Q I’ve tried to cut down on airline travel but have to do some journeys for my work. I’ve often wondered about the environmental impact of airlines meals — are the unused ones thrown away?

A Unless you’re lucky or rich enough to be at the front of the plane, airline meals are invariably disappointing. “Tips of asparagus drizzled with extra virgin olive oil served on a bed of crab” — that’s the greenish looking morsel you just downed in one gulp. “Tender beef stroganoff accompanied with a symphony of fresh vegetables.” Ah, that must be the congealed brown and white mixture lurking under the foil.

Arguments over the airline industry's impact on the environment have centred on CO2 emissions and the expansion of airports. Little attention has been given to problems associated with disposing of the considerable amounts of waste produced by air travel. Every time a fully-laden 747 takes off it is laden not just with passengers, luggage and fuel but with 40,000 in-flight items, ranging from drink miniatures to toothpicks.

A stroll through an aircraft filled with the detritus of a 12-hour journey shows the scale of the problem. One study calculated that the US airline industry throws away enough aluminium cans each year to build 58 jumbo jets: meanwhile the annual amount of newspapers and magazines thrown away by airlines travelling the US would fill a football pitch to a depth of 240 feet.

The millions of meals served in the sky each day present their own set of difficulties. The logistics of getting all that food on the aircraft, let alone heating and serving it, is one thing. Disposing of the many tonnes of food plus the plastic trays, cups and plastic bottles, is another.

Air traffic volumes have expanded rapidly over the past 20 years but airport infrastructure has struggled to keep up. While some airports turn food waste into energy, many lack adequate waste disposal facilities, particularly those in the developing world. Also, health and safety regulations in many countries stipulate that all leftover food, used or unused, has to be destroyed.

Not surprisingly, low-cost, no-frills airlines that make you pay for food tend to produce less waste than the more established carriers. Passengers are a fickle bunch: when long-haul carriers attempted to introduce a paid meals policy, even the greener travellers insisted on their in-flight food.

Bringing your own grub is an option, though at some airports a baguette might be confiscated as a security risk. Other than staying at home or travelling by train or car perhaps the only solution is to eat on the ground, not in the clouds.

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