A mulching lawn mower is similar to a regular lawn mower, and in many cases mulching may be a feature found on a regular lawn mower. Mulching returns the grass clippings to the yard where they quickly decompose adding water and nutrients back into the yard.
Mulching mowers work by creating mulch out of the grass and leaves they cut. This is accomplished in two steps. First, mulching mowers will have a second, smaller blade located above the main cutting blade. This second, or mulching, blade cuts each piece of grass or leaf debris that was cut off by the main blade, reducing it in size and making it easier to break down in the lawn.
The second step is circulating the clippings inside the deck of the mulching mower so that they are cut several more times into still finer pieces. This happens because mulching mowers have no catch bags or debris ejection holes on the side of the mower to eject clippings like a standard mower does. Instead of leaving the cutting chamber the clippings stay trapped in the mower until they are cut into fine pieces that settle into the lawn, quickly decomposing and aiding the growth of the lawn.