Most lawnmowers today are noisy and pollute more than cars, since they have no catalytic converters. The grass clippings are usually bagged and are often thrown out with the trash.
Many new mowers are now the mulching type.
Besides cutting the grass, they mulch it to small pieces that are left on the lawn. These fine pieces fall between the grass straws and decompose over a few weeks, giving nutrients back to the soil. This saves the work of gathering the clippings and provides free fertilization. There are a few electrical mowers available, some of them cordless. An electrical mower is very quiet, requires less maintenance and it creates less air pollution.