Turning Fatbergs Into Biofuel

Researchers have developed a new method for recycling greasy sewer blockages into green fuel

FOG (fats, oils and greases) in various stages of treatment (UBC)
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A few years ago, many of us became acquainted with a singularly revolting word: fatberg. The word described an increasingly common scenario in the world’s sewer systems, wherein cooking oils and other greases congeal in the pipes, creating sludgy masses that entrap any number of disposed solids. Materials commonly found in fatbergs include wet wipes, sanitary pads, condoms and food scraps. The fatbergs look, in underground photos, like an explosion at the Crisco factory: globby whitish material clinging to the sides of sewer tunnels, waxy chunks breaking off and moving slowly forward on sluggish rivers of grease.

Disgusted yet? You should be. Not only are fatbergs gross to think about, they wreak havoc on sewer systems, causing clogs and overflows. They’ve vexed public works officials and cost taxpayers millions in cities from London to Baltimore to Melbourne in recent years.

But a team of Canadian researchers say these fatbergs could actually be put to good purpose, as biofuel. While they're not the first scientists to attempt this—any fat can be turned into biofuel—they say their method is more efficient, and can actually work inside the sewer system, no need to scoop the fatbergs out and take them off for processing.

“This method would help to recover and reuse waste cooking oil as a source of energy,” says Asha Srinivasan, an engineering researcher at the University of British Columbia (UBC) who worked on the study, recently published in the journal Water, Air, & Soil Pollution.

The method works like this: FOG [fats, oils and greases, the building blocks of fatbergs] are heated to between 90 and 110 degrees Celsius, then hydrogen peroxide is added to break down organic matter and release fatty acids. Bacteria are then used to break down the fatty acids, producing methane.

“Finding the right combination of microwave temperature and hydrogen peroxide dosage is the key to the success of the process,” Srinivasan says. “Our process helps to break down FOG, making it easy for the bacteria to digest and produce more methane.”

These methods could eventually be used by municipal water treatment programs to destroy fatbergs—adding pretreated FOG to the system could start the breakdown process. It could also be useful for farmers, allowing them to put more FOG into their biogas digesters, the tanks used to treat farm waste. Currently farmers can only use a limited amount of FOG in the digesters—about 30 percent FOG to 70 percent cow manure or other wastes. The new technique, which breaks FOG into simpler materials, enables them to use up to 75 percent FOG. This means they can both recycle more oil waste and produce more methane.

“It’s a clever idea,” says Chad Jafvert, a professor of civil engineering at Purdue University, but adds that cost will be a factor in the process’s wider adoption, as it takes energy to heat the materials. In-field testing will yield more information about price and efficiency.

Right now the UBC team is working on pilot tests at municipal sewage treatment plants and dairy farms. The next step will be to identify the optimum ratio of FOG to sludge or farm manure. They expect to have a full-scale system in place locally within the next two years. After that, the process could be easily adopted by other sewage treatment systems, Srinivasan says.

While turning fatbergs into fuel is a potential way to make some good out of a bad situation, the best solution would be to prevent these fatbergs from forming in the first place. How? Quit pouring grease down the drain and flushing wet wipes, even those marked ‘flushable,’ say experts. Instead of tipping used cooking oil down the sink, allow it to congeal in a disposable container and toss it in the trash. Scrape your plate of grease and food scraps before washing or loading the dishwasher. Restaurants also need to be careful about the proper disposal of cooking grease.

If you’re not thoroughly grossed out yet, perhaps you’d enjoy a little fatberg watching? The Museum of London has just set up a live-streaming “FatCam,” with 24/7 viewing of its slice of the infamous 143-ton Whitechapel Fatberg, which clogged sewers in the city’s East End in 2017. The fatberg chunk was on public display (and extremely popular) until last month, when it began growing a toxic yellow mold.

Happy viewing! And keep those wet wipes out of the toilet.

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