Use hemp oil. It is fully generated from hemp seeds and needs NO modifications on diesel cars. Just use it as you would use conventional diesel fuel.
You can also mix it freely with conventional diesel fuel.
Its non-toxic, easy to produce, CHEAP and very RELIABLE (more reliable than the middle east oil). Remember, hemp could also replace cotton or ANY organic fiber material thats in currently use, including wood, so the other remaining plant parts would have significant uses. Oh and it produces more fiber/acre than any other plant in the world. Before 1930 sudden global ban it was the worlds most used plant everywhere. Guess where textile name "Canvas" originates?