Fuel Dumping: What Is It and How Bad is it for the Environment?

Sometimes, the wispy white trails that follow an aircraft on its flight aren’t contrails but fuel that has been dumped by aircraft. This is also known as fuel jettison. Fuel dumping is a last-resort maneuver whereby a plane releases fuel in mid-air. This may seem environmentally unfriendly, but it is a critical safety measure in aviation. Like fuel tankering and other environmental problems associated with aviation, fuel dumping is worth looking at closely. 

Why a plane dumps fuel mid-flight comes down to weight considerations. Much in the way that airplanes have a maximum takeoff weight, they also have a maximum safe landing weight. If an emergency arises, like an engine malfunction or a medical situation on board, and the plane needs to land unexpectedly. However, the plane might still have too much fuel. As airplane fuel can be as heavy as 6 pounds per gallon, it becomes pertinent for aircraft to shed off the fuel to allow for safe landings. 

However, fuel dumping isn’t without consequences. The jettisoned fuel doesn’t simply disappear. At high altitudes, some of it may combust, contributing to air pollution. At lower altitudes, the unburnt kerosene can disperse and potentially contaminate water sources, soil, and ecosystems. Let’s explore the environmental consequences of fuel dumping in this article. 

Shedding weight in an emergency: Why fuel dumping takes place? 

Take the case of the Airbus A380, for example. This largest passenger airplane ever made, can hold around 82,000 gallons of fuel – each of its ten tanks can, individually, accommodate 8,200 gallons of fuel.

A380 has a maximum takeoff weight of 560,000 kg (1,234,600 lbs) and a maximum landing weight of 386,000 kg (850,984 lbs). If the aircraft experiences an engine failure or a medical situation on board, the excess weight of the aircraft would render it unsafe to land without jettisioning fuel. If the emergency to land the aircraft doesn’t allow extra time to dump fuel, landing the plane can put immense stress on the aircraft’s landing gear and brakes. 

A lighter aircraft, on the other hand, which is comparatively easier to manoeuvre and control in tense situations might not encounter the same problem, though.

How does fuel dumping take place? 

Flight crew has access to the aircraft manufacturer’s guidance on the fuel dump system. If the aircraft is devoid of dump system making the aircraft heavier than the maximum landing weight, the pilots should take the following into account:

• minimum runway requirements
• maximum touchdown rate of descent
• use of stopping devices

Crew generally heed the advice of air traffic controllers (ATC), who generally instruct where and at what height dumping is safe to carry out. Dumping fuel at an altitude of around 5,000 ft (six times lower than the height of Mount Everest) to 6000 ft AGL makes sure that the fuel evaporates/ dissipation before reaching the ground.

Manufacturers often don’t have regulations regarding fuel dumping for exceptional cases, such as in-flight fire, claims Skybrary: “in the event of an uncontrollable fire, crews are advised not to delay landing and subsequent evacuation in order to reduce the landing weight by dumping fuel“. The fuel dumping system of an aircraft can dump more than a thousand pounds of fuel per second.

The fuel dumping system of an aircraft comprises of pumps and valves that divert fuel to the tip of the wing’s planes. The system can be activated from the cockpit (by the pilot). After activation, the fuel is dumped from the wingtips, often appearing as a contrail. To ensure that not all fuel in the aircraft is jettisioned all at once, the pilot also has failsafe system. Pilots are privy to how much fuel has been dumped and how much remains.

It is only the bigger planes that dump fuel

Not all commercial aircraft can jettison fuel. Widebody jetliners such as the Boeing 787, Boeing 777, the Airbus A350 (which is deployed on the longest non-stop flight around the world), etc., can jettison fuel. Flight Radar 24 reported that the Boeing 757 didn’t need a jettisioning system because the aircraft’s MTOW and landing weight were fairly similar. The same publication also reported that smaller planes (and sometimes even larger ones) might not even need this system.

Much in the same lieu, it has been said that aircraft such as the Boeing 737 “don’t need to dump fuel when they can simply burn it off within a few orbits of the airport. If the plane needs to land urgently, the fuel onboard won’t significantly hinder the landing operations“.

Military planes also jettison fuel

We might think that it is only the commercial airliners that are involved in fuel dumping, but that is not necessarily the case. Fighter jets such as the Su-30MKI and Mirage 2000 are also equipped with jettison systems. Wion reported that F-111 Aardvark had performed ‘dump and burn’ displays. The aircraft had done so by igniting the wake of fuel it dumped. A Russian Su-27 also had jettisoned fuel onto a US MQ-9 Reaper drone for tactical purposes. In the latter years of the 70s, almost 1000 military fuel dumpings were performed in the US.

The Murky Reality of Fuel Dumping: Unreported Events 

The FAA reported less than thirty fuel dumps each year for all years between 2015 and 2020. The rate of fuel dumping was extraordinarily low-  0.00000588% of flights per year [ US experienced an average of more than 25.5 million flights in its airspace per year, with yearly average flight dumping reported being 15].

FAA did mention that it could account “only account for reported fuel dumping incidents, reported figures do not account for possible outlier instances of flights that dumped fuel during a non-emergency situation; for example, if a pilot erroneously thought the aircraft was overweight, and was on approach to the destination airport“.

Understanding the environmental impacts of fuel dumping

In 2020, a Boeing 777 operated by Delta Air Lines flying from Los Angeles International Airport (LAX) to Shanghai Pudong International Airport (PVG) was forced to return to LAX shortly after takeoff. The engine problem encountered during the flight forced the crew to dump fuel when the aircraft was at an altitude of merely 2,000 ft.

The aircraft dumped almost 15,000 gallons of fuel, a portion of which found its way over the bodies of kids in an elementary school. A former Boeing 777 captain, in addition ot expressing his surprise that dumping took place at such a low altitude, also opined that almost 20,000 gallons of fuel might have been jettisoned. 

Different states in the US have different laws regarding the penalties of dumping waste, though these are not quite specific with regards to whether they exclusively refer to fuel dumped from planes: wastes dumped into public properties (into sewers, waterways) or one’s land without being licensed to do so.

Helen Krasner, a pilot with 15 years of experience flying fixed-wing aircraft, says that there are negligible environmental impacts of fuel dumping. If the volatile aircraft fuel is dumped at a considerable height (over 5,000 ft), fuel doesn’t reach the ground and there are virtually n impacts of land pollution as a result. This is because jet fuel contains different hydrocarbons, including benzene – an exposure to which would decay plants and contaminate groundwater. 

However, things aren’t as simple.

At high atitudes, the jet fuel is crystallized

Most aircraft cruise at an altitude of over 35,000 ft, almost above the clouds, though this is not the case for helicopters. The highest landing of a helicopter has been at the top of Mount Everest, an altitude of around 29,000 ft. Ordinarily, at such an altitude the temperature is below -50°C. Jet-A fuel, which powers most US aircraft, has a cloud point of -47 °C (or -52.6°F), meaning that fuel dumped at such altitudes crystallizes into solids and becomes “a mixture of the two states diffused into a cloud of vapor“. As this drops towards the Earth, temperature increases, and jet fuel evaporates.

Water vapor released by aircraft has relatively little direct warming effect because it has a short atmospheric lifetime. However, it can contribute indirectly to warming by helping form contrails under sufficiently cold and humid conditions. Ice crystals form around particles in the aircraft exhaust, and these can grow by drawing additional water vapor from the surrounding atmosphere. The resulting contrails can persist and spread into larger cirrus clouds that trap infrared radiation and produce a warming effect.

This effect is not simply a consequence of water vapor being released by jet fuel combustion. Contrail formation depends on a combination of aircraft emissions and atmospheric conditions, including temperature, humidity and the presence of particles that act as nuclei for ice crystals. The IPCC likewise identifies persistent contrails as an important non-CO2 climate effect of aviation, with aircraft soot and water vapor contributing to their formation in cold, ice-supersaturated air.

Consequently, the climate impact of contrails needs to be considered as part of aviation’s overall environmental footprint rather than as a direct effect of water vapor alone. Research has found that non-CO2 effects, including contrail-induced cloudiness and nitrogen oxide emissions, make a substantial contribution to aviation’s total climate impact.

The harmful gases released during dump and burn

Sometimes the jet fuel undergo a dump and burn process (whereby fuel is intentionally ignited using the plane’s afterburner). In regular flights, fuel is burnt slowly over time, but in the case of dump and burn, it burns in short powerful intervals (or at one go). Here are some figures that highlight the scale of pollution from commercial avaition:

• 707 million tons of CO2 emissions in 2013 [according to the International Council on Clean Transportation (ICCT)]. In 2019, this figure reached 920 million tons.
• The US accounted for 200 million tons (23 percent) of CO2 in 2017, with EPA reporting “that commercial airplanes and large business jets contribute 10 percent of U.S. transportation emissions, and account for three percent of the nation’s total greenhouse gas (GHG) production”. 
• Global aviation accounted for 2.4 percent of total CO2 emissions in 2018.
• In 2018, 81 percent of global commercial aviation emissions were down to passenger flights while the remaining was due to freight transport.

The exhausts, elucidated in the table below, are associated with respiratory problems and might have different reactions on the body:

Nitrous oxides	causes acid rain.
Carbon monoxide	Affects those with heart disease
Sulfur oxides	Can hinder plant growth