It doesn't have to be cow manure for the anaerobic digesters - it could be human. There are far more humans than cows (here in London, anyway) and we already have the collection facilites - sewers and sewage works. Just convert the sewage works to turn the brown stuff to methane and Bob's your mother's brother.

Using the methane in vehicles like LPG/LNG (LSG?) is more efficient than converting it directly or indirectly to Hydrogen. (LNG ships bringing methane/natural gas from the middle east burn the boiled off gas in their diesels, so its hardly new technology)

This has several advantages:

- the CO2 given off would have been anyway so no net gain

- the methane is captured instead of adding to the greenhouse effect.

- the waste product is an odourless compost that can be used to improve arable land (for growing biofuel crops!)

- Less waste to be poured into the rivers and seas.

- there are far more existing filing stations with facilities for handling LPG than hydrogen.

You could even brew your own : Me-Thane™ to use in your "Bog-standard" <groan> car, otherwise fill up at pump number 2!

Sorry if this all sounds a little faecesious <sic>

Mines the brown-stained orange overalls and waist-high waders.