Planes could soon run on pig fat – but it won't reduce emissions

Airlines could soon start using fuels made from animal fats to help them meet their climate targets. However, this could increase carbon emissions rather than reduce them, warns a report for campaign group Transport & Environment.

European Union regulations encourage the use of animal fats as a fuel and also require airlines to increase the proportion of “sustainable aviation fuels” they use by 2030. Several oil companies have announced plans to start producing aviation fuels from animal fats, which are expected to be the second main source of so-called sustainable fuels after used cooking oil.

There are two major issues with turning animal fats into jet fuel with the aim of reducing greenhouse gas emissions. The first is that, although animal fats are waste products of the meat industry, they are already used. “With used cooking oil, to a great extent, the biodiesel industry has given a use to something that wasn’t being well utilised, but it’s different with animal fats,” says analyst Chris Malins, the author of the report.

In 2006, the meat industries in the UK and European Union produced around 2.4 million tonnes of rendered, or purified, fat. In roughly equal proportions, this fat was used in pet food, to make products such as soap and to generate heat and power – often by the rendering factories themselves. Only a small percentage was turned into biodiesel.

In 2021, the UK and EU produced around 2.8 million tonnes of rendered fat, of which nearly half was turned into biodiesel, mostly for use in cars and trucks, with the rest going into pet foods and cosmetic products. Hardly any is used directly for heat and power any more.

This means that if the aviation industry starts using significant amounts of animal fat to make what it terms sustainable aviation fuel, there is going to be less for these existing purposes. The cosmetic and pet food industries are likely to replace it with palm oil, says Malins, as that is the cheapest product with similar properties.

That means more forests will be cleared to produce more palm oil, which could lead to emissions increasing by up to 70 per cent compared with carrying on using fossil fuels to power aircraft instead, the report says.

The second major issue is that using animal fat-based fuels gives the aviation industry a relatively cheap and easy way to help it meet the very modest targets for increasing the use of “sustainable aviation fuels”, says Malins. It is an alternative to investing in more expensive but better approaches such as cellulosic biofuels, which are made from the fibrous parts of plants, he says.

As there is little animal fat to go around this is no long-term solution. Demand for jet fuel in the EU is projected to reach about 46 million tonnes of crude oil equivalent a year by 2030. If all the animal fat produced in the EU were turned into jet fuel, it could supply at most 3 per cent of that, Malins calculates. That is unsurprising given it would take the fat from 8800 pigs to fuel a flight from Paris to New York.

There is a broader issue here. Using waste biomass can be truly green, unlike growing biomass for energy. But most waste biomass that can be used is being used, so regulatory incentives aimed at encouraging the use of waste can have unintended and undesirable consequences.

For instance, the EU’s incentives for turning used cooking oil into biofuel have led to countries in Asia exporting used cooking oil to the EU that was previously being fed to animals, among other things. Those countries then have to replace that oil with other products, raising emissions. In some cases, unused oil has even been sold as used, according to environmental campaigners. Similarly, much of the “waste wood” burned in power plants may not be waste at all.

As for aviation, the fact is that, for now, there simply are no genuinely sustainable zero-emission fuels available in anything like the quantities required. Aside from improving energy efficiency, in the short term, the only way to reduce aviation emissions is for people to fly less.