Go check out one of the "conversion kits" to get a good idea of what a "straight VO" system looks like. Like Greasecar Vegetable Fuel Systems

Basically how they work is this:

You have two tanks, one for the straight VO, and one for diesel. You start the engine on diesel. Once the engine is running, some method for heat is sent to the tank containing the VO to start heating it up. Most common is to use the radiator water lines run through a "coil" or some type of heat exchanger in the VO tank. Once the VO is heated enough (thin enough) to use, you switch over to the VO tank and run on that until it's time to shut down. Then you switch back over to the diesel tank to flush the fuel lines and injectors (you don't want VO sitting in those lines or injectors or it will gel). Then you shut down.

A commercially available conversion kit will usually have all the parts you need for the conversion, AND some will offer automation of the switching. The automated systems will monitor the temps and do the switching from one tank to another for you.

While I like the technical feasibility of it, here's my problem with a conversion kit. If you are technically inclined enough to build your own, then great. However, if you buy an off-the-shelf kit, they can be very pricy, almost the same price as an entry level bio-diesel processing system. So why not put the money in a bio-diesel processor and be able to use that fuel in any diesel vehicle, not just one vehicle that has a conversion kit?

Pros and cons both ways.

TX