About grass being extra grain for food or feed...I let the wild sunflowers grow up wherever the want. When the flower heads are dead I snip off a few because all those tiny sunflower seed are free chicken feed. I'd eat them to in a pinch. When I pull out the plants I give the whole thing to the chickens. And let them pick off what they want.
Sunflowers can also be used for oil for cooking and even biofuel - such a useful plant. Everyone seems to overlook it :(
How would you extract the oil? I think the gadgets I've seen are too much trouble.
Well considering that sunflower oil is available on every shelf... I would say find out how the companies do it and create a smaller version. Pressing is probably the best way, although you b could grind the oil out with a DIY millstone that collects the oil.