How sustainable is flying?

Although the proportion of carbon emissions from global civil aviation is growing, it is still only 4% of total emissions and about 14% of carbon dioxide pumped into the atmosphere from the transportation sector, far behind road transport.

According to the International Air Transport Association (IATA), the airlines around the world will emit nearly 1 billion tonnes of CO₂ emissions in 2024. Biofuels are being tested on airlines, but battery-powered aircraft are still in the experimental stage.

For the time being, the only way to reduce emissions from the aviation sector is to travel less, but that is not feasible in an increasingly interconnected world. The next option is to increase the proportion of biofuels, but this could lead to a shift away from farming for food and also be more water-intensive. Passengers can also buy carbon credits in renewable energy projects to offset their emissions during flights.

For the moment the most sustainable option is to make aircraft engines more efficient, and this is already happening with jet and turboprops today burning much less fuel per passenger/km than the previous generation of power plants.  

The most popular aircraft in Nepal’s domestic aviation is the ATR72-500 aircraft with Buddha Air alone operating 17 of the model. The French-Italian turboprop aircraft revolutionised sustainable flying by being the most fuel-efficient medium-range plane since it first flew in the 1980s.

Newer models of ATRs are even more fuel efficient. The latest ATR 72-600, for example, is even more efficient because of its lighter build, high performance and reduced emissions, making it the most fuel-efficient as well as cost-efficient regional plane flying today.

The ATR 72-500 with its twin engines burns around 130kg of fuel per hour, depending on factors like weather, altitude, and how much cabin air conditioning is needed. This is a huge improvement in fuel efficiency compared to other turboprops and even older generation ATRs.   

Besides CO₂ aircraft exhaust also contains other greenhouse gases like nitrogen oxides, water vapour and sulphates which are emitted at high altitudes. A EU study has also shown that non- CO₂ impacts of aviation to be almost as important as of carbon dioxide alone. Since the ATR is a European manufactured aircraft it will have to comply with the European Green Deal target to reduce transport emission by 90% by 2050, and some of that reduction has to come from aviation.

‘At ATR, we are committed to reducing our greenhouse gas emissions to contribute to net-zero carbon emissions by 2050,’ the ATR website says, adding that it will be using 100% sustainable aviation fuels (SAF) by 2025.

The manufacturer is also installing new Pratt & Whitney PW127XT turboprops on its new planes, lowering fuel consumption further. Its EVO version will incorporate hybrid capabilities.

These innovations will take some time to arrive in Nepal, but even the fact that domestic airlines like Buddha are switching to ATR-72 translates into considerable savings in fuel burn. Besides Buddha Air, other domestic airlines operate 4 ATR-72s, and there are at least five more on order.