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Could Aviation Be Decarbonised and Become Sustainable?
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Aviation opens up the world. It connects people, powers tourism, and drives global business. But it also comes with a heavy climate cost.
Although air travel accounts for just 2.5% of global CO2 emissions, its overall contribution to global warming is closer to 4% when you factor in other pollutants like contrails and nitrogen oxides. And while planes have become more efficient over time, rising demand is canceling out those gains.
“ Passenger numbers are climbing fast, nearly 10 billion trips are expected in 2025 alone, a 6.7% yearly increase, meaning aviation’s emissions are on a clear upward trajectory. ”
So the question is: can we keep flying without costing the Earth? Can aviation really be decarbonised, and if so, how soon?
What you’ll learn in this article
- Why aviation is particularly harmful to the environment
- What makes flying different from other forms of transport
- The alternative fuels that could change the game, and their limitations
- What’s being done today to reduce emissions
- What individuals and companies can do to help
The aviation industry and carbon emissions: a quick overview
Compared to road transport, aviation might seem like a minor offender. But appearances can be misleading.
Road vehicles are the biggest contributor to transport-related emissions, accounting for nearly 75% of global transport CO₂ in 2022. In contrast, aviation contributes just 10%. Yet aviation’s emissions are growing faster, and far fewer people fly than drive.
| Transport mode | Share of global transport CO₂ | Emissions trend |
|---|---|---|
|
Road (cars, trucks)
|
~75% | Slowing with EV uptake |
|
Aviation
|
~10% | Rapid growth |
|
Shipping
|
~12% | Moderate growth |
|
Rail
|
~1% | Declining in many areas |
Despite serving a much smaller segment of the population, aviation punches far above its weight in terms of emissions, especially on a per-passenger basis.
“ A single return flight from London to New York emits nearly 2 tonnes of CO₂ per passenger - more than the total annual emissions of an average person in over 85 countries. ”
So while road transport remains the top emitter overall, it’s aviation that stands out for its emissions inequality, and the growing urgency to rein in its impact.
Why is flying bad for the environment?
Most people know that planes burn fossil fuels and emit carbon dioxide (CO2), but what many don’t realise is that CO2 is just part of aviation’s climate impact.
“ In fact, more than two-thirds of aviation’s total warming effect comes from non-CO2 emissions, such as water vapour, nitrogen oxides (NOₓ), carbon monoxide (CO), and soot particles ”
The full climate impact of flying:
Aviation contributes to global warming in multiple ways:
CO₂ emissions
From burning jet fuel
Carbon dioxide released during flight remains in the atmosphere for centuries, driving long-term warming.
Water vapour
Creates contrails and cirrus clouds
Contrails trap infrared radiation, contributing to warming through induced cloudiness.
Nitrogen oxides (NOₓ)
Alter atmospheric chemistry
NOₓ increases ozone levels at high altitude, a powerful short-lived greenhouse gas.
Black carbon & soot
Absorb sunlight and alter clouds
Soot particles warm the atmosphere and affect cloud formation, increasing radiative forcing.
Contrails & cloudiness
Amplify warming effect
Research shows contrails may contribute more to warming than aviation CO₂ itself.
Why contrails matter
Those white streaks in the sky? They're not just harmless vapour.
Contrails form when hot, moist air from jet engines mixes with cold air at high altitudes. This creates ice crystals that cluster around soot particles, forming linear clouds that can linger for hours. These clouds trap outgoing infrared radiation from the Earth’s surface, effectively acting like a blanket.
“ Recent research suggests that contrail-induced cirrus clouds may rival or surpass CO2 emissions from aviation. ”
Is sustainable flying really possible?
We know aviation is bad for the environment, and with passenger demand rising year on year, the industry’s carbon footprint is only getting bigger. So, where does that leave us? Can we still fly in a way that aligns with climate goals?
Many people hope that technological innovation will deliver guilt-free flying. But how realistic is that hope?
To decarbonise aviation, we need to transition away from fossil-based jet fuel and adopt sustainable aviation fuels (SAFs) that emit fewer greenhouse gases. But this is easier said than done.
The aviation sector faces unique challenges:
Aircraft have long lifespans — typically 20 to 30 years — which makes fleet turnover a slow and expensive process.
Planes require high energy-density fuel. Most alternatives used in cars or trucks simply don’t pack enough power for flight.
Infrastructure and aviation safety regulations are complex and costly to adapt — slowing down the rollout of new fuel types.
A recent Royal Society review of alternative jet fuels - including hydrogen, ammonia, synthetic fuels, and biofuels - found that while each holds promise, none are currently ready to replace conventional jet fuel at scale.
So, what are these alternatives, and what’s stopping them from taking off?
Let’s take a closer look at the leading options for sustainable aviation fuel and the roadblocks they face.
Hydrogen
Hydrogen is widely seen as the most promising candidate to decarbonise aviation. It burns cleanly and has the potential to cut the climate impact of flying by as much as 50–75%. However, using hydrogen as jet fuel would require major changes to aircraft design and fuel storage, as well as investment into new infrastructure across airports.
Airbus is leading the way with its ZEROe programme and aims to launch the world’s first hydrogen-powered commercial aircraft by 2035. Yet even this target is seen as ambitious, and most analysts expect commercial readiness to lag behind that timeline, particularly for long-haul flights.
✅ Key benefits
💨 Zero CO₂ emissions at point of use
🛫 Could reduce total climate impact by up to 90%
✈️ Airbus is aiming to launch hydrogen aircraft by 2035
⚠️ Remaining challenges
❄️ Requires cryogenic storage at –253 °C
🔧 Aircraft need redesigns and new airport refuelling systems
💰 Limited supply of green hydrogen and high production costs
Ammonia
Ammonia is emerging as a promising hydrogen-based fuel for aviation. Already widely produced (mainly for fertiliser), ammonia has around 49% more energy per litre than liquid hydrogen, making it easier to transport and store. If synthesised using renewable energy and green hydrogen, it can offer a carbon-free alternative to kerosene.
It also has an edge when it comes to climate impact. Unlike kerosene and even hydrogen, ammonia combustion doesn’t produce soot, which means it could significantly reduce contrail formation — one of the biggest non-CO2 drivers of aviation-induced warming.
But challenges remain. Ammonia is toxic and corrosive, requiring strict safety measures and new handling infrastructure. And while it avoids CO2, it can still generate nitrogen oxides (NOₓ), meaning it’s not a perfect solution. Retrofitting aircraft for ammonia combustion is still in the very early stages, and experts place commercialisation around ten years behind hydrogen.
✅ Key benefits
🟢 Potential for zero CO₂ emissions when synthesised from renewable-powered H₂ and N₂
🌫️ Could dramatically reduce contrail formation, as ammonia combustion doesn’t produce soot
⚠️ Remaining challenges
☣️ Toxic and corrosive — requires new safe-handling infrastructure
📦 Bulkier storage than kerosene, reducing aircraft range and payload
💨 Emits NOₓ during combustion, requiring advanced engine design for mitigation
Synthetic (drop-in) Fuels
“ Synthetic fuels, or e-fuels, are considered one of the most practical short-term options for decarbonising aviation. Unlike hydrogen or ammonia, they don’t require redesigning aircraft or building new fueling infrastructure. That’s because they’re “drop-in” fuels - compatible with current engines and refueling systems. ”
These fuels are made by combining hydrogen (typically from water electrolysis) with captured carbon dioxide, using renewable energy. When both the hydrogen is produced from green electricity and the CO2 is captured directly from the atmosphere, the fuel has the potential to be close to carbon neutral. However, the technology to capture and reuse atmospheric CO₂ at scale is still in its early stages, and will require major advancements in efficiency and cost to become widespread.
Synthetic fuels also come with major trade-offs. Producing them is energy-intensive and expensive (often up to eight times the cost of conventional kerosene). And current blending limits only allow 50% synthetic fuel in most commercial flights, limiting their benefits.
Despite this, synthetic fuels are currently the most scalable low-carbon option available, and many airlines are already investing in production facilities and long-term procurement agreements.
✅ Key benefits
✈️ Compatible with existing aircraft and fueling infrastructure
🌍 Can be nearly carbon neutral when produced with renewable energy and captured CO₂
💡 Already being used in some commercial flights (blended with conventional fuel)
⚠️ Remaining challenges
💰 High production cost — up to 8x more than conventional jet fuel
🔄 Current regulations only permit a 50% blend, limiting short-term impact
⚡ Requires significant renewable energy input and CO₂ capture infrastructure
Biofuels
Biofuels, often derived from crops or waste products, are already being blended in small amounts with conventional jet fuel. Heathrow, for example, is currently the largest user of aviation biofuels globally, though they still account for less than 1% of its total fuel use.
While biofuels are technically compatible with existing aircraft and fueling infrastructure, scaling their use presents major environmental and logistical challenges. First-generation biofuels, made from food crops like corn or soy, can drive deforestation, increase food prices, and compete with land needed for agriculture or biodiversity.
Even second-generation biofuels, produced from waste or non-food biomass, face scalability issues. According to Carbon Brief, if the UK aviation industry were to run entirely on biofuels, it’s estimated that up to 50% of all UK farmland would need to be dedicated to fuel production - a trade-off that raises serious sustainability questions.
✅ Key benefits
🔧 Compatible with current engines and infrastructure
🌱 Potential to reduce lifecycle emissions compared to fossil jet fuel
🍟 Waste-based biofuels avoid food vs. fuel conflicts
⚠️ Remaining challenges
🌾 Limited supply of sustainable feedstocks
🌍 Land-use impacts and potential competition with food crops
🌳 Not carbon neutral when deforestation or fertiliser use is factored in
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What’s next for sustainable aviation?
“ There’s no denying it: aviation remains one of the hardest sectors to decarbonise. There’s currently no single fuel or technology that ticks all the boxes - scalable, affordable, safe, and ready for long-haul commercial flights. ”
But while a perfect solution doesn’t yet exist, momentum is building.
🚀 Momentum is building
- Hydrogen-powered aircraft in development (e.g. Airbus ZEROe)
- Airlines signing long-term synthetic fuel deals
- Airports investing in hydrogen-ready infrastructure
- Electric aircraft trials for short-haul flights
🏛️ Policy is driving progress
- ReFuelEU Aviation: 70% SAF blending target by 2050
- Tax credits and SAF subsidies in US & UK
- Increased investor confidence in SAF projects
⏳ Short-term focus
- Synthetic and biofuels are "drop-in" compatible
- No redesign of aircraft required
- Challenges: high costs, scalability, land use
- Most viable way to cut emissions now
A long-haul transition
Looking further ahead, the path to sustainable aviation is likely to be a mix of solutions:
Synthetic fuels
for existing fleets
Hydrogen or ammonia
for new aircraft
Electrification
for short-haul routes
Operational efficiencies
to reduce fuel burn
Each of these technologies has a role to play, but scaling them will take time, investment, and political will.
The sky isn't the limit
The transition won’t happen overnight. But thanks to rising climate pressure, growing investment, and rapidly evolving technology, sustainable aviation is finally starting to take off.
The future of flight may not be fully green yet, but it’s no longer grounded!
What can we do in the meantime?
While the aviation sector works toward long-term decarbonisation, the reality is that most of us will still need to fly, whether for work, family, or pleasure. But that doesn’t mean we’re powerless in the face of aviation’s climate impact. Until cleaner fuels and new aircraft technologies scale up, individuals and businesses can take meaningful steps to reduce the footprint of flying today.
Here are a few practical, low-carbon actions we can take:
| Action | Why it matters |
|---|---|
|
Take the train (or bus)
|
Short-haul flights are the most carbon-intensive form of travel. Trains emit far less – for example, a Paris–London Eurostar trip emits ~80% less CO₂ than flying. |
|
Fly economy instead of business
|
Business class takes up more space and resources, making it up to three times more carbon-intensive than economy class. |
|
Offset your flight emissions
|
Offsets support climate projects like reforestation or renewable energy. They’re helpful, but not a true substitute for cutting emissions at the source. |
|
Choose virtual meetings
|
Many work trips can be replaced with a video call — saving money and cutting emissions instantly. Physical presence is rarely essential. |
Even small changes can help lower your travel footprint, and collectively, they send a strong signal to airlines, governments, and innovators that cleaner aviation needs to be a priority.
Close
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Greenly makes sustainability measurable, manageable – and meaningful. Get in touch today to find out more.
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