Fatbergs clogging up sewers in Britain’s cities could soon be providing homes with green energy, according to new research.
A technique to break down the solid masses of congealed fat, wet wipes, nappies, oil and condoms has been developed by scientists.
The flushed waste can grow into fatbergs like the 130 ton monster and 250 metres long that blocked up a Victorian tunnel in Whitechapel, east London, a year ago.
Earlier this year a Channel 4 documentary unveiled another three times as long – under the capital’s South Bank.
But the fats, oil and grease, known collectively as FOG, threatening public health have now been found to have a potential environmental use by being turned into green biogas methane.
In experiments, the Canadian team heated them to temperatures between 90 and 110 degrees centigrade.
Adding hydrogen peroxide, a chemical that kickstarts the breakdown of organic matter, then reduced the volume of solids by up to 80 per cent.
It also released fatty acids from the mixture that can be broken down by bacteria in the next stage of treatment.
Engineer Dr Asha Srinivasan, of the University of British Columbia, explained: “FOG is a terrific source of organic material that microorganisms can feed on to produce methane gas, which is a valuable, renewable energy source.
“But if it is too rich in organics, bacteria cannot handle it and the process breaks down.
“By preheating it to the right temperature, we ensure that the FOG is ready for the final treatment and can make the maximum amount of methane.”
Her team’s method will enable farmers to load more FOG into their biogas digesters – the large tanks that treat farm wastes, including cow manure, to produce methane.
Dr Srinivasan said: “Farmers typically restrict FOG to less than 30 per cent of the overall feed.
“But now the FOG can be broken down into simpler forms, so you can use much more than that, up to 75 per cent of the overall feed.
“You would recycle more oil waste and produce more methane at the same time.”
Lead researcher Professor Victor Lo said, ultimately, the technology can be used in municipal FOG management programmes.
He added: “The principle would be the same. You pretreat the FOG so it doesn’t clog the pipes, and add it to sewage sludge to produce methane from the mix.
“To the best of our knowledge, this type of pretreatment for FOG has not been studied before, although simple chemical methods do exist to break down FOG.
“We are hoping to do more research to find the optimal ratio of FOG to dairy manure so they can be pretreated together.”
Fatbergs form into huge concrete-like slabs and can be found beneath almost every UK city, growing larger with every flush.
They also include food wrappers and human waste, blocking tunnels – and raising the risk of sewage flooding into homes.
The biggest ever discovered in the UK featured in Channel 4’s Fatberg Autopsy: Secrets of the Sewers, when cameras followed a team of eight ‘flushers’ as they chipped away at the 750 metre whopper under the Southbank.
The one discovered beneath Whitechapel last September was longer than Tower Bridge – and weighed as much as 11 double-decker buses.
Fatbergs take weeks to remove and form when people put things they shouldn’t down sinks and toilets.
The study was published in the journal Water, Air, & Soil Pollution.
By Ben Gelblum and Mark Waghorn
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