A century after the first commercial flight, aviation has become a fixture of global transport… and global emissions. It has allowed us to connect the world in ways never seen and has contributed immensely to global economic and social development.

However, aviation produces approximately 1.9% of annual carbon emissions. Approximately half of the total cumulative emissions of CO2 were generated in the last 20 years alone, attributed largely to the expansion of the number of flights, number of routes and fleet sizes.

Two-thirds of air travel’s impact is attributed to non-carbon dioxide emissions such as nitrogen oxide (NOx) emissions, and the effect of contrails and contrail cirrus—clouds of ice crystals created by aircraft jet engines at high altitude.

The commercial aviation sector has also been responsible for increased noise levels, air pollution and environmental damage, especially in the vicinity of airports as well as ineffective waste management. By achieving efficient air travel, we can continue to reap the benefits of globalisation without harming the Earth’s climate.

How do we achieve sustainable aviation?

There are four main routes, outlined in the image below. In preparation for the workshop this month, our brilliant research team have explored lots of potential solutions within these avenues, so we’ll highlight a few of these here:

It’s all about technology! 

Technological improvements include adopting the latest and most fuel-efficient aircraft, retrofitting existing aircraft and retiring older aircraft early, among others.

A number of ongoing projects in electric or hybrid-electric aircraft technology have been identified globally – most of these, target an entry-in-service date between 2020 and 2030, and some are already commercially available!

Aircraft could also be powered by hydrogen, either from direct combustion (hydrogen turbine) or via a fuel cell. Hydrogen emits no CO2 during the combustion process and allows for significant reduction of other elements that drive global warming, such as soot, nitrogen oxides, and high-altitude water vapour. 

What about infrastructure?

The International Civil Aviation Organisation (ICAO) has developed plans to optimise communication, navigation and surveillance (CNS) and air transport management (ATM) to reduce fuel burn and greenhouse gas emissions (GHGs). 

Airlines are also working to align emissions cuts with their bottom-line interests. Fuel typically accounts for 20-30% of operational costs—one of the largest single-cost items. Therefore, providers have an intrinsic motivation for adopting more fuel-efficient flying, taxiing, and airport operations. Some of them are equally turning to their employees’ behaviours and mindsets related to fuel. 

Have you heard about sustainable aviation fuels (SAF)?

Figure 1: SAF (ICAO, 2017)

Sustainable aviation fuels (SAF) have great potential for securing the sustainable growth of air travel as they could reduce CO2 emissions by around 80% compared with fossil fuels, without the need to radically change the fuel supply systems or engines of aircraft. 

Whilst the use of Municipal Solid Waste could help address problems and costs associated with waste management in urban centres, when produced from crops, biofuels can be subject to sustainability concerns, including competition with food and water, land-use changes, among others. CO2 emissions can still be generated during SAF production, therefore this should not be considered a net-zero approach.

How do we ensure scale and competitiveness?

There are a variety of economic measures that could make a positive difference. One of these is applying a carbon tax on aviation emissions, although this needs to be sufficiently high and combined with other measures. 

An alternative may be the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) – the first global market-based measures scheme in any sector, to address the increase in total CO2 emissions from international aviation. CORSIA represents a cooperative approach that moves away from a “patchwork” of regulatory initiatives and allows to offset any hard-to-curb CO2 emissions.

It remains to be seen how effective the scheme will be, taking into account the early stages of the scheme, and the many uncertainties that remain to be resolved. It should also be noted that offsetting as a longer-term solution is controversial. Some critics view it as an attempt at greenwashing and others believe that it might relieve the pressure on buyers to reduce their emissions in other ways.

Why is sustainable aviation still out of reach? 

Lack of ownership

Aviation is seen as international in nature; therefore, it has tended to fall through the net when it comes to climate change policy. The Kyoto Protocol, the landmark global climate deal agreed in 1997, left out emissions from international aviation on the basis of disagreement about how best to allocate them to individual states. While a scheme to offset emissions from 2020 onwards (i.e. CORSIA) has now been agreed, this has not been designed to be compatible with the ambitious Paris Agreement on climate change, therefore further policy improvement is required.

We need to collaborate

More and engaged stakeholders are needed for the increase of efficiencies and the development and adoption of sustainable aviation fuels.

First, airlines could build and orchestrate a consortium of stakeholders that includes technology providers and oil companies to drive demand and help bridge the cost gap. For example, airlines could commit to buying SAF at a predefined price, or at a price differential to traditional jet fuel, which would eliminate market risks for fuel suppliers.

Next, airlines could work with B2B customers willing to pay a premium for the opportunity to decarbonize their employees’ footprints. For individual customers, airlines could use loyalty-program rewards as incentives to offset CO2 through SAF use. Airline alliances could take a more active role in promoting the benefits of code-sharing to increase the load factor on any given flight.

Who pays? 

The price of SAF could be 1.5-3 times the price of conventional aviation fuels (CAF), which is a clear economic burden for airlines. Financial institutions should provide venture capital for developing new aircraft technology and SAF production facilities and new infrastructure that allows for the anticipated cost savings. Building a coalition of airlines could increase the required volume, resulting in scale effects.

Let’s get inventive!

The use of fully electric or hydrogen-powered aircraft carrying more than 100 passengers appears unlikely within the next 30 years or longer. Given the lower energy density of batteries compared to fuels, aircraft would need to carry more than 50 kg of battery weight (with today’s technology) to replace one kilogram of kerosene. Because battery weight wouldn’t burn off the way fuel does, carrying that weight for an entire flight would require energy, creating a penalty for longer flights in particular. Similarly, liquified hydrogen would require four times the volume of kerosene, so its use would reduce space for customers or cargo.

What’s been happening around the world?

There are lots of positive stories from all over the globe! Here are a few of them…

Institutions and governments are announcing policies on CO2 or SAF: Norway has mandated that 0.5 percent of aviation fuel in the country must be sustainable from 2020, while Sweden has decided to introduce a green tax on international travel.

The International Air Transport Association (IATA) has launched a trading platform for airlines and other companies in the aviation industry to buy carbon offsets. The Aviation Carbon Exchange will feature projects that reduce carbon emissions through forestry, wind energy development and ecosystem protection. 

Jet Zero Council is a partnership between the UK government and industry to bring together ministers and C-Suite stakeholders, with the aim of delivering zero-emission transatlantic flights within a generation.

UK’s environmental charity We Are Possible has proposed the creation of an eco-tax / frequent flyer levy to actively reduce the number of unnecessary flights taken.

Essar Oil (UK) has joined forces with Fulcrum BioEnergy facility to convert non-recyclable household waste into sustainable aviation fuel (SAF) for use by airlines operating at UK airports. 

British Airways has announced an investment in a commercial sustainable aviation fuel (SAF) plant that should start producing fuel by the end of 2022. The airline, which has a net zero target for 2050, is working with SAF technology provider and producer LanzaJet. 

United Airlines is making a multimillion-dollar investment into technology that removes carbon dioxide from the atmosphere. It will support the construction of an industrial-sized plant expected to sequester 1 million tons of carbon dioxide—the equivalent capability of 40 million trees—and permanently store it underground. The airline is also partnering with air mobility company Archer to develop and eventually use aircraft with electric motors that would serve as “air taxis” in urban markets.

Can we make a difference?

The importance of personal actions

Choosing to fly less can reduce an individual’s carbon pollution by up to 50% each year. Even avoiding one long distance return flight per year could make a difference. Not only that, it sends a signal to politicians and businesses that people around the world want to find alternatives to carbon intensive travel.

When travelling for leisure, instead of flying to far away destinations, we can consider staying “local”, or see if flying could be replaced with a greener mode of transport, especially train, hybrid coach or an EV.

Business travellers could increasingly adopt virtual meeting technology. If frequent travel is essential, swapping several short trips with a longer one to the same destination could contribute to limiting one’s carbon footprint.

Participating in monthly pledges such as the one by Count Us In to actively change personal behaviour, can help with accountability and inspire others for the common goal.

We could also actively choose to offset flight emissions or fly with airlines using greener fleets.

Whatever we do, the time is now to contribute to a more sustainable aviation sector.

So what next?

Hopefully you now have an understanding of the problems surrounding aviation and the importance in making it sustainable. However, as you’ve seen, there are also lots of barriers that need to be overcome.

This is where we need you!

We would love for you to join our two upcoming workshops and help us take forward a real project that has the potential to have an impact on the climate crisis.

Join our collaborative community!

And keep up to date with our latest news on Twitter and Instagram and Facebook.

AEF (2018) AEF discussion paper on aviation and climate change.

Amadeo, K (2020) Carbon Tax, Its Purpose, and How It Works.

Amadeo, K (2019) Carbon Emissions Trading.

Air Transport Action Group (2021) Aviation industry reducing its environmental footprint.

European Commission (2021) EU Emissions Trading System (EU ETS).

Feldman, S (2019). How the World Puts a Price on Carbon

ICAO (2019) Feasibility of a long term global aspirational goal for international aviation. 

ICAO (2019) 2019 Environmental Report: DESTINATION GREEN. The Next Chapter.

ICAO (2017) RENEWABLE ENERGY FOR AVIATION (Report)

McKinsey & Co (2020) How airlines can chart a path to zero-carbon flying.

Our World in Data (2020). GHG Emissions by Sector

Project Drawdown (2021) Efficient Aviation.

University of Reading (2020). Aviation contributes 3.5% to the drivers of climate change that stem from humans

World Bank (2020) State & Trends of Carbon Pricing 2020.


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