I had artificial turf installed in my yard a month ago for all of the good environmental impacts it has.  First and foremost is how much water you save with artificial grass.  The impact artificial turf has on saving water is huge.  Water is one of planet earth's most limited precious resources.  On average artificial turf saves about 70,000 gallons a year on an average residential lawn.  In no particular order, lawn mower and weed eater pollution is very harmful to the environment.  On average 1 hour of running a lawn mower is the same as 11 cards.  Another impact is the amount of gas and oil saved from no lawnmowers, weed eaters or the gardeners work truck they drive to you house.  Grass clippings is the single largest component of municipal solid waste at our cities dumps.  Toxic runoff is another reason to get synthetic grass.  The chemicals, fertilizers, pesticides, etc. you or your gardener put in your yard runs off of the lawn into the gutters and into our oceans and water supply.