Where there’s muck there’s gas

It might be poo to you, but to British Gas sewage is a source of low carbon fuel people can use for cooking and heating in their homes.

The company has teamed up with Thames Water and Scotia Gas Networks on a joint venture project to supply up to 200 homes with so-called bio-methane. The gas is exactly the same as conventional natural gas, but because it is derived from renewable rather than fossil sources, it helps to ‘decarbonise’ the gas grid.

“At British Gas, we’re already leading the way with low carbon and renewable technologies for Britain’s homes, and now we’re helping local communities use local resources to generate their own energy. This renewable gas project is a real milestone in Britain’s energy history, and will help customers and the environment alike,” said Gearóid Lane, managing director of Communities & New Energy at British Gas.

“Renewable gas has the potential to make a significant contribution to meeting the UK’s energy needs. Gas from sewage is just one part of a bigger project, which will see us using brewery and food waste and farm slurry to generate gas to heat our British Gas homes.”

Enough bio-methane is being generated at Didcot sewage works in Oxfordshire to supply up to 200 homes in this pilot project, which is hoped to become the first of many. By 2020, according to a study by National Grid, bio-gas could account for 15 per cent of the domestic gas market – supplied via the existing gas grid and needing no upgrades to existing gas burning installations in the home.

“It’s not every day that a Secretary of State can announce that, for the first time ever in the UK, people can cook and heat their homes with gas generated from sewage,” said the energy and climate change secretary Chris Huhne.

“This is an historic day for the companies involved, for energy from waste technologies, and for progress to increase the amount of renewable energy in the UK. I know there are other similar projects across the country that are close to completion, so this is just the start of a new era of renewable area.”

Sewage arrives at the Didcot works from some of Thames Water’s 14 million customers to be trated and recycled back to the environment. Sludge, the solid waste left over from the treatment of raw sewage, is then subjected to further treatment called anaerobic digestion. This takes in place in warmed-up vats where bacteria breakdown organic material, yielding methane as a by-product. Any impurities in the gas are removed before the methane is pumped into the gas grid.

From flushing the toilet to igniting an oven hob burning the bio-fuel takes around 20 days.

“We already produce £15 million a year of electricity by burning bio-gas from the 2.8 billion litres a day of sewage produced by our 14 million customers,” said Martin Baggs, Thames Water’s chief executive. “Feeding this renewable gas directly into the gas grid is the logical next step in our ‘energy from waste’ business.

“What we have jointly achieved at Didcot is a sign of what is to come, which can be replicated across our network and indeed the whole country. Every sewage works in Britain is a potential source of local renewable gas waiting to be put to use.”

John Morea, chief executive of Scotia Gas Networks added: “Just as Thames Water has to clean sewage waste, we have to clean the gas to ensure it’s fit for purpose to pump into our network. The gas we are transporting from Didcot doesn’t arrive from the North Sea or abroad, but instead comes from the homes we are delivering the gas to. That’s got to be recycling at it’s very best.”
One might say that what goes around, come around.

Shooting the breeze with some bio-gas facts

The average person produces 30 kilogrammes of dried out sewage sludge per year that can be used to generate bio-methane

That means the UK’s 62.5 million people could in theory generate enough renewable gas to meet the annual demand of 200,000 homes – up to one per cent of the UK’s population

That’s because if all 9,600 sewage treatment works in the UK were fitted with the technology, they could generate sufficient gas for all those 200,000 homes, though in practice it would be unrealistic to fit the technology to every treatment facility.