[Analysis] Indian aviation’s turbulent path to sustainability

Even as the climate crisis casts an ever-lengthening shadow, India’s aviation industry is poised for a dramatic takeoff.

As passenger numbers in India are expected to climb 7% annually, Air India and IndiGo, two of India’s aviation giants, are gearing up to meet the surging demand. In February this year, Air India set a record by ordering 470 new aircraft, scheduled for delivery over the next decade. This move will increase its current fleet of 124 aircraft nearly five-fold by 2033. Not to be outdone, IndiGo Airlines announced an order for 500 new Airbus aircraft four months later. With a previous order of 480 aircraft still pending delivery, IndiGo’s fleet size will increase by almost 1000 in the next decade for a four-fold increase over its current fleet strength of around 300 aircraft.

However, amidst these ambitious growth strategies lies an unsettling reality – the aviation industry’s carbon footprint, a consequence of its carbon-intensive nature, is set to increase significantly.

We conducted an analysis that considers multiple scenarios for Indigo and Air India, taking into account their historical performance, market shares, and fleet expansion plans. While we have presented a simplified summary here, our detailed calculations, done for the purpose of this analysis, support our projections.

Between 2013 and 2023, IndiGo witnessed remarkable growth, with its passenger base expanding at an impressive compound annual growth rate (CAGR) of 18%, which we arrived at using data from the Directorate General of Civil Aviation (DGCA) website for the years 2013-2023 to calculate the passenger growth rate, specifically for IndiGo Airlines.

However, it is unlikely that IndiGo can sustain such a high growth rate in the future. We conservatively estimate that IndiGo’s growth will considerably slow down to a CAGR of about 10% in the next decade, with their ambitious expansion plans leading to a rise in market share but at a considerably slower pace than in the previous decade.

Despite this adjustment, the airline will experience a considerable increase in passengers, swelling from the current 86 million in 2022-23 to over 220 million in the next ten years.

In 2022-23, IndiGo’s greenhouse gas (GHG) emissions stood at 6.7 million tonnes. However, with the expected growth, we anticipate IndiGo’s annual emissions to rise to 12.5 million tonnes in the next decade, even with anticipated improvements in fuel efficiency from the adoption of new aircraft and optimistic assumptions about potential reductions through the use of ‘Sustainable Aviation Fuel.’

Concurrently, we project Air India’s annual CO2 emissions to rise from about 2.8 million tonnes in 2023 to over 5.5 million tonnes in 10 years despite the fuel efficiency of new aircraft. This projection is contingent upon our assumption that Air India’s ambitious five-fold expansion plan will halt its market share decline and stabilise it. To achieve this stabilisation, we assume that Air India will match the all-India passenger growth rate of 7%.

In summary, we estimate that the combined annual emissions from these two carriers alone would rise to at least 18 million tonnes in the next decade, greater than the emissions of the whole country of Ethiopia in 2021.

Moreover, the impact of flights is considerably larger than the direct climate impact of CO2 emissions. Contrails, formed from aircraft exhaust in cold high altitudes, can evolve into cirrus clouds, both of which trap outgoing heat and amplify aviation’s warming impact on the climate. The IPCC AR6 has assessed that for a 20-year time horizon, the net global warming potential (GWP) of aviation is staggeringly four times that of CO2 emissions alone.

Unambitious mitigation plans

Unfortunately, the ambitious expansion plans of these carriers are matched by their lack of ambition in mitigating the environmental consequences of expansionism. Our analysis reveals a conspicuous absence of credible emission reduction plans from either carrier. To its credit, IndiGo publishes annual reports setting out its GHG and particulate matter emissions, as well as its current and planned social and environmental initiatives. In contrast, Air India has placed little data in the public domain and none about its GHG emissions.

The few plans mentioned by these carriers largely focus on emissions from fuel used for ground operations. For instance, Air India has introduced Taxibots to reduce fuel consumption for on-ground operations and IndiGo has electrified its on-ground units. However, emissions from ground operations amount to only about 1% of an airline’s total emissions; 99% of emissions result directly from fuel used by aircraft, for which the mention of mitigation is astonishingly little.

We emailed both carriers to inquire about their emissions and future emission control plans, but we have not yet received a response.

Beyond the blue sky

The most commonly mentioned strategies for mitigating airline emissions, as also noted in IndiGo’s 2022-23 ESG report, are the adoption of so-called ‘Sustainable Aviation Fuels’ (SAF) and using ‘carbon offsets’. We, therefore, analyse the technical viability and scope of these strategies in detail.

‘Sustainable Aviation Fuel’ (SAF) is blended and used with conventional jet fuel and is touted as a ‘sustainable’ alternative to conventional jet fuel because of reduced lifetime emissions. It is made of various sources of feedstock and biomass, meant to be used as a “drop-in” fuel, requiring no changes to the aircraft and infrastructure.

Depending on the combination of materials used to manufacture it, it is claimed that certain kinds of SAF can reduce emissions up to 80% relative to the baseline scenario of no SAF. However, more grounded scientific projections of their technical feasibility have found that even under their most optimistic scenario, SAF may reduce fleet-wide airline emissions only by 23% by 2050 relative to 2005 levels. Regardless, as Indigo acknowledges, they expect to use a maximum blend of 10% SAF by 2030, which would lead to their total absolute emissions being lower by, at most, 8%, even in the most optimistic scenario relative to not using SAF. Our estimates of IndiGo’s future emissions have internalised optimistic SAF reductions.

It is important to note that SAF is an untested technology at scale: it is not presently under mass production and faces supply constraints. It is also three to four times more expensive than kerosene jet fuel, disincentivising airlines from incorporating high levels of SAF blended fuel. It is expected that costs will fall substantially as production capacity is increased. However, new challenges are likely to emerge as production scales up.

Depending on the feedstock used to produce a particular type of SAF, it can precipitate several harmful impacts. For instance, if a previously food-producing land is repurposed for SAF feedstock cultivation, it could displace food production to a new area, potentially causing deforestation or land degradation. It can result in water pollution, too, due to the runoff of fertilisers and pesticides.

Given these concerns, establishing credible certification programs for SAF fuels will be essential. Unfortunately, recent research has found the global REDD+ certification programme for carbon offsets, which could have served as a blueprint for SAF certification, dangerously unfit for purpose.

‘Carbon offsets’ are commonly presented as a viable solution for counterbalancing greenhouse gas emissions. By purchasing ‘carbon offset credits’, an emitter effectively funds positive environmental actions taken by another party, which can encompass a range of initiatives such as renewable energy projects and afforestation. In reality, however, offset projects have been beset with serious problems.

A study published in Science found that over 90% of rainforest carbon offsets certified by Verra, the world’s leading carbon standard for the so-called ‘voluntary offsets market,’ were worthless. These offsets were purchased by some of the largest corporations in the world, including Disney, Shell, and Gucci, to claim emissions reduction. Closer home, a new report just released by the Centre for Science and Environment has revealed troubling details about offset projects in India.

In effect, carbon offset schemes have evolved into a carte blanche for polluters to perpetuate their pollution while evading accountability for the inadequate success of these offsets. The same fate may await prospective SAF certification schemes of the future.

How much would it cost carriers to offset their emissions credibly? Direct Air Capture (DAC) is one of the most significant technologies that verifiably satisfies most of the requirements for a credible offset project. It works by filtering carbon dioxide directly from the atmosphere and storing it in underground geological formations.

DAC is technically feasible but is currently operating at a small scale. The largest operational project in Iceland sequesters 4000 tonnes of carbon dioxide a year – amounting to barely half the personal carbon footprint of just one billionaire – Bill Gates. DAC is currently extremely expensive, priced at $ 600-800 per tonne of carbon dioxide. However, even if we make generous assumptions of DAC scaling up to sequester millions of tonnes over the next decade and its price dropping to $100 per tonne, it would still collectively cost Air India and IndiGo a staggering $1.8 billion per year to offset their emissions using DAC. This thought experiment illustrates the true cost of credible and transparent emission reduction.

Another way to reduce emissions is through the electrification of aircraft using batteries or hydrogen fuel. However, their prospects for use in aviation are limited by fundamental physical constraints aside from economic and logistical ones.

Even the latest generation commercial batteries have an energy density that is an order of magnitude lower than conventional fossil fuels. State-of-the-art Tesla batteries yield less than 400 Wh/kg (watt-hours per kg), whereas conventional jet fuel yields nearly 12,000 Wh/kg, making batteries 30x heavier than jet fuel for equivalent energy output. Hydrogen, on the other hand, contains high gravimetric energy density but is characterised by a very low density at room temperature, requiring very large storage volumes and heavy tanks.

Both these are major limitations for aircraft, where compactness and low overall weight are needed due to limited space and the imperative to not increase the required propulsion power.

Airline responsibility and the wider systemic context

The preceding discussion revolves around the implicit assumption that Indian air carriers bear responsibility for their carbon emissions. However, there is a compelling argument that may appear to challenge this assumption. The primary responsibility for the current global warming crisis lies with the Global North since they have contributed most of the cumulative anthropogenic carbon emissions in the industrial period. From this standpoint, it is unjust to assign the burden of climate change mitigation to the Global South, including entities within it.

While we agree with this argument both factually and morally, we maintain that it does not absolve Indian air carriers of their moral responsibility to mitigate their emissions. Climate change is often framed as an “anthropogenic” issue but may be more accurately described as a problem stemming from the extravagant consumption patterns of the world’s affluent minority. Few choices epitomise luxury as clearly as the transportation choices available to us, particularly the option of air travel.

From this perspective, the profitability of air carriers is derived from offering a luxury service to a privileged minority. This becomes particularly evident in the private charter services offered by several Indian airlines, including IndiGo and Air India Express.

In our view, profiting from luxury consumption, especially when facilitating it, carries an inherent moral obligation to address the resultant impacts.

While highlighting these concerns, we want to underline the imminent environmental challenges confronting Indian airlines as they grapple with rapid growth, emissions, and sustainability concerns. However, it is essential to recognise that these challenges are not restricted to the issue of airline emissions alone but are symptomatic of the broader economic system reliant on perpetual economic expansion. An increasing body of scientific work has powerfully linked economic expansionism with escalating climate and ecological damages.

To truly prioritise sustainability, we must embark on a profound reassessment of this system, including the role of businesses within it. This necessitates a shift away from a model, driven solely by expansion and profit towards one that places genuine social progress and environmental conservation at its core.

Chirag Dhara is a physicist and climate scientist at Krea University, a lead author of the Indian Climate Assessment Report (2020) and contributing author to the IPCC AR6 WG1’s Atlas (2021). Litisha Bagadia is a high school senior with a deep interest in the circular economy and climate action. Tanvi Kadakol is a graduate in Environmental Studies with a keen focus on ecology, climate change, and fostering sustainable transitions.

Banner image: Aircrafts await takeoff clearance at Mumbai airport. Photo by Wireman27/Wikimedia Commons.