By Yemi Olakitan
The aviation sector is one of the most challenging industries to decarbonize, as it requires high-energy-density fuels and has long innovation cycles. However, the sector has committed to achieving net-zero emissions by 2050 and identified several actions to reach that goal. According to reports, some of the main actions included the Improvement of fuel efficiency of existing and new aircraft, through technological innovations and operational improvements.
Scaling up the production and use of sustainable aviation fuels (SAFs), which are drop-in fuels derived from renewable or waste-based feedstocks that reduce carbon dioxide emissions compared to conventional jet fuel.
Developing and deploying new types of aircraft that use alternative energy sources, such as battery-electric, hybrid-electric, and hydrogen-powered aircraft and Compensating for the residual emissions that cannot be eliminated, through carbon offsetting or removal schemes.
The aviation sector faces many challenges and uncertainties in implementing these actions, such as the availability and cost of renewable energy, the technical feasibility and safety of new aircraft, the regulatory and policy frameworks, and consumer demand and acceptance. Therefore, the sector needs to collaborate and coordinate across the value chain, and with other stakeholders, to accelerate the transition to net-zero aviation.
According to industry body the International Air Transport Association, greenhouse gas emissions are rising globally. This has promoted, the European Parliament to announce a proposal to introduce environmental labels for air travel from 2025. The system would serve to inform passengers about the climate footprint of their flights.
Carbon dioxide accounts for only about a third of the global warming effect attributed to air travel. Two-thirds are caused by other factors, most significantly the condensation trails, or contrails, aircraft leave behind.
Contrails — those narrow, white clouds that trace an aeroplane’s path through the sky — are formed when jet fuel, which contains kerosene, burns. At the average cruising altitude of between 8,000 to 12,000 meters (around 26,000 to 40,000 feet), low temperatures cause water vapour to condense around the soot and sulfur left behind by jet emissions. The resulting ice crystals can remain suspended in the air for hours.
Contrails trap heat in the atmosphere, much like in a greenhouse, greatly amplifying the impact of flying on the world’s climate. Recent studies have shown that contrails are around 1.7 times more damaging than CO2 emissions when it comes to global warming.
Several contrails drift against a blue and orange sky.
Contrails, which can linger for hours, trap heat in the atmosphere
On the plus side, contrails are relatively easy to avoid. Using satellite data, flight planners can optimize aircraft routes to avoid weather patterns that favour the formation of contrails. Pilots can also fly their jets 500 to 1,000 meters lower, for example, where temperatures aren’t as cold.
The European Union aims to include these non-CO2 climate effects in future European emissions trading agreements. Airlines will have to start reporting such pollutants from 2025, according to a preliminary agreement in the European Parliament.
Burning kerosene derived from petroleum produces lots of CO2 and, at high altitudes, other greenhouse gases such as ozone. The CO2-free alternative is e-kerosene.
E-kerosene can be produced in a climate-neutral way using green electricity, water and CO2 extracted from the air. First, hydrogen is generated using a process involving electrolysis, and then CO2 is added to produce synthetic e-kerosene.
The problem is that to be cost-effective, e-kerosene needs to be made with plenty of solar and wind power — and so far, there isn’t enough of this renewable energy. New production plants for green hydrogen, CO2 direct air capture and synthetic fuels must also be built.
Another option for planes is to refuel with biokerosene, which can be made from rapeseed, jatropha seeds or old cooking oil. Small-scale production plants already exist, but producers would need to greatly expand capacity to keep up with demand.
Intensive production of biokerosene is also limited by the scarcity of arable land — the use of which is itself controversial, as it prevents take space needed for growing food.
Under a European Commission proposal, biofuels and e-kerosene would be mixed with conventional fossil kerosene from 2025. The share of biofuels in the mix would then rise by 2% per year, to reach 70% by 2050. The proposal is yet to be passed.
Battery-powered short-haul flights on the horizon
With electric engines and batteries, flights could avoid producing direct emissions or heat-trapping contrails. But current batteries are too heavy and have insufficient storage capacity, limiting planes to short distances of just a few hundred kilometres.
A private jet sits on a runway private jet sits on a runway.
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This all-electric jet from Eviation Aircraft is expected to have a range of 445 kilometres
Image: Aviation Aircraft
Several companies are in the process of tinkering with battery and aircraft optimization. Israeli manufacturer Eviation Aircraft, for example, is building an all-electric jet with seating for nine passengers. The private aircraft is expected to have a range of 445 kilometres and a top speed of 400 kilometres per hour (about 250 miles per hour).
Norway is aiming to launch the first regularly scheduled electric flight service in less than three years. The country plans to connect the coastal cities of Bergen and Stavanger, some 160 kilometres apart, with a flight served by a battery-powered aircraft with space for 12 passengers from 2026.
Smaller aeroplanes that run on hydrogen have recently been in the spotlight. These aircraft use hydrogen fuel cells to generate electricity and efficiently power the plane’s propellers. The jet engines on long-haul aircraft can also run on hydrogen but would be less efficient.
European aircraft manufacturer Airbus is planning to launch a hydrogen-powered passenger plane by 2035. These aircraft could account for more than 30% of global air traffic by 2050, according to a study by global consulting firm McKinsey.
However hydrogen-powered aircraft continue to pose numerous challenges. The volatile gas only becomes liquid at minus 253 degrees Celsius (minus 423 Fahrenheit) and must be stored under high pressure in special tanks. That means extra space and weight requirements for aeroplanes, and those plans have yet to be developed. In addition, airports will need to develop new refuelling infrastructure for hydrogen-powered aircraft.
Hydrogen — the fuel of the future?
Even in the most optimistic scenarios, air travel won’t be completely free of emissions by 2050. Experts believe that if the industry implements ambitious restructuring plans — completely replacing standard jet fuel with green hydrogen and e-kerosene, and rerouting planes to prevent contrails — it could reduce greenhouse gas emissions by up to 90%.
However, a recent study in the scientific journal Nature noted that even a complete switch to e-kerosene would still result in a residual negative effect on the climate.
Therefore, avoiding all but necessary flights and giving preference to climate-friendly modes of transportation remains key, said the UBA, Germany’s federal environment agency.
A screenshot of the Flighttracker website, showing dozens of yellow aeroplanes in the sky above Europe screenshot of the Flighttracker website, showing dozens of yellow aeroplanes in the sky above Europe
Aviation experts have also stressed the need for new, lightweight aeroplanes with optimized wings, the use of propellers instead of jet engines and reduced airspeed. They point out that these measures could reduce fuel use by around 50%, compared to today.
Integrating environmental costs into the price of airline tickets would help to implement all these measures, according to the European Clean Transport campaign group Transport and Environment (T&E). Airlines currently pay nothing to account for their contribution to the climate crisis.
Including environmental costs in airfares would be a fair way to promote a restructuring of the aviation industry and would make it easier to switch to climate-friendly modes of transport, according to T&E.
In Africa, decarbonization of the aviation sector is a complex and urgent issue that requires coordinated action from various stakeholders. Many challenges hinder the transition to low-carbon aviation in Africa.
African airlines face higher costs than their counterparts in other regions, especially for jet fuel, which accounts for about 31.2% of their expenses. This reduces their profitability and limits their ability to invest in cleaner technologies and fuels.
Furthermore, Africa lacks a harmonized and consistent policy framework that incentivizes and supports the adoption of low-carbon solutions in the aviation sector. There is also a need for more collaboration and coordination among African countries and regional organizations to align their climate goals and strategies.
Sustainable aviation fuel (SAF) is a key solution for reducing aviation emissions, but it is currently much more expensive than conventional jet fuel. The production and supply of SAF in Africa are also limited by the availability of feedstocks, infrastructure, and technology.
According to various reports, there is a lack of awareness and trust among passengers, airlines, and regulators about the benefits and safety of low-carbon solutions, such as SAF and new aircraft designs.
There is also a need for more effective communication and education to inform and engage the stakeholders and the public about the challenges and opportunities of decarbonizing aviation in Africa.
To overcome these challenges, Africa needs a multifaceted strategy that includes modernizing technology, deploying low-carbon fuels, promoting energy efficiency and sustainability practices, and educating staff and customers.
