Trail air traffic leaves behind...

Last Updated 25 October 2010, 11:58 IST

Ever realised that air travel messes up the environment? True, aviation pollution amounts to only three percent of the total environmental pollution today. Yet, with an air-travel boom expected in the near future, this figure is bound to bloat! Moreover, carbon dioxide (CO2) released at high altitudes is more damaging than at ground-level.
Air traffic emits carbon dioxide, nitrogen oxide, water vapour, unburnt hydrocarbons, soot and sulphate particles. Nitrogen oxide encourages the greenhouse effect, photochemical smog formation and the stratospheric ozone layer’s depletion. Contrails formed by water vapour emission increase the cloud cover in the upper troposphere, resulting in a net warming effect.

Although the adverse environmental impact is lower than from other industries, aviation pollution certainly contributes to global warming. A single trans-Atlantic flight consumes 60,000 litres of fuel (estimated to last 50 years for the average motorist!), releasing 140 tonnes of CO2 into the atmosphere.

Besides, noise from planes affects people’s sleep and work-efficiency, proliferating ill-health and road-accidents. Increased air-travel unleashes greater road-congestion in airports’ vicinity and the countryside’s ravaging with airport-expansion.

Possibility of alternative fuels

What are the measures to alleviate this problem? Major aircraft companies are researching the possibility of using alternative fuels to power airplanes extensively a couple of decades later. Hydrogen is one. But, the current aircraft engines/structures need modifications before it can be employed. Plus, the quantity of hydrogen being produced through renewable energy sources is limited.

Anyway, hydrogen can be burnt in a jet/internal-combustion engine. Hydrogen fuel-cells and cryogenic liquid hydrogen can generate electricity to power a propeller. But, liquid hydrogen’s high volume and volatile nature necessitates storage in fuselage instead of wings. Some prominent airliners have airplanes which utilise hydrogen.

However, a prominent airliner is sceptical about fuel-cells’ ability to power large, commercial planes. At present, they can be used for flying smaller planes and unmanned aircraft and in auxiliary power units for large, commercial airplanes.

Boeing, Altatus, Fishman and Sonex are some of those toying with the idea of electric motor-powered Light Sports Aircraft (LSA). Electra, a single-seater aircraft powered by lithium polymer batteries, completed a 48-minute flight in 2007 in France covering over 50 kms. Fishman’s Electra Flyer-X has two hours’ capability of staying airborne on lithium-ion polymer batteries chargeable from home wall-outlets.

Solar-powered flights

Solar-powered unmanned and manned flights (Solar Riser, Solar Challenger, Sunseeker, Soaring....) are also being experimented with. The Solar Impulse flies on power from solar-cells stored in lithium polymer batteries.

Airline companies have also demonstrated that jet engines can run satisfactorily on fuels derived from live plants/other organic matter. Algae-derived biofuel, 50/50 blend of Jet-A and Camelina-based fuel, babassu and coconut oil combo and ethanol (alcohol-based fuel obtained from sugar and corn fermentation) are success stories.

The jatropha plant’s fuel-source potential is being explored. Recycled cooking oil has flown an aircraft at 17,000 ft. and -4°C. But, it coagulates at -10°C! ‘Gas-to-Liquid’ (GTL) fuel, prepared from natural gas/organic plant products is another contender with lower emissions and greater fuel-efficiency.

Yet, questions surround large-scale biofuel usage. Practising crop monoculture in huge areas for meeting the aviation industry’s enormous biofuel demand leads to deforestation, food-crops’ displacement, food-price escalation and soil-degradation!
Synthetic jet-fuel’s (synfuel) lower energy-density implies carrying of more fuel despite fewer noxious emissions than kerosene.

Prominent airliners are tinkering with aircraft-design. The EcoJet is a proposed short-haul aircraft with propfan engines, for reducing emissions and noise pollution. Kilo-shedding initiatives, flaps setting reduction for landings, winglet  addition and improved engine-wash programmes are some fuel-efficiency boosters.

Passengers too can help. Choose young airlines, opt for carbon-offset schemes, lighten luggage loads, substitute business air-travel with videoconferencing and, in general, travel less by air!

(Published 25 October 2010, 10:49 IST)

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