Can the UK limit Heathrow's climate impact?
British Chancellor Rachel Reeves has dismissed concerns about the climate impact of the expansion of London's Heathrow Airport, insisting there is "no trade-off" between continued economic growth and the UK's desire to decarbonise its economy.
Reeves said this week that the government would approve controversial plans to build a third runway at the UK's biggest airport, despite concerns that a surge in air traffic would jeopardise the country's progress towards carbon neutrality by the mid-2020s.
The math behind Reeves's claims rests on a big bet: that emissions-reducing technologies will be developed quickly enough to offset the increase in flights. But experts say these technologies are currently expensive and have not yet been tested on a large scale. The UK has set a legal target of achieving net zero emissions by 2050. More urgently, the country must reduce its emissions by 81% below 1990 levels over the next 10 years to meet new climate targets set by the UN. Air travel currently accounts for around 7% of UK emissions. In 2022, under the previous government, the UK published its 'Jet Zero' strategy, which promised 'zero-defect flights' powered by hydrogen, battery-powered aircraft and sustainable aviation fuels (SAF). Neither hydrogen nor battery-powered aircraft are ready for mass commercialisation. This means that for at least the next decade, the burden will fall on SAF.
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SAFs are broadly defined, including fuels produced from used cooking oils, synthetic fuels made from hydrogen and carbon dioxide, or biofuels made from plants and trees. It is difficult to calculate exactly how much they reduce carbon emissions over their life cycle compared to fossil kerosene and this depends on the type of SAF used. For example, the use of waste fuels in some cases results in almost no reduction in emissions. The UK government's strategy assumes that replacing kerosene with SAF results in a 70% reduction in life cycle emissions. The UK has asked airlines to replace 10% of their jet fuel with SAF by 2030 and 22% by 2040.
Chris Hilson, director of the Centre for Climate and Justice at the University of Reading, calls the UK's forecasts for SAF "overly optimistic" because the fuel is expensive and difficult to produce on a large scale. "Even with these fuels, flights will still produce significant emissions," he said.
A UK government spokesman said it was "committed to delivering a greener aviation sector." He added: "We have already made significant progress towards a greener aviation sector, with new targets for sustainable aviation fuel starting this year."
Heathrow declined to comment.
SAF currently costs at least twice as much as kerosene. The UK government's cost-benefit analysis suggests that its jet fuel target will cost around £11.4 billion by 2040. However, some of these costs will be mitigated by reducing the amount airlines have to pay in carbon credits.
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But this assumes there is enough jet fuel to meet the quota. Producers around the world are trying to get it going. BloombergNEF, a clean energy researcher, estimates that by 2030 there will be enough capacity to meet about 5% of global demand for jet fuel. Countries such as Brazil, Japan, South Korea and Indonesia are also planning to introduce jet fuel mandates, which will put further pressure on supply. The rise in aviation emissions will put pressure on other pillars of the UK's net zero emissions strategy. The government aims for 100% "clean" energy – mainly from renewable sources – by 2030. Analysis by Alex Chapman of the New Economics Foundation think tank predicts that expansions at Heathrow, Gatwick and Luton airports will cancel out the benefits of the Clean Power Plan within five years of its implementation. The runway is not expected to be built and operational until 2035. Even in the most optimistic scenarios, UK aviation is already projected to create a surplus of around 19 million tonnes of greenhouse gases by 2050, which the government plans to offset by using carbon removal technologies such as direct air capture – another technology that does not yet exist on a large scale. "You're growing something that doesn't have the capacity to decarbonize at the moment," said Alice Larkin, professor of climate science and energy policy at the University of Manchester.
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