You'll want to leave the grass-clippings in the lawn for fertilisation. Sure, you could add fertilizers, but then why not just give the lawn bot a place to plug-in (like a Roomba) instead? It's easier and I'm pretty sure it's cheaper, also.

Also, I'm not sure the world is ready for autonomous robots with blades. Imagine it foraging onto the neighbouring lawn, prompting the interest of a 4-year old... ugh.