Nelson started the company back in 2004 when he first got interested in biofuels (due to his wife owning a diesel car that she fueled with biodiesel).
BioWillie helps local farmers by turning their crops into fuel for American truck drivers. So biodiesel is meant to fuel your truck, not your mobility scooter which are also nice vehicles and good fun if you are old or too lazy to walk like me.
If you want to learn more about the basics of biodiesel then refer to this article on Alternative fuels data center.
You can follow BioWillie on twitter here.