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A fatberg is a rock-like mass of waste matter in a sewer system formed by the combination of flushed non- biodegradable solids, such as
wet wipe A wet wipe, also known as a wet towel or a moist towelette, disposable wipe, disinfecting wipe, or a baby wipe (in specific circumstances) is a small to medium-sized moistened piece of plastic or cloth that either comes folded and individually ...
s, and fat, oil and grease (FOG) deposits. The handling of FOG waste and the buildup of its deposits are a long-standing problem in waste management, with "fatberg" a more recent neologism. Fatbergs have formed in sewers worldwide, with the rise in usage of disposable (so-called "flushable") cloths. Several prominent examples were discovered in the 2010s in Great Britain, their formation accelerated by aging Victorian sewers. Fatbergs are costly to remove, and have given rise to public awareness campaigns about flushable waste.


Formation

Fatbergs form at the rough surfaces of sewers where the fluid flow becomes
turbulent In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...
. In pipes and tubes with smooth inner linings, fluid near the containing wall flows only slightly slower than fluid in the central channel of the pipe; thus, the whole volume of fluid flows smoothly and freely. When fluid encounters an obstruction, a resulting swirl of water starts trapping debris. Fatbergs occur in sewer systems around the globe, in cities and smaller towns. An obstruction can be any type of rough surface capable of snagging debris. In brick or concrete sewers there may be surplus cement drips, damaged brickwork, or loose mortar joints damaged by
frost heave Frost heaving (or a frost heave) is an upwards swelling of soil during freezing conditions caused by an increasing presence of ice as it grows towards the surface, upwards from the depth in the soil where freezing temperatures have penetrated in ...
. In any sub-surface pipe, even of the most advanced design, penetration by foreign intrusions such as tree roots is a commonplace cause of a fatberg blockage. Fatbergs are not just the result of fats that have congealed through cooling. The
lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids includ ...
s in fatbergs have undergone a process of
saponification Saponification is a process of converting esters into soaps and alcohols by the action of aqueous alkali (for example, aqueous sodium hydroxide solutions). Soaps are salts of fatty acids, which in turn are carboxylic acids with long carbon chains. ...
. Fatbergs thus require four main components:
calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...
, free fatty acids, FOG, and water. Comprising not only wet wipes and fat, fatbergs may contain other items that do not break apart or dissolve when flushed down the toilet, such as sanitary napkins,
cotton bud Cotton is a soft, fluffy Staple (textiles), staple fiber that grows in a wikt:boll, boll, or protective case, around the seeds of the cotton plants of the genus ''Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose ...
s, needles, condoms and
food waste Food loss and waste is food that is not eaten. The causes of food waste or loss are numerous and occur throughout the food system, during production, processing, distribution, retail and food service sales, and consumption. Overall, about o ...
washed down kitchen sinks. The resulting lumps of congealed material can be as strong as concrete, and require specialist equipment to remove. In the United States, almost half of all sewer blockages are caused by grease, combined with the evergrowing use of wipes that end up in sewer systems.


Impact

Fatbergs can cause blockages in sewer systems. Giant fatbergs have blocked sewers in London, New York, Denver, Valencia, and Melbourne. Blocked fat reacts with the lining of the pipe and undergoes
saponification Saponification is a process of converting esters into soaps and alcohols by the action of aqueous alkali (for example, aqueous sodium hydroxide solutions). Soaps are salts of fatty acids, which in turn are carboxylic acids with long carbon chains. ...
, converting the oil into a solid, soap-like substance. Grease and fat blockages can cause
sanitary sewer overflow Sanitary sewer overflow (SSO) is a condition in which untreated sewage is discharged from a sanitary sewer into the environment prior to reaching sewage treatment facilities. When caused by rainfall it is also known as wet weather overflow. Cause ...
s, in which sewage is discharged into the environment without treatment. Fatbergs have been considered as a source of fuel, specifically
biogas Biogas is a mixture of gases, primarily consisting of methane, carbon dioxide and hydrogen sulphide, produced from raw materials such as agricultural waste, manure, municipal waste, plant material, sewage, green waste and food waste. It is a ...
. Most of the fatberg discovered in Whitechapel in London in 2017, weighing and stretching more than , was converted into
biodiesel Biodiesel is a form of diesel fuel derived from plants or animals and consisting of long-chain fatty acid esters. It is typically made by chemically reacting lipids such as animal fat ( tallow), soybean oil, or some other vegetable oil ...
.


Mitigation

Fatbergs can be mitigated through public awareness campaigns about flushable waste and grease traps for filtration at the source. Campaigns have been launched against wet wipes because of their effect on sewer systems, most notably by
Surfers Against Sewage Surfers Against Sewage (SAS) is a marine conservation charity working with communities to protect oceans, waves, beaches and marine life. It was created in 1990 by a group of Cornish surfers from the villages of St Agnes and Porthtowan on the nor ...
and the
Marine Conservation Society The Marine Conservation Society is a UK based not-for-profit organization working with businesses, governments and communities to clean and protect the oceans. Founded in 1983, the group claims to be working towards "cleaner, better-protected, h ...
, among other environmental NGOs, who called on the UK's Advertising Standards Authority to end “misleading” branding and packaging. In 2022, Australia and New Zealand developed a product labelling standard to help determine if a product is flushable.


Etymology

Fatberg is a
compound Compound may refer to: Architecture and built environments * Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall ** Compound (fortification), a version of the above fortified with defensive struc ...
of the words ''fat'' and '' iceberg''. The word was used in 2008 to describe "large, rock-like lumps of cooking fat" washing up on beaches in Wales, and by 2010 was used in reference to sewer-blocking fat deposits in London. The word was added to
Oxford Dictionaries Online Lexico was a dictionary website that provided a collection of English and Spanish dictionaries produced by Oxford University Press (OUP), the publishing house of the University of Oxford. While the dictionary content on Lexico came from OUP, th ...
in 2015. The term is used by authorities at
Thames Water Thames Water Utilities Ltd, known as Thames Water, is a large private utility company responsible for the public water supply and waste water treatment in most of Greater London, Luton, the Thames Valley, Surrey, Gloucestershire, north Wiltsh ...
and
South West Water South West Water provides drinking water and waste water services throughout Devon and Cornwall and in small areas of Dorset and Somerset. South West Water was created in 1989 with the privatisation of the water industry. It was preceded by the ...
, both in southern England.


Notable fatbergs

*6 August 2013: A fatberg roughly the size of a bus that weighed , consisting of food fat and wet wipes, was discovered in drains under London Road in
Kingston upon Thames Kingston upon Thames (hyphenated until 1965, colloquially known as Kingston) is a town in the Royal Borough of Kingston upon Thames, southwest London, England. It is situated on the River Thames and southwest of Charing Cross. It is notable ...
, London. * 1 September 2014: A solid mass of waste fat, wet wipes, food, tennis balls and wood planks, the size of a Boeing 747 aeroplane was discovered and cleared by sanitation workers in a drain beneath a section of road in Shepherd's Bush, London. * 3 September 2014: The sewerage system beneath
Melbourne Melbourne ( ; Boonwurrung/Woiwurrung: ''Narrm'' or ''Naarm'') is the capital and most populous city of the Australian state of Victoria, and the second-most populous city in both Australia and Oceania. Its name generally refers to a met ...
, Australia was clogged by a large mass of fat, grease and waste. * January 2015: As part of a campaign against drain blocking,
Welsh Water Welsh may refer to: Related to Wales * Welsh, referring or related to Wales * Welsh language, a Brittonic Celtic language spoken in Wales * Welsh people People * Welsh (surname) * Sometimes used as a synonym for the ancient Britons (Celtic peopl ...
released a video showing a fatberg in drains in
Cardiff Cardiff (; cy, Caerdydd ) is the capital and largest city of Wales. It forms a principal area, officially known as the City and County of Cardiff ( cy, Dinas a Sir Caerdydd, links=no), and the city is the eleventh-largest in the United Kingd ...
. * April 2015: A fatberg was removed from sewers under
Chelsea Chelsea or Chelsey may refer to: Places Australia * Chelsea, Victoria Canada * Chelsea, Nova Scotia * Chelsea, Quebec United Kingdom * Chelsea, London, an area of London, bounded to the south by the River Thames ** Chelsea (UK Parliament consti ...
. It took over two months to remove, and the damage it caused cost an estimated £400,000 to repair. * July 2015: A fatberg was discovered in
Welshpool Welshpool ( cy, Y Trallwng) is a market town and community in Powys, Wales, historically in the county of Montgomeryshire. The town is from the Wales–England border and low-lying on the River Severn; its Welsh language name ''Y Trallwng'' m ...
in mid-Wales. * January 2016: A blockage caused by a fatberg near
Newcastle, New South Wales Newcastle ( ; Awabakal: ) is a metropolitan area and the second most populated city in the state of New South Wales, Australia. It includes the Newcastle and Lake Macquarie local government areas, and is the hub of the Greater Newcastle area ...
, Australia, damaged the
Eleebana Eleebana is a suburb of the City of Lake Macquarie in New South Wales, Australia, from Newcastle's central business district along the eastern shoreline of Lake Macquarie. History Eleebana remained unsettled until it became part of the Newca ...
sewage pumping station. The fatberg "weighed about and took four hours to remove" by crane. * September 2017: A fatberg weighing over was found under Whitechapel, London. Even working seven days a week at a cost of £1 million per month, officials estimated it would take two months to destroy it. Two pieces of the fatberg were cut off on 4 October 2017 and, after several weeks of drying, were displayed at the
Museum of London The Museum of London is a museum in London, covering the history of the UK's capital city from prehistoric to modern times. It was formed in 1976 by amalgamating collections previously held by the City Corporation at the Guildhall Museum (fou ...
from 9 February 2018 through June 2018, as part of the museum's City Now City Future season. According to curator Vyki Sparkes, the fatberg became one of the museum's most popular exhibits. * September 2017: A fatberg of congealed fat, wet wipes, and waste was discovered under the streets of
Baltimore, Maryland Baltimore ( , locally: or ) is the List of municipalities in Maryland, most populous city in the U.S. state of Maryland, fourth most populous city in the Mid-Atlantic (United States), Mid-Atlantic, and List of United States cities by popula ...
that caused the spillage of of sewage into
Jones Falls The Jones Falls is a U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map , accessed April 1, 2011 stream in Maryland. It is impounded to create Lake Roland before running through the city of Baltim ...
. * April 2018: A fatberg discovered under South Bank in London is suspected to be larger than the one found under Whitechapel. * 12 September 2018: Workers in
Macomb County, Michigan Macomb County ( ) is a county located in the eastern portion of the U.S. state of Michigan, bordering Lake St. Clair, and is part of northern Metro Detroit. As of the 2020 Census, the population was 881,217, making it the third-most populous c ...
discovered a fatberg 100 feet long, 11 feet wide and as much as 6 feet tall. The Michigan Science Center launched a 'fatberg' exhibit in December 2018, which included real pieces from the mass found in September. * December 2018: Sewer workers discovered a fatberg in
Sidmouth Sidmouth () is a town on the English Channel in Devon, South West England, southeast of Exeter. With a population of 12,569 in 2011, it is a tourist resort and a gateway to the Jurassic Coast World Heritage Site. A large part of the town h ...
, Devon that was long. Workers took eight weeks to remove it. It was the largest fatberg discovered in the UK outside a major city, and the largest in the history of
South West Water South West Water provides drinking water and waste water services throughout Devon and Cornwall and in small areas of Dorset and Somerset. South West Water was created in 1989 with the privatisation of the water industry. It was preceded by the ...
. * February 2019: The largest fatberg in the UK was discovered in a sewer at Birchall Street in Liverpool. It weighed and was long. It proved to be difficult to break down using conventional tools and equipment. It was finally removed in May 2021 using a new method of clearing, which consisted of workers feeding a steel rope through it and then cutting it with a jet. *December 2019: A large fatberg in the north of England was reported by United Utilities under
HM Prison Manchester HM Prison Manchester is a Category A and B men's prison in Manchester, England, operated by His Majesty's Prison Service. It is still commonly referred to as Strangeways, which was its former official name derived from the area in which it is ...
. The fatberg was estimated to weigh "around the same as three elephants", taking several weeks to remove fully. *April 2020: A fatberg the size of a petrol tanker was discovered in
Melbourne Melbourne ( ; Boonwurrung/Woiwurrung: ''Narrm'' or ''Naarm'') is the capital and most populous city of the Australian state of Victoria, and the second-most populous city in both Australia and Oceania. Its name generally refers to a met ...
, Australia. Its unusually large size in relation to other Australian blockages (far exceeding the 2014 and 2016 Australian fatbergs) was blamed primarily on the shortage of toilet paper caused by the COVID-19 outbreak. *26 June 2020: Two years after a large mass of fat was jet cleaned from Gisborne's sewer network in
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
, a half-tonne fatberg built up in the same place. The second fatberg an overflow of the wastewater system, which the
Gisborne District Council Gisborne District Council ( mi, Te Kaunihera o Te Tairāwhiti) is the unitary authority for the Gisborne District of New Zealand. The council consists of a mayor and 13 ward councillors. The district consists of the city of Gisborne and a largel ...
attributed this to COVID-19 claiming that they "had significant problems with pump stations blocking because more people were at home and their behaviour had changed." *October 2020: A 10-tonne fatberg made up of grease, fat, and wet wipes was removed from sewers under Cadogan Place in
London London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...
, England. *February 2021: A "huge and disgusting" fatberg described as having the same weight as a bungalow was removed from under Yabsley Street in
Canary Wharf Canary Wharf is an area of London, England, located near the Isle of Dogs in the London Borough of Tower Hamlets. Canary Wharf is defined by the Greater London Authority as being part of London's central business district, alongside Central Lon ...
, London, England. *April 2021: A giant fatberg, weighing about 300 tonnes, was found to be clogging a sewer in the
Hodge Hill Hodge Hill is an area 4 miles east of Birmingham City Centre, England. It is also a council constituency, managed by its own district committee. The MP of Hodge Hill is currently Liam Byrne. The constituency includes the smaller constituenc ...
area of
Birmingham Birmingham ( ) is a City status in the United Kingdom, city and metropolitan borough in the metropolitan county of West Midlands (county), West Midlands in England. It is the second-largest city in the United Kingdom with a population of 1. ...
, England.
Severn Trent Severn Trent plc is a water company based in Coventry, England. It supplies 4.6 million households and business across the Midlands and Wales. It is traded on the London Stock Exchange and a constituent of the FTSE 100 Index. Severn Trent, the ...
commented that it was estimated to be one of the biggest blockages they had ever dealt with.


References

{{reflist Sewerage Sewerage infrastructure