Buy an electric lawn mower and electric string trimmer for clean, quiet, and odorless lawn care. Electric models cost almost exactly the same as gas models, plus your ears and lungs will thank you.
All the Facts
During high school and college, I ran a lawn mowing business so I have plenty of experience spending the day walking behind a loud, exhaust spewing engine. Low cost lithium-ion batteries have solved both issues. Cordless electric lawn mowers are both quiet and exhaust-free at the point of use. Battery costs have declined to the point where electrics are now cost competitive too. There is no reason to go with gas powered equipment when getting a new lawn mower or weed eater. You will be much happier with the quiet, clean, and odorless electrics for cutting your grass.
If you are unconcerned about the quality of life argument (quiet, clean, odorless) and want to know how it helps out the environment, there is reason to rejoice. Electric lawn care makes a big difference. If you haven’t seen my page on electric vehicles yet, that would be a good primer for understanding just how extreme lawn care emissions are. The EPA regulates car emissions much more heavily than small engines, but even with the higher regulatory bar, electric cars have lower emissions than gas powered cars. If you have a gas powered lawn mower built before 2012, then the hour you spend cutting your lawn gives off the same amount of HC+NOx as a car driven 257 miles, and the same CO as one driven 401 miles. The average number of lawn cuttings a year is between 25 and 30. Cutting your lawn with a gas mower instead of an electric equates to driving your car an extra 6,375 to 12,000 miles depending on the number of cuts and whether you calculate for HC+NOx or CO. The department of transportation puts the average miles driven at 13,476 for 2015. If you aren’t a big driver, your gas mower is producing more pollution than your car.