They might be some of the foulest-smelling things imaginable.
But scientists say that stinking fatbergs could form the basis of some beautiful perfumes.
Fatbergs are vast blobs of wet wipes, used condoms, plastic bags, and sanitary products all held together by a congealed mass of fat and grease.
Now, researchers at the University of Edinburgh have found a way to transform these nightmares from the sewers into a fragrant oil with the scent of pine needles.
Chunks of the fatberg are fed to specially engineered bacteria that have been genetically programmed to eat sewer waste.
Over time, these bacteria break down the fatberg into a valuable chemical used in the perfume industry.
In the future, bacteria like this could even be released into sewage plants to break down fatbergs and leave the sewers smelling better than ever.
Professor Stephen Wallace, lead researcher on the project, told MailOnline: ‘Imagine these new bacteria living in the sewers breaking down fatbergs and turning them into sweet-smelling chemicals.’
Fatbergs form as solid waste flushed down the toilet combines with oils like cooking fat or conditioner to create a solid mass of dense material.
At their largest, they can grow to be several tonnes in weight and cause serious problems for the sewer system as blockages lead to backed-up drains and even flooding.
One of the largest ever recorded was the so-called Whitechapel Fatberg, which weighed 130 tonnes and was as long as London Bridge.
Thames Water says it spends £18 million every year clearing these monstrosities from the sewers, with the Whitechapel Fatberg alone costing £220,000 to remove.
But in Professor Wallace’s bioengineering lab, researchers are working hard to find a way of turning this trash into treasure.
He says: ‘Fatbergs are currently a huge problem facing our sewer systems in the UK, and when these are removed, they are currently incinerated or sent to landfill.
‘They are also made of fats, and we know that bacteria love fats, and so we thought maybe we can reprogram bacteria to eat the fats and transform them into something useful?’
Professor Wallace buys chunks of fatberg from a company which specialises in removing them from the pipes beneath cities.
These chunks are then steamed to kill any harmful pathogens before being fed to a colony of genetically engineered bacteria.
Professor Wallace says: ‘We use a new field of science called “engineering biology” where we can take DNA from throughout nature, in this instance from plants, and insert it into bacteria to program biological systems to do new things.’
In this case, that genetic code allows them to feed on the sewer waste and produce a chemical called pinene which is normally found in pine needles.
That chemical is extremely valuable throughout the cosmetic industry and is used in everything from perfumes to shower gels.
Professor Wallace says that his team can’t yet produce enough of the fragrance to make this commercially viable.
However, he adds that the lab is ‘currently working with UK industry partners’ to see whether this could be a possibility.
Normally, when fatbergs are removed from the sewers, they are either thrown into landfill or burned – leaking chemicals into the ground or producing greenhouse gases.
But bioengineering innovations like this open up more ways of turning this waste into something useful.
Similar techniques have been used to convert fatbergs into biofuels like methane by letting bacteria feed on the fats and oils inside.
However, Professor Wallace says that his innovations could one day stop fatbergs from forming in the first place.
Although he says that the bacteria couldn’t be released into the sewer due to the ‘important ethical concerns’ of releasing new species, they could be put to work in sewage treatment.
Bacteria in the water could eat the fats and oils which bind fatbergs together before they reach the point that specialist clearing crews are needed.
And, as an added bonus, bacteria engineered to produce pinene would leave sewer water smelling fantastic.
Professor Wallace concludes: ‘One could imagine sewage treatment facilities using this new technology to reduce the smells associated with them.
‘This genuinely has the potential to be a transformative solution to the climate crisis and to creating a more sustainable future for future generations.’
WHAT ARE FATBERGS?
Fatbergs are blockages made up of flushed fat, oil, grease and other flushed waste such as wet wipes and illegal drugs.
They form into huge concrete-like slabs and can be found beneath almost every UK city, growing larger with every flush.
They also include food wrappers and human waste, blocking tunnels – and raising the risk of sewage flooding into homes.
They can grow metres tall and hundreds of metres long, with water providers last year declaring an epidemic of fatberg emergencies in 23 UK cities, costing tens of millions of pounds to remove.
The biggest ever discovered in the UK was a 750-metre (2,460ft) monster found under London’s South Bank in 2017.
Fatbergs take weeks to remove and form when people put things they shouldn’t down sinks and toilets.
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