How realistic is the Sustainable Aviation net zero goal?

The number of flights by the airline industry globally, reached a staggering 38.9 million in 2019, just prior to the Covid-19 pandemic. 

The following year, unsurprisingly, saw a significant decline but in 2023 the figure had reached 36.8 million flights. 

The environmental costs of soaring demand

It is generally held that aviation accounts for 2.5% of global CO2 emissions and has contributed around 4% to global warming to date when directly related services and other warming influences (such as contrails) are taken into account. 

Currently, approximately 10% of the world’s population flies in most years. Rising incomes suggest that figure will increase, although there are mitigating factors such as geo-political unrest and armed conflicts. 

According to OurWorldInData, between 1990 and 2019 (the pre-pandemic year) air passenger and freight demand quadrupled. During that time, flying became twice as energy efficient due to improved design and technology, larger aircraft and capacity planning leading to reductions in the number of empty seats. 

The carbon intensity of aviation fuel had not changed. As a consequence, during that period, CO2 emissions roughly doubled. Clearly this trajectory is unsustainable from a climate change perspective.

Challenges loom for aviation’s net zero ambitions

One of the leading aviation organisations, IATA (the International Air Transport Association), representing more than 300 of the world’s airlines, has declared an ambitious target for its members to collectively achieve net zero emissions by 2050. 

As an indicator of the feasibility of such targets, it is worth noting that Air New Zealand recently cited shortages of sustainable aviation fuel and more sustainable aircraft supply issues as reasons for it not being able to meet its 2030 emissions target, although the airline claims it intends to keep to its 2050 goal. The sustainable aviation fuel shortage may seem surprising, given the global demand this year will be, according to IATA, just 0.5% of total fuel requirements. 

Added to this, Boeing, under increased pressure from regulators, has slowed production in order to improve quality, whilst Airbus is so stretched it has been declining orders. It is anticipated that next-generation jets will consume 15-20% less fuel but the delivery wait-times are likely to be many years. 

Alongside ambitious CCS targets, the IATA Infrastructure Roadmap relies for achieving its 2050 net zero goal, on SAF production exceeding 400 Mt/year by 2050, and Hydrogen production for SAF approaching 100 Mt/year. 

Not only are the technologies still relatively in their infancy, making achievement of these targets difficult to imagine, but in the case of Hydrogen, its combustion in aircraft would produce around 2.6 times more water vapour than kerosene fuel, which in turn would add to the global warming effect. Even if these technologies can be scaled to the degree necessary, the investment required by the aviation industry alone to meet the 2050 net zero ambition is eyewatering – estimated by IATA at $5 trillion by 2050 or approximately $180 billion per year from 2023 to 2050. 

As IATA’s own projections for SAF growth has been reduced, as current SAF production is estimated at 1.5 million tonnes and as CCS is growing less rapidly than many had hoped,, the 2050 net zero goal is looking like a mountain to climb.