Flying, for business or pleasure, has long been seen as one of the biggest carbon villains. As airports gear up again after COVID-19, it's clear not every business wants to keep meetings online and not all holiday makers want to settle for a staycation.
But what if we could fly without the guilt? Tom Heap meets some of the pioneers of zero carbon flight: hitching a ride with Harbour Air in Canada who have retrofitted one of their planes to fly on electric battery power; visiting the equivalent of the Batcave with a Bristol company making EVTOLs - electic vertical take off and landing vehicles - which could see us zipping between cities; and asking about the use of sustainable aviation fuels. Dr Tamsin Edwards joins him to discuss how much carbon dioxide - and more - this could potentially save.
Listen now on BBC Radio 4
What our experts say
We asked Society Fellows Dr Andy Jefferson, Programme Director at Sustainable Aviation, and Tim Johnson, Director at the Aviation Environment Federation, to offer observations on the potential of decarbonising aviation through sustainable aviation fuels, electric aircraft and hydrogen fuel cells in reducing carbon emissions. Their points take some of the themes of the programme a step further.
Dr Andy Jefferson
Aviation now has a plan to decarbonise and companies across the industry are increasingly making net zero commitments. The challenge is to ensure the plan gets delivered! Options to address aviation carbon emissions fall into four key categories.
1. Operate smarter flights
Improving flight efficiency by modernising airspace and making smarter use of aircraft and air traffic management modelling, forecasting and navigation systems. This offers immediate emission reductions by enabling avoidance of congestion hot spots, minimising fuel burn and using real time weather information to minimise the adverse effects of flying into headwinds or in areas of the atmosphere that encourage contrail formation.
2. Introduce new, more efficient, aircraft technology
Initially by replacing current aircraft and engines with more efficient ones, reducing fuel usage by around 20% compared to the aircraft they replace.
Then, by from the mid 2030s, switching to new aircraft technology such as electric and hydrogen planes. The industry ambition is for these small concept aircraft to be developed further such as in the Airbus zeroE proposals. In the UK, much of this work is being explored through the joint UK aviation industry and UK Government Aerospace Growth Partnership and Fly Zero programme through the Aerospace Technology Institute.
3. Switch to using lower carbon or carbon neutral sustainable aviation fuels (SAF)
This is likely to happen in two stages. Initially the UK aviation industry expects these SAF fuels to reduce flight emissions by 80% compared to using fossil jet fuel by using residual landfill, and agricultural and forestry wastes. In the future though, there are exciting opportunities for SAF to be made from green hydrogen, captured carbon and renewable energy, reducing emissions completely. If the SAF production facility is also linked with a carbon capture and storage facility the SAF could even be carbon negative for emissions.
Sustainable Aviation published work by independent consultants E4Tech looking at waste feedstock availability for SAF (Appendix 1, pp. 38-39). This is based on specific sustainability criteria (pp. 10) which restricts the use of palm oil based products or risks using land that could otherwise grow crops to feed society.
In the UK, the aviation industry believes these SAF opportunities can produce 4.5 million tonnes of SAF by 2050 (around a third of expected UK aviation fuel demand by then). This relates to an emissions saving of over 14 metric tonnes of carbon dioxide equivalent (MtCO2eq). European and global aviation studies also highlight significant emission reduction potential from the use of SAF. The immediate aim is for the first three UK SAF plants to be operational by 2025. Other SAF plants are already in operation or close to it in the US and Europe.
4. Invest in carbon removal outside the aviation sector (market-based measures)
Aviation has been recognised as one of the hardest to abate sectors going forwards by the UK Committee on Climate Change (CCC) in their sixth carbon budget advice. The CCC and Sustainable Aviation both recommend that ‘residual’ carbon emissions (those left after technology, flight efficiency and SAF have been used) need to be met through investment in carbon removal solutions outside the aviation industry. The CCC recommends buying carbon removal in the UK, whilst the UK aviation industry say this needs to be met through recognised carbon removal schemes in the UK and beyond.
EVTO - electic vertical take off and landing vehicle (Image: BBC)
Tim Johnson
In 2019, the airline trade association IATA (the International Air Transport Association) reported that civil aviation globally emitted 915 million tonnes carbon dioxide (MtCO2), a record year and more than twice as much as the total emissions from the entire UK economy. Worldwide aviation fuel use is forecast to increase two to three times between now and 2050 (reflecting fast growth rates in other parts of the world).
It was also a record year in the UK: civil aviation emissions in the UK in 2019, as reported in the official UK GHG national inventory, were 38.4MtCO2. This comprised 1.4MtCO2 from domestic flights within the UK and 37MtCO2 from flights departing the UK for international destinations. Government forecasts predict that if passenger numbers increase by a further 66% by 2050 (compared with 2016), with airports making best use of their capacity and adding a third runway at Heathrow, CO2 emissions would rise to around 40.8MtCO2 (this includes aircraft efficiency gains and small amounts of sustainable aviation fuels - 5% by volume). But with other UK airports currently likely to grow beyond these forecasts, AEF’s extrapolation of the Government’s data suggests the 2050 figure could be as high as 45.7MtCO2 if all plans are approved.
New technologies, the higher uptake of SAF, and policies to manage demand have the potential to reduce these projected increases in aviation emissions. The Government published a consultation on net zero aviation in July 2021 in which it tries to put numbers to likely CO2 reductions from these initiatives. For new zero emission aircraft (using hydrogen or electric propulsion) it predicts a reduction of 2-7MtCO2 by 2050, and 2-20 MtCO2 for sustainable aviation fuels. The wide range illustrates the uncertainty. With ‘high ambition’ for these technologies and fuels, the Government believes it may be possible to reduce aviation emissions in 2050 to 21MtCO2. The Climate Change Committee broadly agrees that emissions could be around this level (its analysis suggests 23MtCO2) but with the added measure of limiting passenger demand to a 25% increase on 2018 levels (significantly less than Government’s projection). Government, CCC and industry projections all agree that in-sector emission reductions alone will be insufficient to get the sector to net zero, and that large scale greenhouse gas removals will be necessary to balance the sector’s residual emissions. Greenhouse gas removals differ from many offset projects which claim credit for avoiding the release of emissions. Avoided emissions do not change the amount of CO2 in the atmosphere.
What are the limiting factors?
Dr Andy Jefferson
Consistent and sustained policy support
Aviation operates in a globally competitive market beyond the boundaries of national borders. This means the best way to reduce aviation emissions is through global policies consistently applied by all countries.
In the UK, the industry is committed to working with the Government and others to improve policy support and is encouraged by the recent formation of the UK Jet Zero Council as a key enabler to this.
Sustainable Aviation has set out a number of clear policy support ‘asks’ of the UK Government required by the aviation industry in their latest announcement of interim targets to net zero 2050.
A positive example for SAF is the US Federal Administration making funds directly available to support SAF development. The challenge for the UK, from policy moves in the US and Europe, is the drawing of skills and expertise away from the UK. The industry is working with the UK government to resolve this and hopes substantive progress will be made later this year.
Limited time for delivering solutions
It will take time to develop the new technology aircraft, especially the battery and hydrogen planes. Whilst 6-20 seater aircraft may be developed in the next five years, the mid 2030s is when the industry expects these technologies to produce a short haul commercial scale aircraft (100-200 seater) – see Airbus zeroE. These aircraft then need to be bought and phased into airline fleets for short haul flights, to and from Europe in the UK’s case, which will take some further time.
For SAF the first UK plant has received planning permission but because of weak/limited UK policy support this facility is not expected to be operational before 2026. Further UK SAF plants are also now being explored (see Lanzatech and Fulcrum BioEnergy and Essar).
This time lag does not prevent net zero 2050 emissions being met but does mean there will be a varying mix of mitigation measures effective at any one time. This is depicted in the Sustainable Aviation 2020 Decarbonisation Road-Map.
Access to finance
It will take billions of pounds to decarbonise aviation. COVID-19 has impacted both governments and the industry’s ability to self-fund this. However, there is substantial global private sector investment looking to invest in low carbon/green recovery projects now. The aviation industry understands the key to securing this global investment is strong Government policy support as well as ‘market demand’ from users (e.g. the aviation industry). The industry is already providing the market demand signal through making net zero commitments.
Increasing sustainability requirements from investors
Most aviation companies now face these investor challenges. It will be important to ensure financial investment tools drive emission reductions as effectively as possible and avoid an unintended consequences such as preventing finance for new innovation solutions because they don’t or can’t meet a fix set of assessment criteria.
Volocopter (Image: Spielvogel, CC BY-SA 4.0 via Wikimedia Commons)
Tim Johnson
There are three zero carbon pathways for aviation on the horizon - electrification, hydrogen, and synthetic fuels made using captured carbon (the latter still emits carbon when combusted but this is balanced by the carbon removed from the atmosphere during production – in effect, a closed loop system). Other ‘sustainable aviation fuels’ include biofuels but most only achieve around a 60% lifecycle reduction in carbon on average, and using waste materials is unlikely to be scalable.
Of the three pathways, limiting factors include:
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Electrification: Battery size and weight is a limiting factor today, confining applications to up to nine-seater aircraft. As battery technology improves, not only in terms of size but in performance (most batteries will only be able to hold a charge for so many cycles before performance begins to suffer), it is feasible to think this technology could scale this up to aircraft with around 30 seats in the medium term (perhaps sufficient to meet the Government’s pledge to decarbonise UK domestic aviation by 2040). However, there is a consensus that we are unlikely to have short-haul or long-haul electric aircraft carrying more than 100 passengers much before 2050. And we are going to need the renewable energy to power the fleet, as well as thinking about how to rapidly charge aircraft at airports and how to recycle batteries.
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Hydrogen: We need to think carefully about how we produce hydrogen: the focus should be on using green hydrogen (produced using water and renewable energy) rather than blue hydrogen made from fossil fuels. Developing hydrogen will require a big investment in infrastructure. Global coordination is required to ensure states adopt this technology at the same time which may require significant investment and capacity building in developing economies.
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Synthetic fuels (also known as power to liquids, e-fuels): Manufacturing synthetic fuels is energy intensive and will require significant amounts of surplus renewable energy for direct air capture of carbon and the conversion process which uses hydrogen to create a hydrocarbon fuel. Direct air capture and hydrogen production need to happen at scale but they are currently limited to a few pilot schemes and are expensive.
Cost will be an initial barrier to all three approaches, especially as kerosene is relatively inexpensive and is untaxed. The sector also lacks strong carbon pricing signals to accelerate the transition (the UN’s CORSIA scheme requires the emissions growth above 2019 levels to be offset, although this level is unlikely to be reached for several years due to the effects of the Covid pandemic). Flights departing the UK for EEA destinations are included in the UK’s emissions trading scheme.
What are the co-benefits?
Dr Andy Jefferson
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Maintaining the ability for society to travel – to meet friends and family, to have well earnt holidays as well as trade and do business.
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Securing and strengthening jobs, skills and economies across the globe that rely on aviation and travel. Sustainable Aviation last summarised this in its 2016 UK Aviation Industry Socio-Economic Report.
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Supporting and encouraging low carbon or negative carbon solutions that give benefits beyond just aviation, such as, carbon removal and SAF.
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Creating new jobs and economic benefits for countries investing in low carbon innovations, for example, independent work on SAF for Sustainable Aviation suggest 14 SAF plants in the UK by 2035 will create 6,500 new jobs and contribute an additional £1 billion to the UK economy.
Tim Johnson
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Supporting green jobs in battery, hydrogen and direct air capture industries.
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Electric planes could be quieter on take-off bringing noise benefits to communities around airports and living under flightpaths (noise on landing may not be reduced as airframe noise, rather than engine noise, is dominant).
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Electric planes will not produce contrails or emissions of nitrogen oxides (NOx) which have a net warming impact on the atmosphere. The absence of NOx will also reduce local air pollution.
Are there any potential negative impacts of this idea?
Dr Andy Jefferson
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Risk of failing to deliver on decarbonising aviation and subsequent climate change impacts.
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For the battery electric vertical take-off and landing (EVTOL) concepts looked at, there are risks in use of scare materials to make the batteries and e-waste issues at their end of life. Aerospace projects such as Fly Zero are looking at this to minimise these negative impacts.
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Fear of failure perceptions which may be constraining opportunities: if there is a collective view that decarbonising aviation is all ‘a bit too hard’ it could lead to a conclusion that the only way out is to stop or severely cut flying. The aviation industry strongly disagrees with this viewpoint because it is close to the technology opportunities and has a clear plan for how these can decarbonise aviation. Successfully communicating and sharing this understanding with others, and working in partnership to deliver it, will be the key to future success for aviation and can overcome current fears about failure in this area.
Tim Johnson
Hydrogen planes will produce water vapour at altitude which has a warming impact. Currently, aviation’s contribution to global warming is three times higher than that from its carbon emissions alone, with two thirds of the impact coming from water vapour and aerosols, the formation of contrail cirrus clouds, and changes to atmospheric concentrations of methane and ozone. All new technologies need to consider the net climate impact and not just carbon emissions.
Further reading
About the series
39 Ways to Save the Planet is a new radio series by BBC Radio 4 developed in partnership with the Society and broadcast in 2021. It showcases 39 ideas to relieve the stress that climate change is placing on the Earth. In each 15 minute episode Tom Heap and Dr Tamsin Edwards meet the people behind a fresh and fascinating idea to cut the carbon.
Programme website
Over the course of 2021, the Society will be producing events and digital content to accompany the series.