Thames Water, the private utility company responsible for the public water supply and waste water treatment in large parts of Greater London, plans to transform waste cooking fat to green energy, in order to tackle London's "fatberg" problem.

In charge of 43,500 miles of sewers underneath London, Thames Water's biggest headache is waste cooking fat poured down through kitchen sinks or toilets.

The cooled cooking fat then clings to wet wipes, plastics, or planks of wood and congeals into a "fatberg" blockage, a large immovable mass.

"The fatberg problem is vast," Craig Rance, spokesperson for Thames Water, told the Global Times.

"Every month Thames Water spends 1 million pound clearing blockages from London and surrounding area's sewers." Thames Water is planning to use the waste fat as a fuel.

"But we need to collect it before it goes in to the sewers and is contaminated with all the other nasty stuff in the pipes," Rance said. "If we can collect it from commercial kitchens and restaurants in fat, oil and grease traps that sit near sinks, we can refine this into a biofuel to produce biodiesel and green energy," he added.

In November, the company removed a fatberg the length of two buses under Whitehall, and in August, a team removed a Boeing 747-sized fatberg in West London.

The problem is even worse during the holidays, when people tend to cook at home more. The blockages can lead to homes being flooded with sewage. Not only is the smell disgusting, but fatberg is also very difficult to remove.

Engineers need to use high-pressure water jets to break up the blockage and then clear them out with special equipment.

Thames Water has encouraged people to bin the waste cooking fat instead of dumping it down the sinks, and suggested that people scrape leftovers and waste oil into bin before washing plates in the sinks. 

A 2012 survey found that there were 6.7 million blocked sinks in the UK each year, according to Rance.