National Geographic Daily News
Fat blocks a sewer.

A large block of fat called a fatberg found inside a London sewer.

Photograph courtesy Thames Water

Daniel Stone

National Geographic

Published August 7, 2013

The name alone was enough to make us want to see for ourselves. Fatbergs, the giant collections of grease, oil, and fat that clog the sewer system under London's streets, were getting out of hand, the result of decades of people washing things down their drains that they're not supposed to. It all ends up in the tunnels, along with the other usual things that run through raw sewage tunnels.

When I toured London's sewers earlier this year with National Geographic video producer Spencer Millsap, what we found was a potent cocktail of smells. Fungus covered every surface of the tunnels. The humidity was so great that our camera's lens instantly fogged up. Running around our feet was a shallow river colored an earthy, brown hue (exactly why you think).

But the fatbergs were the main attraction, the bobbing piles of gunk that simply refused to be washed downstream and were slowly stopping up the sewer system. (See "Pictures: Walls of Fat Clog London Sewers.")

The smells instantly rushed back this week when London's water authority announced that it had discovered the biggest fatberg yet, a 15-ton mound about the size of a school bus. Thames Water, the public utility that manages the sewers, gave it the historic and oddly momentous title of being "the biggest berg in British history."

Unimpressed were dozens of nearby residents, who complained to the sewer authority that they couldn't flush their toilets—the fat had reduced a pipe nearly two feet (0.6 meter) in diameter to only five percent of its normal capacity. When sewer workers—well-paid ones, as all sewer workers are in London—went to investigate, they found the blockage.

The process of removing the fat, they later realized, would take more than a month.



London Sewers from National Geographic Magazine on Vimeo.

"Clean" Energy?

Despite the disgust, as well as the inconvenience, there's actually some good news about fatbergs. Made of dense fats and oils, the structures are highly caloric, which makes them helpful for producing energy.

Rob Smith, a man with the enviable title of London's "chief flusher," told us that simply removing the fat and burning it in a turbine can produce more than 130 gigawatt-hours of energy each year, or about enough to power 40,000 London homes. The city plans to put the 15-ton berg to the same use, creating some very real cracks in the term clean energy.

While they're still around, fatbergs have a strange pull on the city's tourists. The day we took our cameras down under, a couple on the street asked how they could arrange a tour as well. Paris actually offers a tour of its centuries-old sewers, as does Sydney, which raises the question of when an enterprising entrepreneur will market a tour of the world's dirtiest sewers (walk where Napoleon once relieved himself!).

London's bigger concern is how to stop fatbergs from forming in the first place. Earlier this year, Thames Water started a campaign using the phrase "bin it, don't block it" to remind people to capture their fat and grease and avoid washing it down the drain. Restaurants are the biggest producers of grease, and some have now set up fat traps under their sinks to catch congealed substances before they enter the sewers.

Yet having seen a berg up close makes us wonder if simply making people confront what their grease and fat are actually doing in the sewers might change their behavior. And not just seeing it, but smelling it too.

"You never forget your first time in the sewers," one of the junior sewer sweeps told me. He was right. After fully sensing exactly what happens under our feet to keep our streets clean, we were ready to head back to the street level.

"You'll never be so grateful for fresh air," the same guy told us. The smell of the bustling city street above us was indeed like perfume.

Thore Rehbach
Thore Rehbach

In Germany you need to engage a special service which exhausts the collected fat to run a restaurant...

Nilo Baranda
Nilo Baranda

Anthony Bourdain can clear that up with two giant baguettes.

Krustiono Basuki
Krustiono Basuki

many thing that not many people doesn't know what it is in our sewer system,.....

Ian M
Ian M

Do you not need facial masks when surrounded by a rushing river of feces ?

Rosanne Ting-Mak Brown
Rosanne Ting-Mak Brown

I always wondered what happened to all the fat that is drained down our sinks.   I think a tour would be a great idea, I went on the Paris Sewer Tour over 20 years ago when it first was great and I loved the opportunity to have seen something that not many people have seen before. :)

Rosanne Ting-Mak Brown
Rosanne Ting-Mak Brown

I always wondered what happened to all the fat that is drained down our sinks.   I think a tour would be a great idea, I went on the Paris Sewer Tour over 20 years ago when it first was great and I loved the opportunity to have seen something that not many people have seen before. :)

Carol Music
Carol Music

Interesting story about a usually disgusting topic. I can almost smell the 'fatbergs' after reading the author's description! And that isn't what I would call a 'good thing' . . .

 I can't imagine ever wanting to tour said sewers! That some do wish to and actually take tours speaks to the uniqueness of each of us! 

The idea that those 'fatbergs' can be used for good is great, though one does wonder how London's 'Chief Flusher' will manage to remove the mother of all fatbergs if it is, indeed, the size of a school bus!

It seems to be a better idea to continue educating locals to NOT dump the fat down the drains in the first place.


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