Germany seems to be ahead in methane/biogas fuelled cars.. with over 400,000 in use. The cars are dual fuel as in being able to run on methane and petrol giving a range of about 450 miles on one 'tank'.

.. the waste from 70 households in enough to provide enough fuel for 10,000 miles.

From a UK article..

To use biogas as vehicle fuel without affecting vehicle performance or reliability the gas needs to be treated to remove the carbon dioxide content. GENeco, part of Wessex Water, imported specialist "cleaning" equipment to treat the raw methane generated at the sewage treatment works in Avonmouth.

The spokesman added: Our site has been producing biogas for many years which we use to generate electricity to power the site and export to the National Grid. "With the surplus gas we had available we wanted to put it to good use in a sustainable and efficient way.

"We decided to power a vehicle on the gas offering a sustainable alternative to using fossil fuels which we so heavily rely on in the UK."