't any worse than say Liberty or Midway or Stapleton. I don't have anything against LaGuardia but it's not green, and expecting the thing under it's approach pattern to be green is a big misrepresentation of what Rikers Is. is capable of.

What's planned for Rikers is needed, although I'd go much further ie moving the nearby Produce Terminal and ConEd facilities around - things that work well with new rail - but none of this is green. Though, at that point a whole LaGuardia/GCP reconfiguration should also be considered as it's a common complaint, especially if LIRR or subway expansion is considered. Turning Prison Island into Infrastructure Island is a good idea, but it's not going to be environmentalist. It's going to be a big dirty thing full of big dirty machines that preform some function normally done in the Bronx or Brooklyn.