Your point illustrates the beauty of Saphire's plan. Their end product is chemicaly / molecularly exactly the same as gasoline... no need for the biodiesel tag.... Simply gasoline... never mind the source of the refined end product.
The problem is cost. It is still outrageously expensive for them to produce the end product. Something like 250 bucks a barrel. BEHL claims cheap / impressive numbers for 'biodiesel', but until they produce a gallon of certified fuel and document the cost it does not mean a damn thing.
And they know this. That is why they are focusing on human and animal feedstock. The profit margin there is great !!!