How Green Is Jet Fuel?

Jet fuel is a fossil fuel that powers aircraft and contributes to air pollution. It emits carbon dioxide, water vapour, volatile organic compounds, nitrogen oxides, soot, and other pollutants. These emissions have adverse health effects on airport personnel and residents in nearby areas, including respiratory issues and an increased risk of cardiovascular disease and cancer. While aviation accounts for about 3.5% to 4% of global warming, the sector has made limited progress in transitioning to low-carbon alternatives. The impact of jet fuel pollution is concerning, and further research is needed to understand the long-term health consequences of exposure.

Jet fuel's impact on climate change

Jet fuel has a significant impact on climate change. Burning jet fuel releases carbon dioxide (CO2), nitrogen oxides (NOx), water vapour, soot, and aerosols, which react with the atmosphere and contribute to global warming. While some of these emissions have a cooling effect, the overall impact is warming. Aviation is responsible for approximately 3.5% of effective radiative forcing, which measures the difference between incoming and outgoing energy, resulting in a warmer atmosphere.

The carbon intensity of jet fuel, or the amount of CO2 emitted per unit of energy, has remained unchanged since 1990. While flying has become more energy-efficient, the carbon efficiency of travelling per kilometre has also increased. The growing global demand for air travel has led to a quadrupling of passenger and freight demand since 1990, resulting in an overall increase in emissions.

Aircraft emissions occur primarily at high altitudes, with 90% of emissions happening above 3,000 feet. These emissions have a significant impact on local air quality, with nitrogen oxides, sulfur oxides, hydrocarbons, and soot particulates affecting both aircraft ground operations and low-altitude flights. Additionally, airport ground service equipment and vehicles contribute to aviation's impact on climate change and air quality.

To address the environmental impact of jet fuel, cooperation between states and organisations is necessary, along with significant changes in government and sectoral policies. Some countries have implemented strategies, such as France's national low-carbon strategy, which promotes the use of alternative jet fuels. However, the aviation industry's transition to low-carbon fuels has been slow, and without a shift to electrification, biofuels, or hydrogen, aviation will continue to contribute a growing share of global emissions.

The chemical composition of jet fuel, particularly the level of aromatics, influences the formation of contrails, which are long cloudy strips that trap heat. Reducing the aromatics in jet fuel and improving engine design can decrease exhaust particulates and contrail formation. Sustainable biofuels blended with kerosene jet fuel have been introduced to the market, offering a lower lifecycle greenhouse gas assessment and reduced soot and water vapour emissions.

Health effects of jet fuel exposure

Jet fuel is a major contributor to global carbon emissions and air pollution. The carbon intensity of jet fuel has not changed since 1990, and biofuels and other alternatives only make up a tiny fraction of global demand. As a result, aviation's share of global emissions is expected to increase as demand grows.

Jet engine emissions contain large amounts of nano-sized particles, which are particularly prone to reach the lower airways upon inhalation. Exposure to jet engine emissions has been associated with biomarkers of exposure and effect among airport personnel, especially those in ground-support functions. Proximity to running jet engines or airports for residential areas is associated with increased exposure and an increased risk of disease, hospital admissions, and self-reported lung symptoms.

Several studies have investigated the health effects of exposure to jet fuel. One study found that airport particles were reported to act as adjuvants in the activation of inflammatory cells or pathways and induce pro-inflammatory cytokines. Airport particles were also shown to have a similar ability to induce DNA damage as traffic emission particles and generate high levels of ROS, which is associated with the risk of cardiovascular disease.

In addition, jet fuel exposure has been linked to nervous system effects, including acute symptoms such as dizziness, headache, nausea, and fatigue, as well as chronic symptoms such as depressed mood, lack of initiative, sleep disturbances, memory impairment, and balance problems. Jet fuel exposure has also been associated with respiratory symptoms, such as decreased lung function, increased lung damage, labored breathing, cough with phlegm, and a stuffy and runny nose. However, the available studies on the health effects of jet fuel exposure are limited, and more research is needed to confidently connect jet fuel exposure to specific health conditions.

Jet fuel's contribution to air pollution

Jet fuel contributes to air pollution in several ways and has adverse health and environmental effects. The combustion of jet fuel, particularly fossil jet fuel, emits various pollutants, including carbon dioxide (CO2), water vapour, volatile organic compounds (VOCs), nitrogen oxides (NOx), soot, and sulfate ions. These emissions contribute to global warming and climate change. Aviation is estimated to account for approximately 3.5% of effective radiative forcing, a measure of the difference between incoming and outgoing energy, resulting in a net warming effect on the atmosphere. The burning of jet fuel also affects the concentration of atmospheric gases and pollutants, leading to short-term increases and long-term decreases in ozone and methane.

Additionally, jet engine emissions have been associated with adverse health impacts. Studies have shown that exposure to jet engine emissions is linked to biomarkers of exposure and effect, particularly among airport personnel and those residing near airports. The health effects include respiratory issues, such as sensory irritation and decreased lung function, as well as potential impacts on the nervous system, mental health, and increased risk of certain cancers.

The specific type of jet fuel and aircraft engine also influence the level of emissions and pollution. Different aircraft types use a range of kerosene-based jet fuels with varying kerosene ratios and additive requirements. Exposure to jet fuel components can occur through inhalation, dermal contact, or ingestion, and the health effects can vary depending on the duration and frequency of exposure.

To mitigate the environmental and health impacts of jet fuel pollution, efforts are being made to transition to more sustainable alternatives. However, the aviation sector has been slow to adopt low-carbon fuels, and biofuels and other alternatives currently represent only a tiny fraction of global demand. While improvements in energy efficiency have partially offset the emissions from increasing demand, the absolute emissions continue to rise with the growing number of flights.

Therefore, addressing jet fuel's contribution to air pollution requires a combination of transitioning to low-carbon and alternative fuels, improving aircraft energy efficiency, and implementing policies that actively reduce aviation emissions. The cooperation between states, organizations, and sectoral policy changes are crucial in combating the worsening climate change effects caused by jet fuel pollution.

Jet fuel alternatives

Jet fuel is a major contributor to global carbon emissions, accounting for 2% of all carbon dioxide (CO2) emissions and 12% of all CO2 emissions from transportation. In addition to CO2, jet fuel also affects the concentration of other atmospheric gases and pollutants, such as ozone, methane, water vapour, soot, sulphur aerosols, and water contrails.

The aviation industry has set an ambitious goal of reaching net-zero carbon emissions by 2050. To achieve this, the industry is exploring various alternatives to conventional jet fuel. One of the most promising options is Sustainable Aviation Fuel (SAF). SAF is made from non-petroleum feedstocks, such as renewable biomass and waste resources, and has the potential to significantly reduce carbon emissions from aviation. SAF can be blended with conventional jet fuel at different levels, with limits between 10% and 50%, depending on the feedstock and production method. It has similar properties to conventional jet fuel, making it compatible with existing aircraft engines and infrastructure. SAF has already been used in over 360,000 commercial flights at 46 different airports, mainly in the United States and Europe.

Another alternative jet fuel that has gained attention is hydrogen (H2). Hydrogen has several advantages over conventional jet fuel, including a higher energy content per weight, no CO2 emissions during combustion, superior cooling properties, and a wider stability range. However, hydrogen is highly flammable and has a short ignition time, which presents safety challenges that need to be carefully addressed.

Electrofuels, produced from electricity via electrolysis of water and captured carbon or nitrogen, are also being explored as potential jet fuel alternatives. Examples of electrofuels include Fischer-Tropsch kerosene, methane, methanol, hydrogen, ammonia, and n-octane. While these fuels show promise, there are still challenges to be overcome in terms of production and infrastructure.

Bio-jet fuels, which are blended with conventional jet fuel at low levels, offer another option for reducing emissions. This approach decreases exhaust toxicity while maintaining energy content and fuel properties similar to those of conventional jet fuel, making it easier to adopt in existing engines.

The aviation industry's transition to alternative fuels is crucial to mitigating the environmental impact of jet fuel pollution. While SAF, hydrogen, electrofuels, and bio-jet fuels show potential, further research, development, and infrastructure improvements are necessary to enable a widespread shift towards more sustainable aviation fuel options.

Jet fuel pollution at airports

The type of aircraft, engine conditions, fuel type, and operation modes all influence the size of particles and emission levels produced by jet engines. Jet fuel, which has remained unchanged since 1990, contains carbon and other pollutants that are released into the atmosphere during combustion. Airports located near residential areas pose a greater risk to human health, as the proximity to running jet engines increases exposure to harmful emissions. Studies have shown that airport personnel and residents living close to airports exhibit increased biomarkers of exposure to jet engine emissions, leading to adverse health effects.

The health effects associated with exposure to jet engine emissions are similar to those caused by exposure to diesel exhaust particles and other traffic emissions. Increased exposure to airport emissions is linked to an elevated risk of disease, increased hospital admissions, and self-reported lung symptoms. In addition to carbon dioxide (CO2) emissions, jet fuel combustion releases nitrogen oxides (NOx), water vapour, soot, sulfur aerosols, and water contrails, contributing to the warming of the atmosphere. These non-CO2 emissions have a more significant impact on global warming than aircraft CO2 emissions, highlighting the urgency of addressing jet fuel pollution.

To combat jet fuel pollution, the aviation industry must transition from jet fuel to more sustainable alternatives, such as electrification, biofuels, or hydrogen. While biofuels and other alternatives currently represent a small fraction of global demand, they hold the key to reducing the sector's carbon footprint. In the short term, reducing corporate travel and choosing more sustainable modes of transportation can help curb aviation emissions. Additionally, the development of zero-emissions aircraft, such as hydrogen or electric planes, shows promise in decreasing aviation emissions for shorter ranges.

Addressing jet fuel pollution at airports requires a multifaceted approach, including technological advancements, policy interventions, and behavioural changes. By transitioning to cleaner fuels, improving energy efficiency, and reducing demand through sustainable travel choices, we can mitigate the environmental and health impacts of jet fuel pollution and contribute to a more sustainable future for aviation.

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