In the next 30 years, the number of flights is expected to increase by 70 per cent. Unless things change, by 2050 the aviation industry will have used up more than a quarter of all the carbon dioxide we can safely emit while keeping global warming to under 1.5 degrees Celsius.
But the aviation industry says it has a way out. Sustainable Aviation, a UK coalition of airlines, airports and manufacturers announced earlier this month that the sector plans to reach net zero emissions by 2050. Its plan? Biofuels.
The group claims that switching to biofuels will reduce the amount of carbon dioxide planes put into the atmosphere by at least 30 per cent in 2050. But they might not be the carbon solution the aviation industry is in need of. Unless they’re used in the right way, biofuels could be a bigger source of carbon than expected, and won’t help reduce emissions at all.
Biofuel is an umbrella term for any fuel manufactured from organic material – an alternative to fossil fuels like oil, gas and coal which are formed by geological processes over long periods of time. They can be made from crops, wood or waste material which is turned into biodiesel and bioethanol. Although burning biofuels releases carbon into the atmosphere – the same as burning any fuel – the supposed benefit of biofuels comes from the fact that that carbon released was absorbed by the organic matter as it grew. In theory, this means that carbon simply cycles between plants and the atmosphere, rather than being released into the atmosphere after staying locked deep underground for millions of years.
At the moment Bergen, Brisbane, Los Angeles, Oslo and Stockholm airports provide a 50/50 mix of biofuel and jet fuel. Conventional fuels make the seal in the engines of older planes swell slightly which prevents leakage, so this mix is the minimum amount of fossil fuel that can be safely handled by all planes. Representatives from the International Air Transport Association (IATA) say that manufacturers are starting to use a synthetic rubber substitute in the engines of new planes that isn’t affected by biofuels, so over time they expect the percentage of biofuel used in the mix to go up.
But just because biofuels are made from plants, it doesn’t mean they’re carbon neutral. Although direct emissions from biofuel are lower than fossil fuels – burning enough biofuel to generate one megajoule of energy gives off the equivalent of 39g of CO2, whereas for fossil fuels that figure is 75.1g. But when you add in the carbon cost of growing and transporting biofuels, things become a lot more complicated.
“You can’t just say this is a biofuel, therefore it is five times better or tens times better,” says Chris Chuck, a professor of chemical engineering at the University of Bath. “But they know that that consumers want to hear that.” It all depends on how far you delve into the carbon cost of biofuel: how it is made and transported, and where the materials used come from. When this is taken into account, biodiesel from food crops emits an average of 1.8 times as much CO2 as fossil fuels which increases to three times more in case of biodiesel from palm oil. In 2017, a group of 177 dutch scientists signed an open letter to the government to stop biofuels made from food crops being included in the EU’s sustainable development agenda, calling it a “false solution”.
And growing crops for biofuels adds another problem to the mix: it requires vast tracts of land. World food demand is already set to increase by between 25 and 70 per cent by 2050 – and putting biofuel crops on top of this means there will be increased pressure on agriculture, cutting down on the environments that efficiently absorb carbon such as rainforests. “You’re driving deforestation and loss in high carbon stocks indirectly because of the biofuel demands,” says Laura Buffet, a director at Transport & Environment, a NGO that campaigns for sustainable transport in Europe.
Palm oil is one of the biggest offenders in carbon emissions when used to make biofuel. Carbon-capturing forests are burned down to make way for palm oil plants, which are less efficient at taking carbon out of the air. The carbon emissions from the land-use change of palm oil are 4.2 times higher than the amount of carbon it emits directly as fuel. Even if there is a reduction in emissions when the biofuel is used, its overall cost to the planet is 303 per cent worse than fossil fuels.
Sustainable Aviation says that to avoid this issue, only waste products from farming will be used. But her things aren’t clear either. There are problems when it comes to what is defined as waste – if you use waste palm oil products it stays within this allowance still contributes to the environmental farming issues.
Even substances that seem like waste – such as straw – might be better off being returned to the soil to help maintain nutrient levels. Soil holds three times more carbon than the atmosphere, but in the UK arable soils have lost 40 to 60 per cent of their organic carbon due to intensive agriculture. Adding pressure on farming means the available land will need to be farmed more intensively in order to meet demands.
“There’s a big risk that we will take a problem from sectors like airlines who are resisting attempts to curb their growth and transfer it to farming,” says Jo Lewis, policy director at the Soil Association. The charity is trying to prevent intense farming practices to reduce their impact on the climate crisis, but this will be harder if the waste products needed to create a system of putting nutrients back into the soil are taken away.
Since biofuel was first approved for use in 2011, 230,000 commercial flights have been run on a biofuel/fossil fuel mix, but this is only a tiny dent in the more than 102,400 flights that take off every day. And no matter what fuel they are burning, there’s the added problem that releasing carbon and other pollutants high in the atmosphere may have a worse effect on the environment than releasing them close to the ground. For now at least, biofuels aren’t quite the silver bullet the aviation industry is hoping they’ll turn out to be.
Maria Mellor is a writer for WIRED. She tweets from @Maria_mellor
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