Airplanes' Impact: Air Pollution And Environmental Concerns

Airplanes are a major contributor to air pollution and global warming. While flying is one of the most carbon-intensive activities, contributing 2.4% to 4% of global carbon emissions, only 10% of the world's population chooses to fly in most years. As incomes rise, this is expected to change, with the number of passengers forecasted to rise from 2.4 billion in 2010 to 8.2 billion in 2035. The aviation industry's emissions have more than doubled since 1990 and are expected to triple by 2050, constituting almost 5% of global emissions. Aircraft engines emit ultrafine particles, soot, nitrogen oxides, and lead, causing an estimated 6,800 to 16,000 premature deaths per year. To combat this, new aircraft models are being designed to be more fuel-efficient, and the use of electric aircraft and carbon-neutral fuels is being explored.

Airplanes emit 100x more CO2 per hour than trains or buses

Air travel is one of the most carbon-intensive activities, contributing about 2% of global carbon emissions. However, this figure is expected to rise as other sectors of the economy become greener. For instance, flying emits around 100 times more CO2 per hour than taking a shared bus or train. To put this into perspective, an economy-class return flight from London to New York emits an estimated 0.67 tonnes of CO2 per passenger, which is equivalent to 11% of the average annual emissions for someone in the UK.

The significant carbon emissions from air travel are largely due to the burning of jet fuel, which produces CO2 as well as non-CO2 emissions. These non-CO2 emissions, such as nitrogen oxides, soot, water vapour, and sulfate aerosols, have an increased warming effect when released at high altitudes. They persist longer and have a stronger warming potential than similar emissions from lower-altitude transport modes. Additionally, the formation of condensation trails (contrails) contributes significantly to aviation-related climate change. Contrails are the result of soot from engine exhaust mixing with cold, humid air, forming clouds of ice that reflect sunlight during the day and trap heat at night.

The aviation industry has recognised the need to address these environmental concerns. Aircraft manufacturers like Boeing, Airbus, and other smaller companies have started meeting and even exceeding CO2 emission requirements. By 2028, all regional and seven out of ten mainline US carriers will meet the emission standards for their fleet averages. Furthermore, the International Council on Clean Transportation (ICCT) reported that carbon dioxide (CO2) emissions from commercial aviation grew at a slower pace than the industry's growth between 1970 and 2019. This was achieved through advances in engine and design technology, improved air traffic operations, denser seat configurations, and higher passenger loads, reducing the energy intensity of air travel by 77% during this period.

Despite these efforts, the demand for air travel continues to rise, and aviation's contribution to global emissions is expected to increase. As incomes rise, more people will be able to afford flying, and technological improvements will be necessary to accommodate this growing demand. To combat this, researchers have proposed a range of solutions, including flying less, improving fuel efficiency, using carbon-neutral fuels, optimising flight paths to avoid contrail formation, and electrifying short-range flights with renewable energy sources.

The aviation sector's emissions could triple by 2050

The aviation industry has set a goal of achieving net-zero carbon emissions by 2050. This is in line with the International Civil Aviation Organization's (ICAO) Long-Term Aspirational Goal (LTAG) of net-zero emissions by 2050. While the goal is ambitious, it is crucial to address the impact of the aviation sector on air pollution and climate change.

Aviation is a highly energy-intensive sector, and the number of people flying has increased significantly over the years. In 2019, passengers travelled over 8 trillion kilometres, quadrupling the demand since 1990. This increase in demand has resulted in a rise in emissions. Between 1990 and 2019, global aviation emissions quadrupled, reaching approximately 1 billion tons of CO2 per year. While aviation contributes only about 2.5% of global CO2 emissions, this share has been increasing and is projected to grow further.

To achieve net-zero emissions, the aviation industry is exploring various strategies. These include the use of sustainable aviation fuels (SAF), carbon offsetting, and the development of low-emission technologies such as electric and hydrogen-powered aircraft. SAF can reduce emissions by up to 80% and is compatible with existing aircraft and infrastructure. However, high production costs and limited supply have hindered its widespread adoption. Carbon offsetting, while controversial, can also play a role in reducing the industry's carbon footprint.

Additionally, improvements in aircraft and engine design, as well as operational optimizations, can enhance fuel efficiency and reduce emissions. For example, new aircraft models from Boeing and Airbus already meet or exceed CO2 emission requirements. Airlines are also improving their overall fleet efficiency by introducing newer, more efficient planes. However, retrofitting old planes with new technologies is often not cost-effective, so new aircraft with built-in emission-reducing technologies will be necessary.

While the aviation sector is taking steps towards net-zero emissions, it is important to recognize that aviation activity has a significant impact on air pollution and contributes to global warming. The most effective way to reduce the climate and health impacts of aviation is to simply fly less. A sustained annual decrease in air traffic, combined with the transition to carbon-neutral fuels and more efficient aircraft, will be crucial in mitigating the environmental and health consequences of aviation.

Aircraft engines emit ultrafine particles, causing 6,800 premature deaths annually

Aircraft engines emit ultrafine particles (UFPs) in and near airports, as well as during takeoff and landing. UFPs are even smaller than 0.1 micrometres (PM0.1) and are generated by combustion-related activities. These particles are not just released into the atmosphere but can also be detected on the ground, with studies finding them in the suburbs of Los Angeles, large areas of west London, and several other European cities. This means that millions of people are exposed to UFPs, and their health is at risk.

UFPs are harmful because they are tiny enough to be inhaled and enter the bloodstream, and have even been found in people's brains. A 2020 study from the University of Illinois found that ultrafine particles cause more pulmonary inflammation and are retained longer in the lungs compared to fine particles. The Dutch Health Council and the World Health Organization (WHO) in 2021 highlighted the growing evidence that UFPs damage our health, with 75 studies showing links to lung inflammation, blood pressure issues, heart problems, and risks to foetal growth.

The Transport and Environment study estimated that people within a five-kilometre radius of an airport breathe air containing 3,000 to 10,000 particles/cm3 emitted by aircraft. This puts people living near airports at higher risk, and it is estimated that aviation-caused air pollution leads to 6,800 premature deaths annually. While new aircraft from Boeing and Airbus meet CO2 emission requirements, and the industry is improving its overall fleet performance, the issue of ultrafine particles from aircraft engines remains a pressing concern.

To address this issue, some suggest cleaning the exhaust as it leaves the airplane engine, similar to a catalytic converter on a car. However, retrofitting old planes is not cost-effective, so new planes would need to be built with these cleaning mechanisms in place. Regulations and incentives may be required to push airlines towards adopting more efficient planes with post-emission controls. While some solutions focus on using flight paths that avoid contrail formation, others suggest using a mix of sustainable fuels or electrifying short-range flights with renewable energy sources.

Air traffic causes aircraft noise, which can disrupt sleep and affect children's school performance

Aircraft noise is one of the most detrimental environmental effects of air traffic. It can cause community annoyance, adversely affect academic performance, and disrupt sleep for people living near airports. Aircraft noise has been linked to a range of negative health consequences, including hearing impairment, hypertension, and increased risk of heart attacks.

The RANCH study, a large-scale cross-sectional study of 2844 children aged 9-10 years from 89 schools around London Heathrow, Amsterdam Schiphol, and Madrid Barajas airports, found exposure-response associations between aircraft noise and poorer reading comprehension and recognition memory. The study took into account social position and road traffic noise and found that any reduction in aircraft noise exposure should lead to improved reading comprehension.

Aircraft engines are the major source of noise, often exceeding 140 decibels (dB) during takeoff. While airborne, the main sources of noise are the engines and the high-speed turbulence over the fuselage. Aircraft noise can also be caused by aerodynamic factors, such as airflow around the surfaces of the aircraft, especially when flying low at high speeds. Additionally, noise can be produced by aircraft systems such as the cockpit, cabin pressurization, conditioning systems, and auxiliary power units.

The impact of aircraft noise on sleep disturbance varies depending on the number and acoustical properties of noise events. While aircraft noise may be less likely to disturb sleep compared to road and rail traffic noise, it can still have an impact, especially with intermittent noise patterns. Overall, air traffic contributes to aircraft noise pollution, which can have detrimental effects on the health and well-being of individuals living near airports, including sleep disruption and decreased school performance.

Electric aircraft operations produce no emissions, but large, long-haul aircraft are unlikely to become electric before 2070

Electric aircraft are considered one of the most promising technologies for significantly reducing the environmental impact of aviation. While electric aircraft operations produce no emissions, the transition to electric aviation is a complex and challenging process that requires overcoming several technological and logistical hurdles.

One of the primary challenges is battery technology. Batteries need to be lightweight and have high energy density to power aircraft over long distances. Currently, batteries capable of powering large, long-haul aircraft do not exist, and it is unlikely that this technology will be available before 2030. The weight of the batteries and the cooling equipment required to prevent overheating are significant barriers.

The UK's Jet Zero strategy aims for net-zero aviation by 2050, and research co-commissioned by the UK government and the Climate Change Committee concluded that all-electric aircraft are unlikely to be in commercial service before this date. However, ongoing improvements in battery technology and energy density are making steady progress, and electric aircraft may become viable for selected long-haul routes with low geophysical complexity in the coming years.

In the meantime, other solutions are being explored to reduce aviation emissions. These include improving fuel efficiency, using a mix of sustainable fuels, employing post-emission controls, and optimizing flight paths to avoid contrail formation. Additionally, electrofuels, or synthetic fuels, produced by combining hydrogen extracted from water through electrolysis with carbon, offer a promising alternative. These fuels can be used with minimal or no modifications to aircraft and have already been used in passenger flights.

While the transition to electric aviation for large, long-haul aircraft is unlikely to happen before 2070, a combination of these short-term solutions can help reduce the climate and health impacts of aviation in the near future.

Frequently asked questions