The Bio-Bug has been converted by a team of British engineers to be powered by biogas, which is produced from human waste at sewage works across the country.
They believe the car is a viable alternative to electric vehicles.
Excrement flushed down the lavatories of just 70 homes is enough to power the car for 10,000 miles – the equivalent of one average motoring year.
This conversion technology has been used in the past but the Bio-Bug is Britain’s first car to run on methane gas without its performance being reduced.
It can power a conventional two litre VW Beetle convertible to 114mph.
Mohammed Saddiq, of sustainable energy firm GENeco, which developed the prototype, claimed that drivers “won’t know the difference”.
He said: “Previously the gas hasn’t been clean enough to fuel motor vehicles without it affecting performance.
“However, through using the latest technology our Bio-Bug drives like any conventional car and what’s more it uses sustainable fuel.
“If you were to drive the car you wouldn’t know it was powered by biogas as it performs just like any conventional car. It is probably the most sustainable car around.”
The Bio-Bug is a conventional 2 litre VW Beetle convertible, which has been modified to run on both conventional fuel and compressed methane gas.
The car is started using unleaded petrol but automatically switches to methane when the engine is “up to temperature”.
If the methane tank runs out the Bio-Bug reverts back to petrol.
Around 18 million cubic metres of biogas is produced from human waste every year at Wessex Water’s sewage treatment works in Avonmouth, Bristol.
The gas is generated through anaerobic digestion – where bugs which are starved of oxygen break down biodegradable material to produce methane.
However, before the gas can be used to power vehicles it must undergo “biogas upgrading” where carbon dioxide is removed to improve performance.
The Bio-Bug does 5.3 miles per cubic metre of biogas, which means that just one sewage works could power 95,400,000 miles per year saving 19,000 tonnes of CO2.
Lord Rupert Redesdale, chairman of The Anaerobic Digestion and Biogas Association, believes that the Bio-Bug could prove to be the future of green motoring.
He said: “This is a very exciting and forward-thinking project demonstrating the myriad benefits of anaerobic digestion.
“Biomethane cars could be just as important as electric cars, and the water regulator Ofwat should promote the generation of as much biogas as possible through sewage works in the fight against climate change.”
GENeco, which is a sustainable energy company owned by Wessex Water, plans to convert its fleet of vehicles if the Bio-Bug trial proves to be successful.
The Bio-Bug emits three tonnes of carbon dioxide in an average year whilst a conventional vehicle emits 3.5 tonnes.
However, the Bio-Bug is carbon neutral because all of its CO2 would have been released into the atmosphere anyway in the form of methane gas.
Conventional vehicles use fossil fuels, a non-renewable, finite source of energy, and the CO2 they emit would not otherwise have been released into the atmosphere.