Air travel

Air travel

When the Wright Brothers took flight at Kitty Hawk in 1903, they were probably more concerned with staying aloft and alive than they were with their airplane’s CO2 emissions. But today the air travel industry has multiple environmental concerns, including significant greenhouse gas emissions, contrails, excessive airport waste, and water pollution from de-icing operations.

These concerns are likely to intensify along with the industry’s growth. In 2004, more than 600 million US passengers boarded an airplane to attend business meetings or vacation destinations. By 2010, that number is expected to grow to more than 1 billion.[1] And that’s just in the US. Europe, Asia, and especially China are all forecasting explosive growth in air travel as well.

Impact from air travel

Climate change

Currently, air travel accounts for 7 percent of worldwide carbon emissions and 2.7 percent of total US emissions.[2][3] Part of the problem is that the majority of an aircraft's emissions occur at high altitudes. The Intergovernmental Panel on Climate Change (IPCC) notes that greenhouse gas pollution from flying aircraft may be up to four times more damaging to the environment than the same levels of pollution emitted at ground level.[4] Why? The emissions from a jet engine contain about 70 percent CO2, almost 30 percent water vapor, and less than 1 percent each of nitrogen oxides, carbon monoxide, oxides of sulfur, volatile organic compounds (VOCs), particulates, and other trace compounds. Most of these emissions (90 percent) occur at high altitudes where the molecules have more time to trap heat, creating a greenhouse effect.[5]

Emissions of nitrogen oxides in the upper troposphere and lower stratosphere mixing with ozone, methane, and other greenhouse gases also present an environmental threat. Most notably, nitrogen oxides can lead to decreases in the ozone layer, which is the layer that protects the earth from the sun’s ultraviolet radiation.

Additionally, the water vapor emitted while a plane is in the air can turn to ice clouds and produce contrails. Although more research is needed to establish the specific climate impact of contrails, persistent contrails often increase cirrus cloud cover, forming an insulating blanket of moisture and gases in the atmosphere.

Trash

Air travel is responsible for three distinct waste streams: public terminal areas, retail and restaurant tenant located at airports, and waste generated by the actual airlines. According to a report by the Natural Resources Defense Council (NRDC), the airline industry discards enough aluminum cans each year to build 58 Boeing 747s. In addition, airports generate 9,000 tons of plastic and enough newspapers to fill a football field to a depth of 230 feet.[6] Few airports have recycling programs (only about 20 percent). Yet, if the industry recycled 70 percent of the 425,000 tons of waste they generate per year, the energy saved would be equal to that consumed by 20,000 households in a year. Additionally, the amount of reduced greenhouse gas emissions would be equal to removing 80,000 passenger cars from the road each year.[7]

Water pollution

Toxic chemicals—primarily glycols—used to de-ice planes during winter storms can find their way into local waterways if airports don’t have efficient recapture systems. From 1989 to 1991, more than 4 million gallons of glycols were used for aircraft de-icing at just 93 airports.[8] The NRDC notes that glycol can be toxic to fish, wildlife, and humans.

Industry improvements

Fuel Efficiency

With fuel prices escalating, airlines are looking for ways to cut consumption. These incremental changes have reduced the amount of fuel burned by 23 percent since 2000:[9]

  • More efficient routing, altitudes, and speeds to cut fuel use and emissions.
  • Eliminating excess weight on board, including charging passengers a fee for extra checked bags.
  • Investing in lighter, more fuel-efficient planes.
  • Adding winglets to aircraft to reduce fuel burn and emissions.
  • Using electric vehicles for ground-crew operations
  • Cutting the operating time for auxiliary power units on airplanes.
  • Replacing older planes with newer, more fuel-efficient models.
  • Flying at slightly slower speeds cuts fuel consumption and adds just a few minutes to each flight.

The industry is also looking at improved fuel economy. Thirty years ago, airplane engines got a mere 15 miles per gallon (mpg). Today, largely due to engineering advancements in the design of airplanes and the use of lighter materials, airplanes get 50 to 63 mpg.[10] However, improvements in an airline’s overall fuel economy are slow, as aircraft typically remain in the fleet for 35 to 40 years.[11]

Alternative fuels

The airline industry is also investigating the potential use of alternative fuels. In 2008, Virgin Atlantic put this investigation into action by flying a Boeing 747 powered partially with biofuel from London to Amsterdam. Aside from biofuel, other alternative fuels being considered for future use are Fischer-Tropsch synfuels and ethanol. Fuels made from liquefied coal, oil shale, and tar sands—all fossil fuels opposed by the NRDC because they come from polluting sources—are also being carefully evaluated.[12]

Carbon offsets

Until a more sustainable solution to curbing greenhouse gases in air travel is found, many airlines are offering passengers the option to purchase carbon offsets with their tickets. Delta Air Line's program, for example, offers to plant trees via The Conservation Fund in return for $5.50 for a domestic round-trip ticket or $11 for an international round-trip flight.[13]

Glossary

  • contrails: Line-shaped clouds or condensation trails produced by aircraft engine exhaust. These clouds would not have formed in the sky without the passage of an aircraft.
  • greenhouse effect: A naturally occurring process that warms the earth's atmosphere and surface. This rise in temperature is a result of atmospheric gases trapping energy from the sun.
  • volatile organic compounds (VOCs): Organic solvents that easily evaporate into the air. VOCs are emitted by thousands of products, including paints, cleaning supplies, pesticides, building materials, and furnishings, and may cause immediate and long-term health problems.

External links

Comments

08/18/2008
12:27pm
greengoddess

another easy way to cut back on your plastic cup usage on the flight is to simply bring a large bottle with you and ask the flight attendant to fill it up for you. you not only eliminate the need to waste unnecessary plastic cups but you'll have water at your side whenever you want it.

10/07/2008
12:30pm
enviro.aero

There are some figures on this page that need correcting. Air travel accounts for 2% of world CO2 emissions (UN IPCC figures). The IPCC has an updated study on radiative forcing (the multiplier effect of gasses other than CO2) and the latest research shows a multiplier of 1.9x CO2 effect alone. But it is important to remember that every human activity has a multiplier effect (road transport, power generation etc) and the normal background rate is 1.5x CO2 effect alone. The best way to incorporate all these numbers is to give a 'total climate impact'. The IPCC says is aviation accounts for 3% of total man-made climate impact.

Obviously, any figure is still too much and what this page does do is highlight just a few of the ways in which the aviation industry is working to reduce its climate impact even further. We are now producing aircraft (such as the A380 and Boeing 787) that have the same per-passenger per-kilometre fuel use as hybrid cars and with the advent of biofuels and the advances in technology being made, the industry will continue to strive for even greater efficiency. The air transport industry has established the website www.enviro.aero to open up the debate about aviation's climate change impact and profile just some of the ways in which the industry is making progress.

Haldane Dodd
Air Transport Action Group, Geneva

10/07/2008
3:09pm
Mateo

Haldane, thanks for that valuable contribution. it does look like the 7% figure is dated. the most credible figure i can find is 3.3% (contribution of aviation sector to global warming) published by WRI and IPCC. check out the link here:

http://www.wri.org/chart/us-greenhouse-gas-emissions-flow-chart

also, great to know that enviro.aero is engaging the public to discuss all the issues surrounding the industry and the solutions ahead!

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