Biodiesel, dammit! Who cares who Prezza shagged?!
Here are some possible reasons:
1) Biodiesel is not as reliable as mineral diesel - it damages engines.
This is true, it can damage some engines, and needs to operate at a slightly higher temperature than mineral diesel. However, engines could easily be developed to run on biodiesel as efficiently as modern diesel engines take mineral diesel. If the oil companies and the car companies talk to each other a bit (it'd be a weird world if they aren't talking already about something), then it'd be an incredibly simple move to make, and with both organisations working together, it would provide a guaranteed return on the investments they made. Cameron would have a new biodiesel Lexus at the drop of a hat, and there are millions more like him.
2) There isn't the agricultural capacity to support the current oil usage with a vegetable-based alternative
So do some of it. Some is better than none.
3) No-one in important government positions, or in high-up places in car and oil companies gives a shit about anything that doesn't affect the time between now and the next election/their next annual bonus
I don't have a reply to this. Anyone?