BioDieselNow - Renewable biodiesel fuel

Can anybody tell me what the difference between the oil that is pressed out of the seed directly from the press and the cooking oil you would buy in the bottle at the supermarket? Is there further processing and what is it?

Huh, so that's what Horchata is made from - From http://en.wikipedia.org/wiki/Cyperus_esculentus : "Since the tubers contain 20-36% oil, C. esculentus has been suggested as potential oil crop for the production of biodiesel . [3] ." Wiki appears to be talking about a specific variety of the plant, which...