Can we turn the Whitechapel fatberg into biodiesel?

For a 130-tonne mass of grease, bound as hard as concrete by thousands of tampons, wipes and used tissues, the Whitechapel fatberg is in surprisingly high demand.

Last week, the Museum of London announced it wants to display a chunk of the human-waste bomb, recently unearthed in east London, as a way “to raise questions about how we live today”. Now, a Scottish biodiesel company is taking a piece to turn into fuel.

Argent Energy has spent more than 10 years turning waste that would otherwise go to landfill into biodiesel, a process it has ramped up since the opening this year of a new plant at Ellesmere Port in Cheshire.

“We’re always looking for new sources,” says Dickon Posnett, one of the company’s bosses. “We’ve done rancid mayonnaise, old soup stock that has been sitting in tanks for years, and now we’re playing with fatbergs.”

Sewage sludge, taken from the water-treatment process at various stages in cities across the country, now makes up about 10% of Argent’s intake (food and agricultural waste make up most of the rest). The sludge is heated to melt the fat, which is separated from the debris and processed and squeezed to create a clean oil. The oil is further processed with chemicals to make biodiesel, which Argent supplies to fleets of buses and trucks in the UK, Europe and the US.

Posnett calculates that the new plant could process 300,000 tonnes of fatberg a year – enough to fill more than 50,000 lorries with biodiesel, which creates a fraction of the polluting emissions of standard fuel. The government has just raised its target for the percentage of renewable fuel in petrol and diesel to just under 10% by 2020, up from the current 4.75%, raising demand for new sustainable sources of fuel.

As unfortunate sewer miners continue to hack away at the Whitechapel fatberg (about half of it has been excavated so far), Argent is already supplying biodiesel, blended at 20% with standard diesel, to Metroline, one of London’s biggest bus operators. Thames Water is anxious for its 15 million customers to stop putting fat and wet wipes, among other clogging agents, down our drains. In the meantime, a growing number of bus passengers in London are being propelled by their own effluent, mined from the rich seams of fat beneath our streets.