Bio Diesel is modified cooking oil. Basically, oil is 'cracked' using a mixture of methanol and lye, yielding 3 energy chains and one molecule of glycerin from each molecule of oil. It is a much better lubricant than diesel so needs no sulfur added to it. BD does have a higher gel point than diesel, so in winter is usually blended. The only vehicle 'conversion' necessary is to check the fuel line rubber type, and add a secondary filter as BD is a better solvent than diesel and at first will dissolve the sludge in your fuel tank. More info:
http://www.biodiesel.org/