Running a car on the energy flushed down the toilet

November 9th, 2010 by Wessex Water

Engineers have come up with a way of running vehicles in the UK on poo-power.

The Bio-Bug is believed to be the UK’s first VW Beetle that runs on methane gas generated from human waste.

The Bio-Bug runs on methane gas produced during the sewage treatment process (click image to expand)

Waste flushed down the toilets of just 70 homes is enough to power the Bio-Bug for year, based on an annual mileage of 10,000 miles.  About 550 cars could be powered by sewage from households in Guernsey based on each car driving 6000 miles per year.  More cars could be powered by methane from anaerobic digestion if food waste was used as well.

The green company behind the Bio-Bug said trials proved that ‘people-power’ could be used as an alternative fuel for their company vehicles.

Mohammed Saddiq, of sustainable firm GENeco, 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.

(click image to expand)

“The choice of car was inspired by students who took part in a workshop. They thought it would be appropriate that the poo-powered car should be the classic VW Beetle Bug because bugs naturally breakdown waste at sewage works to start the treatment process which goes on to produce the energy.

“At the moment we are using waste flushed down the toilets in homes in Bristol to power the Bio-Bug, but it won’t be long before the energy will also be generated through the treatment of food waste when we start recycling it at our sewage works.”

Countries including India and China use compressed natural gas (CNG) to power vehicles and a number of companies in the UK are now using CNG mainly to fuel buses and commercial vehicles. In Sweden, more than 11,500 vehicles already run on biomethane produced from sewage plants.

But using biogas from sewage sludge is yet to take off despite a significant amount being produced everyday at sewage plants around the country and it is sustainable.

GENeco, a Wessex Water-owned company, said it would produce significantly more gas at its Bristol sewage treatment works in Avonmouth through recycling food waste from homes and businesses in the south west.

It will mean both human waste and food waste could be used to power vehicles in the future.

Around 18 million cubic metres of biogas is produced at Bristol sewage treatment works a year.

It is generated through anaerobic digestion – a process in which bugs in the absence of oxygen break down biodegradable material to produce methane.

If all of the biogas produced at GENeco’s plant at Avonmouth was used to fuel vehicles it would avoid 19,000 tonnes of CO2 being put into the atmosphere.

Bath-based Greenfuel Company converted the Beetle so it could run on biogas while bosses from GENeco ran a workshop at a University of Bath event for teenagers from schools in Bath and North East Somerset to come up with ideas for the car’s design.

Mr Saddiq added: “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.”

“On first hearing of the Bio-Bug, some people will smile, and some people will go ‘yuck’!  Either way, what I hope they realise is that this is exactly the kind of innovation we now need for a more sustainable world – and those directly involved should be proud they’re making a small but significant contribution to it everyday.”

Jonathan Porritt, Founder Director, Forum for the Future

By generating renewable electricity from biogas GENeco is already contributing to the UK’s target of a 34% reduction in greenhouse gas emissions by 2020 and an 80% reduction by 2050.

If the company was to further convert biogas to compressed biomethane for use as a vehicle fuel a further contribution would be made to reducing greenhouse gas emissions.

Methane from anaerobic digestion of sewage and food waste can be used to power cars or heat or produce electricity for homes (click diagram to expand)

The Anaerobic Digestion and Biogas Association (ADBA) said the launch of the Bio-Bug proved that biomethane from sewage sludge could be used as an alternative fuel for vehicles.

ADBA chairman Lord Rupert Redesdale said: “This is a very exciting and forward-thinking project demonstrating the myriad benefits of anaerobic digestion (AD).

“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.”

ADBA chief executive Charlotte Morton added: “We are delighted to see such ingenuity and commitment to maximising the potential of AD from the water industry.”

GENeco said if the trial involving the Bio-Bug proved successful it would look to convert some of the company’s fleet of vehicles to run on biogas.

Interesting facts

  • Enough Biogas is produced at Avonmouth to send a car to the moon and back 119 times or around the world 2,287 times
  • The Bio-Bug does 5.3 miles per m3 of biogas
  • Waste flushed down the toilet of just 70 homes is enough to power the Bio-Bug for year based on an annual mileage of 10,000 miles
  • In Sweden more than 11,500 vehicles run on methane produced from sewage plants
  • To use biogas as vehicle fuel the gas needs to be treated – a process called biogas upgrading. It involves carbon dioxide being separated from the biogas
  • In the past methane hasn’t been “clean” enough which has meant it has affected the car performance
  • Bristol treatment works treats waste from around 1 million people living in Bristol, South Gloucestershire and North Somerset.

The Bio-Bug – an overview

  • Using biogas as a fuel for motor vehicles is very unusual in the UK.
  • Across many of the cities of mainland Europe, from Stockholm to Rome, from Reykjavik to Lille – biogas, from sewage and food waste, is an established and commonly used fuel in municipal buses and private cars.
  • Less tax, less noise and less pollution makes it a very attractive alternative to petrol and diesel.
  • GENeco’s Bio-Bug is a conventional 2 litre VW Beetle convertible which has been modified to operate with both petrol and compressed methane gas.
  • The car is started using petrol and when the engine is ‘up to temperature’ the system automatically switches to methane as its source of fuel.  Similarly when the methane tank is low on fuel the car will automatically revert back to petrol.
  • The conversion, carried out by the Greenfuel Company in Bath, takes the same time and is similar in cost to cars that are converted to the more conventional LPG.
  • The fuel for the Bio-Bug has been produced at Bristol sewage treatment works in Avonmouth and is stored in easy to handle cylinders.

(click image to expand)

Anaerobic digestion

  • Anaerobic digestion is a process in which microorganisms in the absence of oxygen break down biodegradable material to produce biomethane.
  • The environmental benefits of anaerobic digestion include:
  • Collection of methane providing a source of renewable energy that is carbon neutral, ie, providing energy with no net increase in atmospheric CO2.
  • The production of biosolids, which offer farmers a safe, sustainable source of nutrients that supply crop nutrients and enrich land with organic matter.
  • Reduction in the sludge volumes that have to leave the site.
  • Significantly lowers carbon footprint of the operating site.
  • Less smell than more conventional processes.
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