Mulching grass clippings provides more nutrients for your soil. As they break down, the clippings will release nitrogen, potassium, and phosphorus. These are essential nutrients that your lawn needs to stay healthy. To avoid a thick "thatch" of grass clippings on the lawn, be sure you have a reasonable grass-mowing height. Don't wait too long before mowing a lawn; mow frequently and consistently so clippings do not turn into thatch.
At the outset, mulching grass clippings into the lawn may feel like you are creating more waste. After all, bagged clippings get whisked away, while mulched clippings remain in the yard. However, be assured that you are not creating more waste - the clippings are organic matter that will decompose quickly. On the other hand, the plastic bags used to toss clippings do not decompose quickly. In fact, these plastic garbage bags fill up landfills.