Fatbergs clogging up sewers could provide homes with green energy: New technique to break down solid masses of fat, oil and grease into natural gas is developed by scientists
- Fatbergs are made up of flushed waste and can block sewers beneath cities
- Heating fatbergs up and adding a certain chemical can quickly break them down
- This new technique turn the solid masses into a source of renewable energy
Fatbergs clogging up sewers beneath cities across the globe could soon provide 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 resulting sludge can be treated to release methane gas, a renewable energy source that can be used to drive a turbine to generate power.
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Fatbergs clogging up sewers in Britain’s cities could soon provide homes with green energy. A technique to break down the solid masses of fats, oil grease (FOG) has been developed. The treatment (centre and right) broke down 80 per cent of solids in FOG samples (left)
The new method could offer a use for pesky fatbergs – flushed waste that can grow to enormous sizes in the sewers beneath bustling cities.
Last year, a 130-ton, 250-metre-long (820ft) fatberg blocked up a Victorian tunnel in Whitechapel, east London. It took three weeks to clear.
The mixture of fats, oil and grease, known collectively as FOG, could be heated to break them down, researchers at the University of British Columbia found.
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They heated clumps of FOG to temperatures between 90 and 110 degrees centigrade (194F-230F).
Adding hydrogen peroxide, a chemical that kick-starts the breakdown of organic matter.
Researchers said the treatment dramatically reduced the volume of solids in the FOG by as much as 80 per cent.
The technique could offer a use for pesky fatbergs – flushed waste that can grow to enormous sizes. Last year, a 130-ton, 250-metre-long (820ft) fatberg blocked up a Victorian tunnel in Whitechapel, east London (pictured). It took three weeks to clear
The mixture of fats, oil and grease, known collectively as FOG, that makes up fatbergs could be heated to break them down, researchers at the University of British Columbia found
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 said: ‘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.
WHAT ARE FATBERGS?
Fatbergs are blockages made up of flushed fat, oil, grease and other flushed waste such as wet wipes and illegal drugs.
They 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 was a 750-metre (2,460ft) monster found under London’s South Bank in 2017 (pictured)
They can grow metres tall and hundreds of metres long, with water providers last year declaring an epidemic of fatberg emergencies in 23 UK cities, costing tens of millions of pounds to remove.
The biggest ever discovered in the UK was a 750-metre (2,460ft) monster found under London’s South Bank in 2017.
Fatbergs take weeks to remove and form when people put things they shouldn’t down sinks and toilets.
‘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 could enable farmers to load more FOG into their biogas digesters – large tanks that treat farm wastes, including cow manure.
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.’
HOW MUCH DO ‘FATBERGS’ COST THE PUBLIC?
Fatbergs – congealed fat which clumps together with other waste products to form concrete-style blocks – are becoming increasingly problematic in sewers across the UK, particularly in London.
The capital’s largest ever recorded fatberg, weighing in at 15 tonnes, was found in Kingston in August 2013.
And in 2015 workers spent four days removing a fatberg the length of a jumbo jet from a sewer in Shepherd’s Bush.
In Bedfordshire a line of fatbergs clogged a 100-metre-long pipeline in 2016. Anglian Water had to ship in a specialist robot (pictured) with a high-pressured jet from Holland to blast the fatbergs so they would gradually disperse
Among the most common causes of drain blockages are make-up and nappy wipes, fat and grease, chewing gum, dental floss, plasters and building debris.
Staff from Thames Water usually use powerful suction equipment to break down the blockages and then high-powered water jets to clear the tunnels.
The company spends approximately £1 million a month clearing fatbergs and blockages, dealing with 55,000 of them every year. It is a similar story for other water companies across the UK.
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.’
The study was published in the journal Water, Air, & Soil Pollution.
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