Reducing pollution in the skies: passengers ready for trade-offs

Reducing pollution in the skies: passengers ready for trade-offs

In 2050, airplanes will release 188 million tons of CO2 into European skies. Are we willing to change the way we fly to pollute less? A survey conducted by the European project ClimOp, coordinated by Deep Blue, suggests that we are.


Flying is becoming increasingly polluting due to the growth in air traffic. From 2005 to 2019, the number of flights in the EU27+EFTA airports increased by 15%, reaching 9.3 million flights. Concurrently, CO2 emissions rose by 34%, reaching 147 million tons. After a sharp decline due to the pandemic (with the number of flights dropping to 4.12 and 5.07 million in 2020 and 2021, respectively), estimates project that by 2050, there will be 12.2 million annual flights, resulting in 188 million tons of CO2 emissions (data from the 2022 European Union Aviation Safety Agency – EASA Environmental Report on European Aviation).




In the medium and long term: fuels and technology

If Europe aims to achieve climate neutrality (zero emissions) by 2050, aviation, which was responsible for 2% of global CO2 emissions in 2021, must play its part. Sustainable Aviation Fuels (SAF) will play a fundamental role in decarbonizing the sector, especially because they can be used immediately without any need to change supply infrastructure and aircraft engines. The European Commission has promoted increasing the blending quota of SAF in fuel supplied to EU airports from 2% in 2025 to 63% in 2050. Technological solutions are also being explored, such as more fuel-efficient engines that reduce particulate emissions and nitrogen oxides (which have a higher climate-altering potential than CO2), aircraft with even more aerodynamic structures, and airplanes with electric or hydrogen engines. Research and development are moving in this direction, but these innovations won’t be available in the short term.


Immediate changes: operational measures

What can be done immediately is to change the way we are used to fly. This is being investigated by the European project ClimOp (Climate assessment of innovative mitigation strategies towards Operational improvements in aviation), coordinated by Deep Blue and funded under the Horizon 2020 program. Its goal is to identify aspects of flight-related activities, airport operations, air traffic control, and management that can be modified to reduce aviation’s polluting emissions. Reducing the environmental impact of operational measures will help achieve one of the European Union’s Flightpath 2050 goals: reducing CO2 emissions by 75% and nitrogen oxide emissions by 90% by 2050.

ClimOp has examined the feasibility and environmental impact of two operational measures: Climate-optimized Intermediate Stop Operations (optimized climate stopover operations) and flying low and slow. Alessandra Tedeschi, Head of Research & Development at Deep Blue and project coordinator, explains: “An airplane consumes, and thus pollutes more when it is heavier. That’s why for long-haul flights, it’s not cost-effective to have planes take off fully loaded with fuel, as they are heavier. Instead, it’s more efficient to have intermediate stops for refueling.” Regarding the other operational measure, she adds: “Planes fly at high altitudes because the air is less dense, which reduces friction and fuel consumption. But at lower altitudes, some polluting emissions have a smaller climate impact. Slowing down also helps. With these interventions, there is a potential climate mitigation of 6.3% for long-haul flights and 12.5% for inter-European flights.”



Technically these are easily implementable solutions, but what about their social acceptance? ClimOp researchers conducted a survey of over 400 passengers aged 18 to 44, asking about their travel habits, awareness of the climate crisis, knowledge of aviation’s environmental impact and, most importantly, their willingness to accept changes in flying habits to make air travel more environmentally friendly.

Among the respondents, awareness of the climate crisis is high (22.2% of the sample) or very high (52.1% of the sample), although only 19.5% are aware of aviation’s current impact on the climate. One striking finding is that whether it’s national, European, or specific aviation-related initiatives, over half of those surveyed are unaware of mitigation actions being taken. Tedeschi says, “We need to focus more on communication: we need more and more effective awareness and information campaigns on the topic.”

Nevertheless, a considerable number of the surveyed passengers understand the value of opting for greener air travel and to do their part. For example, two-thirds of the participants are in favor of boarding longer short-haul and long-haul flights by 20% (30 minutes on a 2.5-hour flight) and 16% (2 hours on an 11.2-hour flight), respectively, compared to current flight times. Tedeschi highlights, “Stopover flights would not only help fight global warming and pollution but also benefit the economy if stopovers are used to promote tourism in the cities where they occur. It’s clear that this is a process that will involve various stakeholders, including airport operators, accommodations, municipalities, tourist attractions, and cultural sites.”


The surveyed passengers would also be willing to pay 25% more (31.8% of the sample) and 50% more (30.1% of the sample) for both short-haul and long-haul flights if it helps reduce emissions from their flights (the operational measures analyzed by ClimOp entail increased costs for stakeholders). Additionally, most passengers would accept less frequent flights with larger and fully occupied aircraft but would have difficulty accepting baggage limitations. Finally, over half of the interviewed are willing to sign a petition to increase low-carbon flights and inclined to choose flights based on their “climate reputation.” Tedeschi concludes, “Passengers are more ‘aware’ than we imagined and willing to make some sacrifices understanding their importance for the environment and climate. The survey data, which have also surprised us as professionals, send a message to all aviation stakeholders: we need to rethink services and business models from a green perspective.”



Aviation pollutes not only because of airplanes. ClimOp has assessed the overall impact of an airport in terms of pollution and contribution to global warming by measuring emissions generated by ground operational vehicles (buses, baggage carts, staff cars, etc.), airport infrastructure (especially buildings and offices), and aircraft taxiing from the landing strip to the gate and back. It was discovered that without significantly changing passengers’ flying habits, the environmental impact of aviation can also be reduced by intervening in ground operations. Carlo Abate, Head of Environment & Energy at Deep Blue, who oversaw the analysis of ground vehicle emissions for ClimOp, explains: “In particular, emissions from heating, lighting, and air conditioning of buildings can be reduced by 20% through energy efficiency.”


CO2, nitrogen oxide, and particulate emissions from aircraft taxiing could decrease by 50% if airplanes were towed by electric tractors. “Similarly, if all ground vehicles were powered by electric motors and electricity came from renewable sources, emissions could be virtually eliminated,” Abate adds. Reducing polluting emissions at airports, the researcher explains, would have a dual benefit: on one hand, the impact of a medium-size

On one hand, the impact of a medium-sized airport (approximately 300 flights per day) would be roughly halved in terms of its contribution to global warming. On the other hand, the reduction of polluting gas emissions and particulates would contribute to improving ground-level air quality, benefiting workers, passengers, and local communities (in the case of urban airports).


Read the ClimOP Project Survey

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