In general, the Vancouver 2010 games are said to be the greenest in history.  The medals were recycled from trash and the shuttles going from game to game where powered by hydrogen fuel cells, producing zero emissions. Also, the Richmond Olympic Oval in which speed skating took place uses a rainwater catching system that supplies the water for the toilets and irrigation.  Overall, Vancouver has changed the face of the Olympic games. 

Probably the greenest events were cross country skiing, biathlon, nordic combined and ski jumping. These did not use stadiums that would contribute to emissions. These sports were hosted in the Whistler Olympic Park. Being outdoor events these quite possibly were the greenest events.