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In London’s Sewers: Less Pollution and A Smelly Form of Energy

Before you go into a sewer, you have to follow a very detailed checklist. You need to gear up in several layers of protective clothing, including hip waders and a disposable jumpsuit. You need multiple pairs of latex gloves, in case the top layer gets dirty, which it inevitably will in a tunnel where every surface is literally covered in human excrement. Then, after donning a hard hat, you need to be lowered down about 20 feet into a manhole. The moment you touch down, the smell is instantly overwhelming.

There are a few reasons to visit London’s sewers, or at the very least, think about them. The British capital has one of the oldest networks in the world—1,200 miles of underground tunnels built in the 1860s by a British engineer named Joseph Bazalgette. Through the industrial revolution and both world wars, those tunnels carried water and waste away from the constantly growing population of London. Now, after more than a century and a half of being taxed, the system needs some work. In the process, it’s also yielding a highly valuable and undeniably repulsive source of energy.

We were given a tour of one part of the sewer system by Thames Water, the public utility that manages all of London’s water infrastructure. We wanted to see how a sewer worked and to understand what was needed to retrofit the system underneath one of the world’s biggest cities. We were told to meet at a nondescript manhole cover in central London. And to bring plastic trash bags to cover our cameras. Mishaps, apparently, are quite common.

Despite what you’d think, it’s not only human waste that runs in the rivers of sewers. There’s lots of oil, especially after it rains and washes off the streets. There are leaves and dirt and garbage. We were also warned not to be surprised at the number of condoms that line the wall, stuck there by a fungus that thrives in the dark humidity.

What builds up the most is fat—cooking oil and grease that people wrongly wash down the drains instead of throwing in the garbage. Over time, that grease, which can’t be dissolved by water, amasses into a large pile. It’d be hard to think of a more perfect name than what sewer managers call them: fatbergs. A small mountain of built up fat smells about the way you’d imagine. When I reached out and grabbed some to feel its texture, several sewer workers looked on and simply shook their heads at my foolishness. Once you break the outer seal of a fatberg, I was later told, the stench multiplies.

Because of what they’re made of, fatbergs can actually be burned for energy. They’re highly caloric, which makes them able to be burned very efficiently for a long time. City engineers ordered up a new power plant in East London to incinerate the bergs. If all goes as planned, they’ll produce 130 gigawatts of power each year, enough to power about 40,000 homes.

The other reason we wanted to see London’s underground rivers was because of the way it’s changing for the future. Most of London’s focus and money at the moment has gone toward expanding the sewer system to accommodate a heavier flow of water, especially when it rains and dirty storm water overflows the system. With nowhere to put it, the polluted water is dumped into the River Thames.

London’s answer is a new bit of ambitious infrastructure called the Tideway Tunnel. It will funnel the overflow sewage to a treatment plant. “This tunnel might be the last change we’ll ever have to make to the sewer system, perhaps ever,” Rob Smith, technical coordinator for Thames Water told us. The utility’s engineers have said that when the project is done in 2016, it’ll be built to last for 100 years.

To the people who work in London’s sewers, the network of pipes can be a metaphor. The growing rivers of waste literally illustrate London’s growing consumption. The fatbergs symbolize a city’s clogging arteries. The expansion of the system signifies a city on the move, planning for a cleaner and more efficient future. Thinking about a sewer’s higher meaning, we learned, is a way to pass the time underground. But the smell is something you never get used to.