Sawdust on lawn - make sense?

Sawdust won't do a thing for the lawn until it has decomposed and the decaying process robs valuable nitrogen from the soil while it's happening. Your friend is offsetting this loss with extra fertilizer and it would be less money and less work if he would just compost the sawdust. As far as that goes a heavy layer of lawn clippings can and will smother and stunt lawn gr as well.