Decarbonisation is one of the biggest challenges faced by aviation, and the pathway to net-zero emissions will take innovation, collaboration, and legislation.
Britain is asking countries to push for a global target to cut aviation emissions to levels compatible with the Paris Agreement, under a deal due to be announced at the COP26 climate change summit, according to a draft document seen by Reuters.
As COP26 host, Britain is rallying countries to join an “International Aviation Climate Ambition Coalition” and agree to push the United Nations’ aviation agency to set a long-term target to reduce emissions from international flights.
Countries that sign the deal would commit to supporting the adoption by the UN’s International Civil Aviation Organization (ICAO) of an “ambitious long-term aspirational goal that is compatible with net-zero global emissions by 2050”, the draft said.
The aim is to build momentum for ICAO to set tougher climate targets when its nearly 200 member countries meet in September 2022.
It’s worth highlighting that the Paris Agreement does not explicitly address international aviation emissions, but commits countries to limit global temperature increases to 2C this century and aim for 1.5C. To meet the 1.5C goal, which would avoid the worst impacts of climate change, scientists say combined global CO2 emissions from all sectors would need to be reduced to net zero by 2050.
Montreal-based ICAO, the UN body for aviation, is facing pressure to toughen its climate goals. UN Secretary-General Antonio Guterres this month blasted the agency’s plans as too weak and urged it to set “more ambitious and credible targets”.
“Current commitments are not aligned with the 1.5-degree goal of the Paris Agreement. In fact, they are more consistent with warming way above 3 degrees,” Guterres said, referring to both ICAO and the UN shipping agency’s climate aims. ICAO sits at the centre of a global system of widely agreed policies but is not a regulator in its own right.
Commercial aviation continues to be responsible for about 2-3% of global carbon emissions. The World Wildlife Fund describes aviation as “one of the fastest-growing sources of the greenhouse gas emissions driving global climate change.” It adds that air travel is “currently the most carbon intensive activity an individual can make.”
But to date, the industry has made most progress on efficiency gains on new aircraft. Today around 85% more efficient than those entering service in the 1960s.
For electric flying – the wider goal of the sector – a key challenge in building electric aircraft involves how much energy can be stored in each amount of weight of the on-board energy source. Although the best batteries store about 40 times less energy per unit of weight than jet fuel, a greater share of their energy is available to drive motion.
Jet fuel contains about 14 times more usable energy than a state-of-the-art lithium-ion battery. This makes batteries very heavy for aviation – and that’s an issue the sector is still grappling with today. When you combine this with the fact that aviation is always aggressively trying to offload extra weight onboard (whether it’s through the installation of light-weight-slimline seats, fewer onboard bathrooms, the removal of onboard literature, etc) you begin to realise just how much of a challenge this is.
The use of sustainable aviation fuel will help meet the regulatory standards on emission and reduce carbon emission due to the rising air traffic. The effective application of low carbon technologies, such as electric and hydrogen propulsion are unlikely to be in widespread use until 2040 or later, meaning Sustainable Aviation Fuel (SAF) provides one of the only viable ways to reduce aviation emissions significantly in the short to medium-term.
Based on the type of feedstock used, sustainable aviation fuel gives a remarkable reduction in carbon emission compared to conventional jet fuel. Thus, to achieve the target of greenhouse gas emissions reduction, the demand for sustainable aviation fuel is growing significantly.
Sustainable aviation fuel (SAF) is the main term used by the aviation industry to describe “non-conventional” aviation fuels that are produced from sustainable feedstocks.
There are currently five internationally approved processes through which SAFs can be produced. Each of these pathways has its benefits, such as the availability of feedstock, cost of the feedstock, carbon reduction or cost of processing. Some may be more suitable than others in certain areas of the world. But all of them have the potential to help the aviation sector reduce its carbon footprint significantly, assuming all sustainability criteria are met.
One type of SAF, for example, uses waste fat and oils. It is the most commercially available type of SAF today – used in about 95% of the 300,000 SAF powered flights that have flown since 2016.
It is a “drop in” solution – currently blended with conventional fuels at various percentages, can use the same supply infrastructure, and does not require engine or aircraft modifications to work. First used by the industry in 2008, SAF has powered over 250,000 flights around the world. However, volumes currently remain low, with SAF accounting for less than 0.1% of the aviation fuel market.
If used neat, SAF has the potential to reduce life-cycle emissions by up to 80%. It works just like conventional jet fuel, in that it combusts inside an engine, hence producing emissions. It is ‘sustainable’ because it emits less CO2 over its lifecycle.
British Prime Minister Boris Johnson said on Tuesday that current global targets around sustainable aviation fuel were “pathetic” and that the world could do more as he announced plans to drive the adoption of green technology globally.
While admitting the challenge was a “tough nut to crack”, he said “guilt free aviation” was possible, citing a joint deal with billionaire philanthropist Bill Gates to spend £400mn ($545.04mn) on the problems of low-carbon aviation.
Currently, SAFs are more expensive than traditional jet fuel. Estimates range from 2x for some waste-based sources to 6-10x for synthetic fuels using carbon capture. This is mainly due to the small production runs. However, further production facilities are being constructed or planned, and multiple airlines are signing significant forward purchase agreements which help provide offtake certainty to new energy suppliers, allowing them to finance new plants. This will help bring down the cost of SAFs in the mid- to long-term.
Several airlines are driving forward the use of SAFs by signing multi-million dollar forward purchasing agreements. Others have invested in start-up support for SAF deployment, and some have promoted SAFs through test flights, research, and investigation of local opportunities. Five airports also have a regular SAF supply: San Francisco, Los Angeles, Oslo, Bergen, and Stockholm.

Source: Civil Aviation Authority – Qatar