Back in 2012 Dan Delventhal and Marty Murray mowed 4 acres of grass in Greenwich with push reel mowers to make a statement about air pollution and lawncare.
It was 95 degrees out and they pushed 3 mowers at a time each, mowing all 4 acres with no gasoline.
Gas powered lawncare is 5%+ of the US air pollution – They avoided 4,000 automile equivalent emmisions in one day.