Environment - Limiting Emissions

Is carbon-neutral aviation growth achievable? It looks good as a goal to aspire for, but is hard to attain as long as aviation rapidly expands its global footprint.

January 1, 2012, witnessed perhaps the most significant step taken till date in efforts to limit global aviation emissions. On that day, the European Union (EU) capped aviation greenhouse gas (GHG) emissions in Europe and kick-started an Emissions Trading Scheme (ETS) that applies to all airlines flying to any European destination, irrespective of their country of origin. There have been howls of protest from governments and airlines around the world but for now at least the EU is sticking to its guns. The EU’s go-it-alone measure is intended to spur the adoption of greener technologies and biofuels by the aviation industry.

Flying adversely affects the environment mainly because aero engines emit noxious gases that contribute to global warming which in turn is believed to lead to climate change. Turbofan and turboprop engines have steadily become more fuel-efficient yet rapidly growing air travel worldwide contributes to an increase in total emissions attributable to aviation. In the EU alone, GHG emissions from aviation increased by 87 per cent between 1990 and 2006. Boeing estimates at least 90,000 commercial planes fly daily across the globe spewing a variety of toxic gases, water vapour and particulate matter, carbon dioxide (CO₂) and nitrogen oxide (NOx) being gases of particular concern. The very high operating temperatures of jet engines create small quantities of NOx that have 300 times more powerful GHG effects than CO₂. However, engine designers have largely succeeded in limiting NOx emissions. Hence their focus is on reducing CO₂ or carbon emissions.

Airliners today are 70 per cent more fuel-efficient than the Boeing B707 and Douglas DC-8 of the 1960s and total aviationrelated CO₂ emissions constitute just three per cent of the global GHG emissions. However, as travellers from emerging economies take to the skies in increasing numbers, aviation is today the fastest-growing source of atmospheric pollution. The amount of CO₂ emissions from aviation is expected to grow around three to four per cent annually, much faster than the one to two per cent yearly efficiency gains expected by the industry. Consequently, according to the Inter-governmental Panel on Climate Change (IPCC) aviation-related GHG emissions could rise to between five per cent and 15 per cent of the global total by 2050.

International Efforts

A global system of aviation emissions control would doubtless be much better than a patchwork of competing systems. Back in 1997, the International Civil Aviation Organisation (ICAO), whose membership includes practically every country on earth, was asked to come up with concrete proposals to reduce GHG emissions from air travel. Almost 15 years later, there is little to show for its efforts. However, ICAO now plans to introduce global CO₂ standards for new aircraft types by 2013. The standard is likely to emulate its highly successful “Stage” noise yardsticks. ICAO’s stated goal is to cap civil aircraft emissions at 2020 levels and ensure that further aviation growth remains carbon-neutral. It also aims to achieve a two per cent annual increase in fuel efficiency between 2020 and 2050.

Carbon-neutral growth, which implies keeping the industry’s net CO₂ emissions stable even as demand increases, is a vision shared by the International Air Transport Association (IATA) that represents some 240 airlines comprising 84 per cent of global air traffic. This will be achieved by investing in measures by the industry to cut emissions or by financing projects to cut an equivalent amount of emissions in other industries. However, it depends upon the ICAO setting CO₂ emission standards for new aircraft types, governments and fuel companies delivering sustainable aviation biofuels as also governments and air navigation service providers improving air traffic management (ATM) through comprehensive measures such as the Single European Sky and the US NextGen.

According to IATA, the key factor in carbon-neutral growth is fleet renewal. The next-generation of aircraft such as the Boeing B787 Dreamliner, Airbus A350 and Bombardier CSeries, are claimed to be 15 to 20 per cent more fuel-efficient than the current generation aircraft. This efficiency is primarily achieved through advanced engine technology, lighter airframe and supporting structures made of composite materials. It is also helped by better aerodynamic design, winglets, a “one-piece” fuselage and more advanced computer systems for optimising routes and payload. Airlines will need to spend around $1.5 trillion ( Rs. 75,00,000 crore) on new aircraft by 2020, which will result in a 21 per cent reduction in CO₂ emissions compared to a situation without fleet renewal. The existing fleet can also become more fuel-efficient by engine retrofits and modification of airframe through the latest technologies.

Airlines and airports can also lower emissions through improved operating procedures and weight reduction measures. Some of the more effective methods suggested to cut emissions are reduced auxiliary power unit (APU) usage, single-engine operation on the ground and adopting continuous descent approach (CDA) profile. Full implementation of more efficient ATM and airport infrastructure could provide an additional four per cent emissions reduction globally by 2020, while benefits could be as high as 10 per cent in some regions. However, the ultimate factor in attaining carbon-neutral aviation growth is the introduction of sustainable and commercially-viable alternative fuels. Recent tests on biofuels have indicated that a reduction of 80 per cent of CO₂ emissions on a full carbon life-cycle basis is possible. Many biofuels can be mixed with fossil jet fuel and used as drop-in fuels in current engines. As of June 2011, international aviation fuel standards allow commercial airlines to blend conventional jet fuel with up to 50 per cent biofuel.

Since there are just 1,700 major aviation fuel stations around the world, introducing alternative fuels should be a relatively smooth process. IATA has set a target of 10 per cent alternative fuels by 2017. The biggest challenge, however, is to find enough biomass to assure sufficient production for the aviation sector. A wide portfolio of second or third generation biofuel feedstock such as jatropha, algae and halophytes which do not compete with food crops for fresh water or land will be required. Projects to use municipal solid waste as feedstock to produce aviation fuel may also be beneficial. Improving the supply chain so as to reduce cost is essential to enable biofuel use to become more widespread. But at least for this decade and possibly beyond, high fuel costs as well as competing demands from other sectors of the economy make it unlikely that alternative fuels will deliver the promised aviation-related CO₂ reduction. Lastly, according to IATA, in order to close the gap, 90 million tonnes of CO₂ will need to be offset by 2025 to cap emissions at 2020 levels and achieve carbon-neutral growth.