Original URL: http://www.theregister.co.uk/2010/08/06/poo_car/

'Poo-powered' Volkswagen astounds world+dog

Gov-funded Dung Beetle runs on turds of seventy homes

By Lewis Page

Posted in Science, 6th August 2010 11:39 GMT

Updated The UK and green media is alive with reports of a "poo powered" car, dubbed the "Bio-Bug", developed to encourage sustainable motoring. But what's the real story?

The GENeco Bio-Bug CNG fuelled Beetle. Credit: Wessex Water

Plenty of grunt (etc).

"On first hearing of the Bio-Bug, some people will smile, and some people will go ‘yuck’!," comments former Friends of the Earth chief and Labour government eco-maven Jonathan Porritt*.

"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!"

In fact the Bio-Bug is simply a VW Beetle converted to run on Compressed Natural Gas (CNG), in other words mostly methane stored under pressure. It's more normal in Blighty to run vehicles on Liquefied Natural Gas (LNG), where the gas has been chilled into liquid form and thus doesn't require a heavy, bulky pressure vessel for storage. LNG is also denser, taking up less room. However CNG is easier to produce as no chilling/liquefaction stage is required. CNG is used to run some fleet vehicles here in Blighty, and in some countries is very popular as it is often a lot cheaper than petrol or diesel.

There isn't normally anything particularly green about running a vehicle on natural gas, which is after all a carbon-based fossil fuel. The difference here is that the CNG used to run the Bio-Bug is produced at Wessex Water's Avonmouth sewage plant.

Avonmouth already runs its "digesters" and other processing machinery using combined-heat-and-power plants running on poo biogas, and indeed generates a surplus of electricity which it sells to the National Grid. But it seems that there is still biogas left over after the plant's own requirements are met, which would otherwise simply be burned off as waste (venting it to atmosphere without burning would be a major eco-crime, as methane is a hugely more powerful greenhouse gas than CO2).

“With the surplus gas we had available we wanted to put it to good use in a sustainable and efficient way," says Mohammed Saddiq, general manager of Wessex Water subsidiary GENeco, which aims to monetise the company's sewage-derived products.

“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."

Why not just sell the gas? And why did the taxpayers have to cough up? And who cares? This is never going to be a big deal

This involved setting up some specialist machinery to "upgrade" the biogas to the point where it would run a CNG car properly - sewage gas contains quite a lot of CO2, which normally confines its use to specialised plant such as the Avonmouth CHP units. The taxpayer, as one might expect, was required to help with this through the medium of the South West regional development authority.

Only a limited amount of surplus biogas is available from Avonmouth now - GENeco says that it will convert "some of the company's fleet of vehicles" to run on bio-CNG if the Bio-Bug proves a success. However Saddiq thinks that larger supplies could come online once the firm starts processing food waste.

Biogas industry spokespeople were predictably overjoyed by the poo-powered car.

“Biomethane cars could be just as important as electric cars," insists Anaerobic Digestion and Biogas Association (ADBA) Chairman Lord Rupert Redesdale.

That would be great news if true, as biogas cars would be cheap and simple to make compared to electric ones. They wouldn't require special high-power charging points to be installed everywhere**, and they wouldn't require us to recycle megatons of worn-out batteries every year.

Unfortunately it isn't true, though - unless you add the caveat "assuming that electric cars remain insignificant". GENeco's engineers calculate that the Bio-Bug requires the poo of no less than 70 households to fuel itself. The average UK household at present operates at least one car and the nation also requires vast fleets of vans, buses, trucks etc: this means that even if all the nation's turds were used to make motor fuel no more than an insignificant, well-under-one-percent fraction of our vehicles could run on it.

In any case, all the nation's turds are not available for use as motor fuel: they are mostly required for powering the sewage plants as at Avonmouth. So actually, the potential contribution of poo-powered road transport to climate and energy-security issues is utterly, totally insignificant. This is not, no matter what Mr Porritt thinks, the kind of innovation we need for a more sustainable world - something a hell of a lot larger in scale is required.

In any case, one also has to wonder, if Wessex Water can produce nice CNG at Avonmouth, why it doesn't just sell it to the grid the way the company does its surplus 'leccy. You're allowed to do that if your gas has sufficient oomph, which presumably it does if it qualifies as CNG.

We have asked Wessex Water that, but we're still waiting for an answer. We'll update this as and when we hear back.

In the absence of a reply, though, one can't help wondering why we taxpayers had to cough up for the gas upgrading machinery so that GENeco can produce gas to run their vehicles and perhaps to sell for money.

Perhaps it simply wasn't worth Wessex Water's while unless the machinery was free. But given that this sort of thing is never going to make much impact on the nation's green/energy problems, it's hard to see why it was worth the taxpayers' while either. ®

Updated to add

Wessex Water have been back in touch to say:

"We are aware of two projects seeking to inject biogas into the transmission grid. Depending on their success, we may move in that direction ourselves in future."

Bootnotes

*Porritt is a standard hard-green type: intensely anti-nuclear, against economic growth, considers solar power worthwhile in the UK climate etc. He was brought into government in the Blair era to be a "critical friend" as head of the Sustainable Development Commission, a post from which he resigned last year.

**Electric cars can be charged up from ordinary wall sockets, but you really don't want to. The Tesla Roadster, for instance, takes 48 hours to charge up from a standard US wall socket. Don't use it to go for overnight visits!