Air Travel

The idea of green air travel at first seems impossible. Though air travel in 2009 accounted for about 2–3 percent of anthropogenic carbon dioxide emissions, some estimates have annual aircraft emissions tripling by 2050, the same time period during which many efforts are scheduled to reduce emissions from all other sources. Air travel not only consumes vast amounts of nonrenewable fossil fuels but is also a major contributor to nitrogen oxide in the troposphere. The cumulative effect is such that the per passenger, per mile effect of air travel is nearly as great as that of each passenger driving the same distance himself and is significantly worse than that of small or hybrid cars, or ground mass transit (whether rail or bus). Aircraft contrails, high-altitude vapor trails formed when atmospheric water vapor condenses around particles of engine exhaust, has a noticeable effect on climate as well—great enough that the three-day grounding of U.S. air traffic after September 11, 2001, had a measurable effect on atmospheric temperatures (1 degree Celsius). Furthermore, a significant amount of air travel is travel that would not otherwise occur—few of the tourists taking three-day vacations to the other side of the country or visiting the other side of the world would make such trips if they were limited to other modes of transport. Much of this polluting transit, in other words, is dispensable in a sense that many other sources of pollution are not.

However, these factors also serve to motivate greener forms of air travel. Fuel efficiency is not only good for the environment, it is good for business, and offering a green passenger flight is a value-added incentive that may attract enough customers to offset the expense of the changes necessary to make that flight more energy-efficient or less environmentally damaging.

Aircraft contrails have such an impact on climate that the three-day grounding of U.S. air traffic after September 11, 2001, had a measurable effect (1 degree Celsius) on atmospheric temperatures

Source: iStockphoto

[Page 10]There are actions consumers can take, regardless of whether an airline offers greener service. Because takeoff and landing are the most fuel-using parts of a flight, and because indirect flights involve more total travel miles, a direct flight, though often more expensive, will consume considerably less fuel. Using an airplane bathroom consumes about as much gasoline as six miles of flight, so avoiding it helps reduce one's effect as well, as does packing less (or, less easy to adjust with short notice, weighing less). As with any activity involving greenhouse gas emissions, there is an option to purchase carbon offsets to balance out one's effect.

However, the real potential lies in “greening” air travel itself, at the airline and manufacturer level rather than through passengers' activities. In April 2008, Boeing tested the first manned plane powered only by fuel cells, using hydrogen, converted through chemical reaction into electricity and water. There is no combustion engine, no carbon emissions, so although water vapor is not a benign substance at high altitudes, the assumption (or hope) is that water vapor emissions would be significantly less harmful than carbon. The test plane was too small for more than two people, but the Wright brothers started with a small craft too. In theory, such planes can someday be built on the same scale as today's commercial passenger planes.

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