Where there's muck there's eco-friendly fuel

Contrary to toilet humour, more methane is emitted from the front of a cow than the rear: like an uncle who's had too much to drink at Christmas, burping is the main culprit, writes Nathan Rous.

Yet it is the 'business end' of a cow which is attracting all the attention. Call it a trump card in the fight against climate change.

Ken Livingstone wants it for London, Environment Secretary Hilary Benn is throwing money at it and Adam and Debbie are bringing it to Ambridge.

Naturally controversial (in the same respect that anything different from the norm seems to get the protesters out of the woodwork) anaerobic digestion could soon be all the rage.

Simply, anaerobic digestion is when organic material is broken down by micro-organisms in the absence of oxygen: the same process used in septic tanks.

The reason farmers are rubbing their hands with glee is because not only does it treat their waste products (mainly manure and slurry) in a more efficient way, it also produces valuable by-products.

As the organic matter degrades, it gives off biogas - a mixture mainly of methane and carbon dioxide (CO2). This is similar to natural gas and can be burned to generate heat and electricity, which can be fed to the national grid or used locally. There is also a liquid residue and a solid residue, both rich in nutrients, which can be used as a fertiliser and soil conditioner.

The very fact that it generates heat and power without directly using fossil fuels should reduce CO2 emissions and allow farmers to become more self-sufficient in energy.

Of course, there's the small matter of digesters costing £400,000 a pop. Despite the promise of funding, few will investigate further if that promise fails to materialise.

As a biogas, methane is far less environmentally damaging since the CO2 it gives off is immediately reabsorbed by plants. And it is already being used in projects around the globe to generate electricity while attracting increasing interest from the car industry as a source of renewable energy.

Of course, trust our European friends to take it that one stage further. Given that no viable method has been devised to capture this gas as it erupts from either end of the cow, Swedish company Svenska Biogas is doing the next best thing: taking the bits of cows that would otherwise be discarded during the slaughter process - stomach and intestines primarily, but also udders, blood and parts of the liver and kidneys - and extracting the residual methane directly from them.

The digestive tracts of all living creatures produce methane, a by-product of the action of bacteria breaking down ingested food matter. Because cows have four stomachs, they create considerably more of the gas than any other animal - 75 per cent of the total methane produced by all animals.

"Depending on the cow's size, we can get 80-100 kilos of material from each animal," says Carl Lilliehook, managing director of Svenska Biogas.

"These are all the things that would otherwise be classified as food-process waste and either incinerated or disposed of in landfill sites.

"This material is then heated at 70 degrees centigrade for one hour to boil off the impurities, and put in a digester for one month, where micro-organisms break it down, producing a mixture of methane and CO2 which is drawn out of the top of the digester."

For the first time in my life I can smell the winds of change.