The environmental cost of air travel

Why is flying not considered a sustainable form of mobility?

In environmental terms, carbon emissions, other emissions, and the noise associated with aircraft as well as the necessary land usage are the most relevant arguments brought by critics. Aviation is responsible for around 2–3% of global carbon emissions, with this share growing. In addition to carbon dioxide, other emissions such as nitrous oxide, water vapour, and contrails contribute to global warming.

Noise from aircraft can diminish the quality of life of people living close to airports and can have negative health impacts. And finally, airports occupy large areas of land and can lead to changes in land use and a loss of biodiversity. This problem was made clear in the discussions about the construction of a third runway at Vienna International Airport, for example.

Do we need aviation?

Not all flights seem to be necessary. When examining the specific purpose of and rationale for individual flights, the negative arguments outlined above are exacerbated by the problems of low-cost flights, a high share of short-haul flights, and a rapid increase in non-time-critical air freight operations.

Cheap flights generate significant demand for flight services and lead to a higher number of flights, just as the increase in air freight does, which amplifies the aforementioned environmental issues. While originally being limited to individual product groups with a high value and urgency, a short shelf life, and high temperature sensitivity, air freight is now also used to carry cheap goods, for example from online shops located in China.

In addition to e-commerce, global supply chain management – where companies are increasingly employing just-in-time sourcing models that require the rapid and reliable delivery of components – is a key driver of the growth in air freight.

Comparison of alternative means of transport

Compared with other modes of transport, the emissions per kilometre, the energy efficiency, and the availability of other modes of transport are all arguments against the use of aircraft. Planes emit more CO2 than trains or buses per passenger per kilometre, especially when used over short distances.

Carbon emissions on long-haul flights are roughly 150 to 200 grams per passenger per kilometre, which is around 50% less than for short-haul flights. Modern trains, especially high-speed trains, are often more energy efficient and generally emit well under 100 grams of CO2 per passenger per kilometre, which is considerably less than the emissions per passenger for aircraft.

This means that trains, buses, or car pooling can be more sustainable alternatives for short to medium distances. An average car with an internal combustion engine with only one occupant emits more than 140 grams of CO2 per kilometre. At full occupancy, i.e. with four persons, the emitted CO2 per passenger per kilometre would only be one fourth of that. The carbon emissions of electric cars naturally depend significantly on the source of the electricity.

The question of whether sustainability considerations will really lead to a decrease in air traffic in future is difficult to answer. The projections clearly point in the other direction, with the kilometres flown in civilian aviation possibly even doubling by 2050.

Access to flights is increasing rapidly in Asia now in particular. India is one of the countries with the highest projected growth rates in the next decades.

The factors that may facilitate a more sustainable future for aviation include technological innovations, political measures, and changes in consumer and corporate behaviour.

New technologies

In technological terms, developments in the field of sustainable aviation fuels – SAF –could bring a reduction in negative environmental impacts without reducing the number of flights. SAF are fuels made from renewable sources such as biomass and waste materials via synthetic processes.

Improved energy efficiency is also a major aspect in aircraft development. In addition, the use of electric aircraft or aircraft that are powered by hydrogen could make a positive sustainability contribution. However, battery-powered and hydrogen-powered aircraft will likely only fly over short distances in the early stages of adoption. Technological innovations could increase these distances to a few thousand

Fuel tax

Political measures could be taken to decrease demand for air travel, such as

• the introduction of tighter emissions targets for the aviation industry or

• higher taxes on aviation fuel and tickets.

International agreements contravene the taxation of aviation fuel. The most famous example of this is the Chicago Convention from 1944, which generally prohibits taxes on fuel for international flights in the signatory countries, but exceptions are possible. The introduction of an aviation fuel tax is being discussed at the EU level, but fuel for international flights is currently tax exempt in most EU countries.

International treaties

International agreements such as the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) also aim to limit emissions from aviation. CORSIA is striving to stabilise the carbon emissions from international air travel at 2020 levels, regardless of to what degree air traffic grows. According to these rules, emissions that exceed 2020 levels must be offset by compensation measures or the use of sustainable fuels.

Urban Air Mobility

The topic of urban air mobility will become significantly more important in the coming years and will become a reality in the world of modern aviation. This is a mobility concept that uses the airspace above urban areas to provide transport services for people and goods. This pertains to airport shuttles, city air taxis, and short regional hops of up to 250 kilometres between major cities, all the way to autonomous flying drones. “Peaceful” drones could especially be used for modern delivery and parcel services, especially for time-critical dispatches or in areas that are difficult to access with ground vehicles.