full tank

In Six Degrees*, Mark Lynas quotes Jeffrey Dukes' calculation that an average US gallon of gasoline requires:

'approximately 90 tonnes of precursor plant material in the process of its formation in ancient oceans (think of that every time you fill your tank).'

So, if you drive from London to the Edinburgh Fringe this year, and most British actors live in London (it's the voice-overs), you will get through about 1,350 tonnes of precursor plant material each way.

*p260