Tapping Energy From Fatbergs | Fluence

Grease in sewer pipes caused big maintenance problems recently for the 502nd Civil Engineer Squadron and the San Antonio Water System.

Fatbergs, massive accretions of grease and debris, are a big problem in sewers, but decentralized and sustainable solutions have been proposed

It weighed as much as a blue whale and was even longer, but Londoners didn’t realize it was lurking beneath their streets until ancient sewer tunnels backed up. The blockage turned out to be the world’s largest recorded fatberg, a monolithic mass of congealed fat, hygiene products, and other debris.

Travis Andrews of The Washington Post wrote that the colossal fatberg weighed 130 tons and was more than 250 yards long. Fatbergs, given their size and composition, present a massive cleanup problem. Municipalities have legislated and created awareness programs to change fat-disposal behavior in their populations, and researchers have proposed decentralized wastewater treatment solutions to stop fatbergs before they form. The blockages also present opportunities: One company in the United Kingdom even plans to remove oil-rich fatbergs from sewer tunnels and generate electricity from them.

Fatberg Formation

Sewer systems worldwide have experienced blockages from congealed fat and debris, but sewers in the U.K. seem particularly vulnerable to excessive fatberg formation for several reasons. Avery Thompson of Popular Mechanics explains that it’s partly due to lax regulations on grease traps:

Most cities in the U.S. require restaurants to […] maintain their own grease traps, but the rules in the U.K. make implementing similar regulations difficult.

Thompson also said exposure to calcium from concrete sewer tunnel walls hardens the abundant fat into a solid, soaplike substance.

But there’s more to a fatberg than fat and calcium. As mentioned, disposable hygiene products, including the seemingly innocent “flushable” wet wipes so common in modern countries, add to and strengthen fatbergs as they grow.

Fighting Fatbergs

To combat fatbergs, Vancouver, in the Canadian province of British Columbia, has been taking the approach of voluntary compliance with its “Wipe It, Green Bin It” public awareness campaign to modify how the public disposes of cooking oil and fat. CTVNews reports that the campaign encourages people to scrape or wipe grease and oil from butter dishes and cooking pans, then compost the grease instead of disposing of it in drains.

Washington, D.C., is seeking to control one of the main catalysts of fatberg formation in its sewer system by legislating the conditions under which a company may label its wet wipes as “flushable.” Katherine Shaver of the Chicago Tribune recently reported on the Washington law passed in response to wipes that are sold as flushable but allegedly jam and clog equipment at wastewater treatment plants. The problem costs U.S. utilities up to $1 billion annually, according to the National Association of Clean Water Agencies.

A pending lawsuit filed by Kimberly-Clark, a Texas-based wet wipes manufacturer, has contested the law on constitutional grounds.

Decentralized Treatment’s Role

Researcher Thomas Phillip Fudge has suggested a new approach to the fatberg problem. He stresses that smaller, decentralized water treatment solutions can be deployed to remove fats and other compounds more efficiently than large facilities.

Once comparatively concentrated wastewater enters a municipal sewer system, it mixes with a much larger volume of rainwater, exponentially increasing the amount of water that must be treated. A decentralized solution avoids this needless flood of water by treating the wastewater near its source, where it is still relatively concentrated, greatly reducing the scale of the job.

Fudge states in phys.org’s the Conversation:

The solution is to build small treatment plants in new developments or renovations that service smaller areas.

He envisions not only removing the fats that form fatbergs, but also extracting biogas from sewage for heating and cooking, a process that would be much more difficult with highly diluted wastewater.

Tapping Fatbergs’ Power Potential

The company 20C sees existing fatbergs as an opportunity. It recently concluded a 200-million-pound (US$264 million) deal with Thames Water to generate enough electricity to power 39,000 homes using the fatbergs as fuel, reported Christopher York of Huffington Post U.K. As part of the deal, 75 GWh of the electricity generated from fatbergs will power nearby desalination and wastewater treatment facilities.

Although not all fatbergs grow to a grand scale, they do create different levels of havoc for sewer systems across the world. But, until they’re stopped before they form, cities are adopting diverse strategies to exploit the energy trapped beneath their streets.

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