With all the talk about global food shortages, why haven't we turned our attention to grass? After all, grass is edible, is the food source for many of the animals that we eat, and most convenient of all, these greens are right in our own backyard.
However, although grass is indeed safe to eat, it is not a practical food source at least for humans. Our stomachs are not evolved to efficiently digest the raw grass, which is high in cellulose. Cows that can't get enough of grass, on the other hand, have specialized stomachs with four chambers and a gut microbiome that helps them break down the grass.
Grass also has a high silica content (surprisingly). This is why teeth of grazing animals are mostly flat and grow continually. By contrast, chewing on grass would eventually wear down human teeth, which are only replaced once.