Dave HarveyBusiness and environment correspondent, West of England
BBC
Dairy farmer Richard Clothier sees cow manure as “nature’s crude oil”
How many homes could be heated by cow muck?
It is not a question I have thought about before, but as Britain searches for sustainable sources of heat, many farmers are looking, well, right under their noses.
Cow manure can be treated to release biomethane, a renewable gas which is already used to power central heating boilers in about a million homes.
But there is “huge potential” to increase that to 15 million homes, according to the campaign group Green Gas Taskforce.
One dairy farmer who turns his cattle waste into biomethane, describes cow muck as “nature’s crude oil”.
So how do you turn cow poo into gas? Could we really make that much of it? And is it as green as they claim?
Somerset dairy farmer Richard Clothier loves cow manure. In a cattle shed on the Somerset hills, near Bruton, we are scraping it off the floors with old fashioned shovels. The job is usually done by a robot these days, but the farmer is happy to do what many would call a dirty job.
“This is nature’s crude oil for us,” he says. “This is highly calorific waste for generating gas.”
Mr Clothier’s family have been farming cattle for two centuries, and have always realised the power in manure. In 2013 they built a £4m plant to extract the methane from their cows’ waste.
The £4m biogas plant extracts enough methane from farm waste to heat 10,000 homes
The manure is collected in huge tanks and pumped into an anaerobic digester (AD), where bacteria break down the organic material.
Mr Clothier explains: “The methanogenic bacteria are gobbling up all the solids and generating loads of lovely methane, which we then catch in the hoods over the top.”
The gas is then cleaned and carefully regulated before being injected into the national gas grid.
Some is used directly to run the cheesemaking dairy for Wyke Farms, Mr Clothier’s family business.
“We make 100% of our own energy”, he says. “Which is great for the planet, and for our business.”
So how many homes can be heated with the gas from Wyke’s cows? In total, Mr Clothier calculates, 10,000 homes a year.
How much manure becomes gas?
Hardly any. British cows produce about 90 million tonnes of slurry every year, but only 2.5% of it is fed into AD plants.
Despite the obvious benefits of free energy and even selling surplus power to the grid, the installation costs are high.
So now a campaign is under way to get more gas produced this way.
Nether Stowey celebrated ten years of using biomethane to heat the Somerset village
In the little village of Nether Stowey, nestled in the Quantock hills, a birthday party was under way in the village hall.
It is an unusual cake, for a quirky celebration. The village’s gas plant has turned 10, so locals made a cake shaped like the two domed gas tanks.
The primary school children who came to the party have been raised almost entirely on gas from the nearby plant.
This one is not fed with cattle manure, but human food waste. This is collected by local councils and fed into a digester, and once again the bacteria get to work.
The cake is part of a campaign. Wales and West Utilities run the national gas grid in Somerset, and the company is keen to get more biomethane produced.
Already the West Country is a “hotbed for anaerobic digestion and biogas”, according to Matt Hindle, head of Net Zero at Wales and West.
There are 20 biomethane plants in the south-west of England, but the firm wants more.
“We think biomethane could be a really significant part of our gas mix and could work with hydrogen, and electrification, as part of a whole system approach to decarbonisation of the heating system,” said Mr Hindle.
How much biogas could be made?
Ten times as much, or even more, according to the campaign.
Clearly not all cow muck can be harvested. But if more food waste was collected, and more biogas plants built near dairy farms, “by 2050, we could be looking at 10-15 million households heated with biomethane”, said Charles McAllister, director of the Green Gas Taskforce.
Mr McAllister believes biomethane could heat 10 million homes by 2050
The taskforce argues building more biogas plants near farms will spread the economic benefits of renewable energy to rural areas.
Mr McAllister said: “It means investment in rural communities, jobs in rural communities, not in the big cities, while decarbonising the energy we use and improving the local environment.”
But even if the industry grows tenfold, it will reach a natural limit.
There is, ultimately, only so much cow muck to feed the system.
And that is where green campaigners worry that biogas will not be as green as it claims.
Green gas or ‘greenwash’?
Making gas out of cow muck is widely agreed to be a win for the planet. Capturing the methane in manure and putting it to controlled use is better than allowing it to evaporate, worsening climate change.
But biogas is also made from other sources already, like crops grown for fuel not food. And environmentalists worry the rest of the gas in the pipelines will continue to come from fossil fuels, instead of being replaced by renewable electric power.
Energy analysts at think tank Regen estimate that at best biomethane could replace 18% of total UK gas consumption.
Tamsyn Lonsdale-Smith, the analyst who wrote the report, said the potential of biomethane can be overstated.
She said: “Even 18% is an optimistic scenario, so we do need to find other ways to decarbonise heating and transport.”
Back in his cattle sheds, Mr Clothier is sure of one thing. For dairy farmers like him, harnessing the natural power of his cow’s daily waste is a no-brainer.
He said: “There’s so much farm waste that could go into plants like this and generate loads of methane and save energy that otherwise the UK has to buy into the country.”
