I should assume you've never been there...
You MAY be able to find something around Page. Otherwise the only gas is available at Jacob Lake (expensive gas, great pies in the restaurant) or at a little shop halfway between Jacob Lake and the park entrance (more expensive, no pie). I don't know about diesel at all, though I expect that it's available for the RV crowd and maybe some park service vehicles. At these two places there is no town, just cabins for the gas station staff, and they close in the winter due to excessive snow (the other reason I doubt biodiesel is there).
I don't know that BD is available in AZ outside of Phoenix/Tucson at all.