Europe’s growing use of SAFs derived from animal fats is becoming "increasingly unsustainable", according to Transport and Environment (T&E).

A T&E study revealed use of animal fat biodiesel has doubled over the past 10 years and is 40 times higher than it was in 2006, with demand set to triple by 2030.

T&E, though, has warned there won’t be enough by-products from industrial meat farming to sustain this level of demand, with nearly half of all waste European animal fats already going into biodiesel.

According to T&E, the fuel required to power a single flight from Paris to New York would need the fats derived from nearly 9,000 pigs.

Citing projections produced by Stratas Advisors, T&E said animal fats are likely to be the most common waste feedstock for SAFs, alongside cooking oil. The organisation is calling for greater transparency around what goes into the feedstocks used to produce SAF.

In addition, T&E said the use of potential replacements could be equally problematic. T&E’s biofuels expert, Barbara Smailagic, said current usage could only be sustained by depriving other sectors, which would likely lead to the use of "damaging alternatives like palm oil".

“The competing uses for animal fats lay bare the challenge of scaling up waste biofuels production," said Smailagic, who added demand could fuel "industrial scale" fraud as opportunist criminals seek to mislabel alternatives to animal fats.