Royal Society report on novel aviation fuels – no option other than cutting demand for flying
The UK government has been promoting the idea of “guilt-free flying” in a few years time. Now a report from the Royal Society says (as has been well known by anyone who properly investigated the issue!) that there is currently no single, clear alternative to traditional fuel. Switching to so-called “sustainable” fuel is key to the government’s aim to reach “jet zero” flying by 2050. Realistically, there will be no significant impact on reducing aviation CO2 from electric planes, or hydrogen. Small economies and efficiencies by airlines can only make a small dent, while demand for flights is expected to increase. The Royal Society looked at options for “greener” fuels to replace the 12.3m tonnes of jet fuel used annually in the UK. They conclude that to produce biofuels for UK aviation would require half of Britain’s farming land, putting severe pressure on food supplies and nature. There is not enough genuinely low carbon electricity to produce much “green” hydrogen. The Royal Society says research and development is required to understand and mitigate the non-CO2 climate impacts of all the alternative fuel options. But it stops short of the obvious solution to reducing aviation carbon emissions – reducing the demand for air travel, and not allowing it to grow.
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Royal Society report (80 pages) is at
Net zero aviation fuels: resource requirements and environmental impacts
https://royalsociety.org/topics-policy/projects/low-carbon-energy-programme/net-zero-aviation-fuels/
Aviation is a contributor to global warming, including through the emissions of carbon dioxide and the formation of contrails high up in the atmosphere. Globally, save for the few years of the pandemic, air travel is expected to continue to grow in the future, increasing the impact on climate change unless a close to net zero form of flying can be developed or any residual emissions offset by removals.
If low carbon emission jet fuels are to have a strong positive impact on the UK’s Road to Net zero, it is important that the alternative fuels adopted are truly beneficial to the fight against the climate crisis and do not cause unacceptable collateral ecological damage.
What are the options for net zero aviation fuels?
The report looks at four alternative fuels: hydrogen, ammonia, synthetic fuels (efuels) and biofuels, and examines each option against:
- Equivalent resources that would be required for that option to replace fossil jet fuel,
- Life cycle analysis and non-CO2 environmental impacts,
- Likely costs,
- Modification or replacements needed to implement the option.
It is evident that all alternative fuel options have advantages and challenges and there is no single simple answer to decarbonising aviation.
Main conclusions from the net zero aviation report
- Availability and accessibility of sustainable feedstock for all options is a key challenge.
- Further R&D will be needed in the development of the efficient production, storage and use of green hydrogen, ammonia and efuels.
- Further development of LCAs of all alternative aviation fuels is required which will be critical in clarifying emissions across the entire cycle and highlighting key mitigation opportunities.
- R&D is required to understand and mitigate the non-CO2 climate impacts of all the alternative fuel options.
- A holistic approach with regards to alternative fuel and engine and airframe development will be needed.
- Considerations will have to be made on handling multiple technologies both in the airport and aircraft.
- Staff and crew will need specialised training on handling alternative fuels, and the public will need to be informed about the relevant safety concerns within the airport and aircraft.
Watch as Professor Graham Hutchings FRS, Chair of the Working Group, introduces the report.
https://royalsociety.org/topics-policy/projects/low-carbon-energy-programme/net-zero-aviation-fuels/
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Royal Society report
Green flights not in easy reach, warn scientists
28.2.2023
By Georgina Rannard, Climate and science reporter (BBC)
You may be hoping that guilt-free flying is just around the corner, but scientists warn it is still a long way off.
Plans for climate-friendly flying rest on creating greener jet fuels that have less impact on the environment.
Switching to sustainable fuel is also key to the government’s aim to reach “jet zero” flying by 2050.
But the Royal Society concludes there is currently no single, clear alternative to traditional fuel.
Flying is responsible for 2.4% of global greenhouse gas emissions and 8% of UK emissions. These gases warm the atmosphere, contributing to global warming and climate change.
Demand for flights is expected to increase, and governments and the aviation industry are experimenting with ways to reduce the climate impacts of traditional kerosene fuel.
The authors of the Royal Society report looked at four options for greener fuels to replace the 12.3m tonnes of jet fuel used annually in the UK.
It concluded that none could replace fossil jet fuel in the short term.
Some airlines now use very small amounts of biofuel, largely made from crops. London Heathrow is the largest global user of biofuels but it accounts for just 0.5% of the airport’s fuel.
To produce enough to supply the UK aviation industry would require half of Britain’s farming land, putting pressure on food supplies, the Royal Society says.
Another option is fuel made from hydrogen produced with green electricity. However the UK currently does not generate enough renewable electricity to make enough green hydrogen.
Chart showing emissions from different modes of transport
Another major barrier is that existing plane engines cannot use hydrogen-based fuel.
Ammonia and synthetic fuels are also under consideration, but they need even more green hydrogen and it is unclear if existing planes could use them.
The authors say it remains unclear exactly how much each alternative fuel would reduce the climate impacts of flying.
But they stress that in the long term a successful alternative fuel will probably be developed, but that airplanes and airports will need to be re-designed.
They are calling for more research into sustainable aviation fuel, suggesting that the UK could become a global leader if it invested in solving the problem.
A new fuel needs to be financially viable, safe, usable around the world, and to have high enough energy density to be used on long-distance flights, they say.
But environmental campaigners say the government must also encourage people to fly less.
“Not all aspects of modern life in Western nations have an easy ‘technofix’ for the damage they do to the environment, and nowhere is this truer than for air travel,” suggests Leo Murray, director of innovation at climate charity Possible.
His organisation wants the government to tax frequent flyers, the small number of people who take around 70% of flights from UK airports.
“A Frequent Flyer Levy would target reduced demand amongst the group responsible for most of the environmental damage today, while leaving the annual family holiday untouched,” he says.
https://www.bbc.co.uk/news/science-environment-64788106
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Aviation biofuel would need half of UK agricultural land, report says
The Royal Society said a portfolio of alternative fuels will be required to meet current passenger demand and achieve net zero.
By Danny Halpin (The Independent)
28.2.2023
Replacing jet fuel with biomass would require the UK to give up 50% of its agricultural land to sustain current passenger levels, according to a new report from the Royal Society.
In examining how the aviation industry can reach net zero, the authors said there is no single, clear alternative to kerosene, with biomass requiring huge tracts of land and other options, such as hydrogen, ammonia and synthetic fuels requiring a massive increase in renewable energy production.
The Government is relying on the development of alternative fuels to continue growth in aviation and to allow passengers to enjoy “guilt-free travel”.
In its Jet Zero Strategy published last year it said it wants five “sustainable aviation fuel” plants under construction by 2025.
“The elephant in the room here is, of course, the need to fly less.” Cait Hewitt, AEF.
Figures taken pre-pandemic show UK aviation consumes 12.3 million tonnes of jet fuel and produces 8% of the UK’s greenhouse gas emissions, with the lack of alternative options making it one of the hardest industries to decarbonise.
Producing enough green hydrogen – which is created by splitting water molecules into oxygen and hydrogen with renewably-generated electricity – would require more than doubling or tripling the UK’s renewable capacity.
It would also mean the development of new aircraft and airport infrastructure to store and transport fuel as well as new training and safety regimes.
Professor Graham Hutchings, chair of the report’s working group, said: “The requirements for an alternative to jet fuel, to kerosene, is energy density, has to be sufficient to sustain short and long haul flights, it must be produced globally at scale, it must be cost-competitive and it must be implementable by 2050.”
Using ammonia, which is made using hydrogen, would also require around a tripling of renewable energy capacity and a substantial retrofit of aircraft to accommodate it.
Other forms of fuel which use captured carbon to produce synthetic or electrofuels could be used in existing aircraft engines but would need five to eight times the renewable capacity.
Professor Marcelle McManus of the University of Bath said: “With all of these fuels we need to have new supply chains, new resources and at the scale we need, this is not going to come without difficulties.
“How and where they’re produced will have significant impacts on their impact and their cost.”
She also said that many biofuel sources would not meet the EU’s target for sustainable energy sources – called RED II – because of their production emissions.
The Royal Society authors identified rapeseed, fast-growing poplar trees and miscanthus as energy-providing crops, but because of the amount of land needed, they said, there has been a growing interest in using biowaste such as used cooking oil.
They said the UK is “highly reliant” on importing raw material for biofuel, known as feedstocks, with 423 million litres of used cooking oil imported from China alone in 2021.
Converting waste from the 250 million litres of vegetable oil produced in the UK would produce only 0.3 to 0.6% of the UK’s annual jet fuel needs.
A spokesperson from the Department for Transport said: “The UK’s Sustainable Aviation Fuels programme is one of the most comprehensive in the world.
“Our Jet Zero Strategy sets out how we can achieve net zero emissions from UK aviation by 2050, without directly limiting demand for aviation. Sustainable aviation fuels and hydrogen are key elements of this, and we will ensure that there is no impact on food crops.”
A spokesperson for Airlines UK, the industry’s trade body, added: “There is no magic bullet, but by modernising airspace to make flying more efficient, by introducing new zero-emission technology like hydrogen aircraft and by upscaling the use of sustainable aviation fuels this decade, it can be achieved.
“Critically, the UK does have sufficient feedstocks for sustainable fuels, which would be drawn initially from household, commercial, agricultural and forestry waste and waste industrial gases – and do not compete with food crops.”
The report also said that replacing kerosene may not completely stop planes from warming the Earth’s climate.
Contrails, which are caused by water vapour freezing on soot particles from a plane’s engine, can sometimes spread into cirrus clouds and then warm the atmosphere by trapping infrared radiation.
It is thought that up to two-thirds of the climate-warming effect from aviation comes from non-CO2 sources like contrails, though there is a wide degree of uncertainty about this.
Cait Hewitt, policy director at Aviation Environment Federation, which campaigns on aviation’s environmental impacts, said: “The elephant in the room here is of, course, the need to fly less.
“One area that would really benefit now from some Government-funded research is how to deliver better standards of living, continued connectivity for businesses, and sustainable employment for the aviation workforce without the continued growth of flying.
“Tax cuts for domestic tourism and leisure and promotion of alternatives to in-person business flights would be good places to start.”
The Climate Change Committee, which advises the Government on how to reach net zero, said in its sixth carbon budget that passenger demand should not rise more than 25% by 2050 from its pre-pandemic levels.
At its current rate, demand is expected to grow by 65% without any further airport expansions, though Bristol Airport was recently granted permission in the High Court to expand and five others have similar plans.
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Delayed take-off: Royal Society questions whether sustainable jet fuels can meet soaring demand
By Stuart Stone (Business Green)
28 February 2023
Report warns meeting the UK’s net zero aviation ambitions through sustainable fuels could require vast quantities of agricultural land or renewable electricity
Producing sufficient sustainable aviation fuel (SAF) to honour the UK’s net zero aviation pledges would require almost half the country’s agricultural land or around triple the renewable electricity generation achieved in 2020 to maintain current numbers of flights, the Royal Society has warned.
The science academy will today publish a major new, titled Net zero aviation fuels: resource requirements and environmental impacts, which cautions there is no single, clear, sustainable alternative to jet fuel able to support flying at today’s scale.
The findings could represent a major blow to the government’s so-called Jet Zero strategy to deliver net zero emissions from the aviation industry, which has resisted calls from campaigners to introduce policies to curb the number of flights. Ministers have instead argued new technologies such as SAFs and ultimately zero emission aerospace technologies can allow the aviation industry to deliver net zero emissions, even as the number of flights continues to increase.
According to data from the Office for National Statistics, there are on average around 4,000 flights to, from, and within the UK at present, accounting for eight per cent of nationwide greenhouse gas emissions in 2019. Additionally, CO2 emissions from global aviation increased from 600 million tonnes in 2020 to around 720 million in 2021.
The report from the Royal Society analysed a number of different avenues for decarbonising flights, including green hydrogen, biofuel, ammonia and synthetic fuels. It explored the resource availability, research requirements, likely costs, life-cycle impacts, infrastructure requirements, and outstanding research questions across the different approaches.
It concludes that the various technologies offer different pros and cons. For example, biofuels require little aircraft modification or additional infrastructure, with the resulting CO2 largely absorbed through the biomass feedstocks that makes the fuels, while hydrogen and ammonia fuelled planes produce no CO2 but demand “substantial” upgrades. In contrast, synthetic fuels produce some CO2, but require fewer modifications.
But the Royal Society estimates that meeting existing aviation demand entirely with energy crops would require around half of the 16.8 million hectares comprising the UK’s utilised agricultural area – around 69 per cent of the total area of the UK and an area larger than Denmark or the Netherlands.
It also forecasts that sustainably producing sufficient green hydrogen fuel would require just shy of three-and-a-half times the UK’s 2020 wind and solar electricity generation – while ammonia-based and synthetic fuels would respectively reqiure a four-fold or eight-fold increase in renewables generation.
“Research and innovation are vital tools for the delivery of net zero,” said Professor Graham Hutchings, regius professor of Chemistry, Cardiff University, and chair of the report working group. “But we need to be very clear about the strengths, limitations, and challenges that must be addressed and overcome if we are to scale up the required new technologies in a few short decades.”
Professor Marcelle McManus, director of the Institute for Sustainability at the University of Bath and a working group member, added that how fossil fuel alternatives are produced – and the tracking of associated emissions – will prove critical to determining which decarbonisation pathway is most effective.
“We need consistency, and we need to apply this globally, because adopting any of these new technologies will create demands and pressures for land, renewable energy or other products that may have knock on environmental or economic effects,” she said.
The report is likely to be seized upon by environmental campaigners as further evidence of the need to take steps to curb the number of flights in the near term, while new low and zero emission aviation technologies are tested and deployed at scale.
However, the aviation industry is likely to counter that emerging technologies and falling renewables costs do provide a route for it to decarbonise flights across the industry. A separate industry-backed analysis from the Sustainable Aviation group of companies and consultancy ICF last year concluded the UK has access to sufficient sustainable feedstocks to deliver on a proposed mandate for airlines to use at least 10 per cent sustainable aviation fuel by 2030 – before then scaling up the nascent industry further to help achieve net zero emissions by 2050.
Advocates of SAFs maintain that emerging alternative feedstocks, such as captured industrial gases, algaes, and waste materials, could be used to deliver sustainable fuels at scale without the land use impacts associated with energy crops.
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