hello,
As far as the bus goes, you should visit "thedieslstop.com, that is the ultimite forum for bio-diesl vehicles.(of course that is my oppinion anyway). For heating, if your budget is limited, you may consider a multifuel boiler. There are many boilers out there that have an oil burner at one end and a wood or coal burner on the other end. You could substitute the oil burner for a gas burner if you wanted to, but since you are on a low budget you may try to run wvo or used motor oil on the oil burner side. From my experiance, the waste motor oil units produce a long flame and require a deep firebox to accomodate it. Most of your average multifuel units are designed specifically for #2 oil and are quite compact. If I have time this fall or winter I may try to modify my oil burner with a longer delivery tube or even extend the combustion chamber of my multifuel boiler to accomodate a homebuilt wvo or wmo burner. I am sure it can be done with little creative effort, however if this is for a school you may have some liability concerns so be carefull. Just remember, if it was easy everyone would be doing it. This forum is a great source of information, be it experimental or tried and true, keep on researching, it is a learning thing, school or no school, it's all about learning.
Mike