Biodiesel fuel is made by distilling a plant oil until it is usable by an unmodified diesel engine. It is different from other forms of bio fuel because it works on existing engines, rather than requiring a specially modified engine, like ethanol 85 does. The major limiting factor on the commercial success of biodiesel is the fact that it only works with diesel engines, and not gasoline burning engines.
One of the chief challenges facing biodiesel fuel is solidification. You see, biodiesel starts to gel in the temperature range of 40-50 degrees. This means that in the US, in almost all 50 states biodiesel would clog the fuel lines if started cold at least some of the time. Thankfully, there is a solution to the problem.
A heating coil can be run through the biodiesel fuel tank that runs off of engine exhaust. The engine can be started using conventional diesel, and then an indicator light goes on when the biodiesel tank is warm enough to be used, and the driver can flip a switch to begin using that tank instead of normal fuel. It’s not a perfect solution to the problem, but it’s a great start in the right direction.