Like chain saws, many lawn trimmers use an oil-and-gas mixture that sends pollutants into the air. While handy for keeping a lawn looking great, gas-powered trimmers offend the senses and the environment.
New, green lawn trimmers that are currently gaining in popularity run on propane fuel instead of gas. Propane-powered trimmers are far easier to use; you don't have to worry about clogged lines and carburetors. Also, gas-powered trimmers can be difficult to start in certain conditions, but propane trimmers feature instant start-up.
Propane is safer for the environment because it's neither toxic nor caustic. If you spill it, no harm will come to the soil or the water.
You can also go green with cordless designs, which have rechargeable lithium-ion batteries that are reported to run up to 45 minutes on a single charge.