THE fatbergs are coming. These huge lumps of cooking oil and wet wipes lurk beneath UK streets, threatening to block sewers and put everyone off their lunch.
And they really are huge. In 2017, a monstrous 250-metre-long fatberg that weighed 130 tonnes was found under Whitechapel in east London – a piece of it still . In 2018, another rivalling it in size was found south of the river Thames and later analysed on a TV programme called , while in December that year, a whopping 800 tonnes of fat were removed from sewers in Cardiff. Even a relatively modest , made national headlines last month. So is this a new problem, or do Brits just have a new-found love of talking about it?
The word “fatberg” was coined in 2008, but only when utility firm Thames Water discovered a 15-tonne blockage in London’s sewers. By 2017, the portmanteau had been added to the Oxford English Dictionary, so clearly it has caught people’s imaginations.
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Tom Curran of University College Dublin, Ireland, says there has been a rise in the number of fatbergs and various factors have contributed to it: growing urban populations, ageing sewers, a rise in eating out and our increased flushing of wet wipes.
“A 250-metre-long fatberg was found under east London – a piece of it still resides in a museum”
Fatbergs are masses of fat, grease and oil congealed around wet wipes and other things that people shouldn’t flush down the toilet, like cotton buds and tampons. A found that, out of the solid items that could be identified, 93 per cent of the material recovered from sewer blockages were non-flushable wipes. Clearing the UK’s 300,000 annual sewer blockages costs £100 million, it says.
Plenty of other items have been found inside fatbergs too: condoms and chocolate bar wrappers were spotted in parts of the Whitechapel monster.
This mass of solid material is a problem, but as the name “fatberg” suggests, fat plays an important role in creating blockages. Cooking oil from a pan, excess gravy tipped down the sink and salad dressing rinsed off a plate all contain fats that end up in wastewater pipes.
Both commercial and domestic kitchens are culpable, but restaurants take the lion’s share of the blame because they prepare more meals and use more cooking oil than individual homes. It isn’t just places that prepare hot food: baristas who swill away coffee grounds and milk are also feeding fatbergs, says Raffaella Villa of Cranfield University, UK, who was part of the team that analysed the Whitechapel one.
We used to think that fat congealing as it cools was the main contributor to fatbergs, but a found that a key step is the saponification – turning into soap – of fats. Fats washed down the drain break into fatty acids, and those combine with calcium in the water to create hard, water-insoluble, soap-like deposits. These deposits build up around the sides of a sewer, like plaque builds up in arteries, and trap wet wipes as they grow, until you get a fatberg.
Clean-up operation
So we have an idea of how fatbergs form – but is there a reason they have drawn most attention in the UK? Blockages occur in sewers beneath towns and cities around the world, with notable fatbergs in , and in , yet the UK does seem to have cultivated a reputation for creating giant ones. “London has larger Victorian sewers, which lend themselves to larger fatbergs more likely to get high profile media attention,” says Michael Benke from Thames Water.
Curran says there is another factor that might be contributing to the giant fatbergs forming in UK sewers: letting food outlets off the hook.
The , which governs the nation’s sewers, doesn’t explicitly mention fats, but it does say that you shouldn’t pour away “any matter likely to injure the sewer or drain, to interfere with the free flow of its contents”. UK building regulations also state that commercial hot food kitchens .
“The wording of legislation is not as clear-cut as it is in other places around the world,” says Curran. For example, Dublin requires that waste water from restaurants doesn’t exceed a fat, oil and grease content of 100 milligrams per litre. Specific targets make it easier to enforce the rules, he says. “There tends to be a softly-softly approach with following up with restaurants.”
The Dublin example shows how to fight the fatbergs. Before 2008, the city had about 1000 sewer blockages every year. That year, it began requiring food outlets to hold waste-water licences and started a programme of inspections, sampling waste water and promoting the importance of not pouring fat out into the sewers. Since then, the number of blockages has gone down to fewer than 100 per year.
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Doing the same in the UK might not be so straightforward. UK water companies are privately owned and don’t have the power to inspect restaurants themselves, only local councils do, says Villa.
It is clear the problem needs fixing, though. Villa ran a survey of 103 restaurants in the UK towns of Reading and Bedford and found that 70 per cent had no grease management in place. “The restaurants understand that fats are the cause of fatbergs, but they don’t understand that they are causing the problem,” she says.
Addressing this misconception is essential, because once fatbergs are in the sewers, removing them is tricky. It tends to involve high-pressure water jets and weeks of manual labour to break them into smaller parts that can be taken away.
“Restaurants understand that fats cause fatbergs, but don’t get that they are causing the problem”
A better solution would be to monitor the sewers before fatbergs arise. Curran is working on using low-cost sensors to provide an early-warning system for fatberg formation. Ultrasonic sensors, for example, could monitor the sewage level in the pipes. If the level starts rising, that could indicate a blockage downstream. And a company called Nuron is putting fibre-optic cables through sewers to both deliver broadband and act as pressure and temperature sensors to monitor the sewer conditions in real time.
For its part, Thames Water is focusing on educational campaigns, both for households and for businesses, to stop people contributing to fatbergs. Its “Bin it – don’t block it” campaign, launched in 2013, encourages people to flush only “the three Ps” – pee, poo and toilet paper – and to collect cooking oil in a container that can be put in the bin, rather than down the sink.
There are signs that it is working: the number of blockages the water company has to deal with is on the decline, from 85,000 per year when the campaign started, to 75,000 in 2019. “The number is gradually falling, but it is still a massive problem,” says Benke.
Meanwhile, for those who can’t bring themselves to bin wet wipes, Water UK launched a “fine-to-flush” label identifying products that will break down quickly after flushing.
Curran has first-hand experience of how problematic wet wipes can be. Before he began researching fatbergs, when his children were small, he fell prey to a brand of “flushable” wipes – and just weeks later, the sewer outside his house was blocked. “You can flush a lot of things down the toilet,” he says, “but it has consequences.”
