A report that compares 14 net zero CO₂ transition roadmaps for the aviation sector has been published by The International Air Transport Association (IATA), with input from the Air Transportation Systems Laboratory at University College London (UCL), the Air Transport Action Group (ATAG), the International Council on Clean Transportation (ICCT) and the Mission Possible Partnership (MPP).  

The Aviation net zero CO₂ transition pathways comparative review aims to provide a ‘one-stop shop’ for airlines, policymakers and all aviation stakeholders to better understand the key similarities and differences between the various roadmaps, and their visions for achieving net zero carbon emissions for aviation by 2050. Factors compared include scope, input assumptions, modelled aviation energy demand, respective CO₂ emissions and the emissions reduction potential of each mitigation lever (new aircraft technologies, zero carbon fuels, SAF and operational improvements).

The analysis finds that possible pathways to net zero CO₂ emissions by 2050 differ significantly depending on the key assumptions of the authors regarding how decarbonisation technologies and solutions may evolve. However, all the roadmaps assume that SAF will be responsible for the greatest amount of CO₂ reductions by 2050. The role of SAF varies from 24–70% (with a median value of 53%). This wide range reflects the uncertainties regarding potential supportive government action, the level of investments, cost of production, and profit potential, as well as access to feedstocks.

The report also finds that technology and operational efficiency improvements are expected to have a similar role in the net zero transition across the roadmaps, together contributing to about 30% of the emissions reduction in 2050 in all scenarios.

Meanwhile, the estimated emissions savings by hydrogen and battery-powered aircraft vary greatly across the roadmaps, depending on whether a strong pro-hydrogen policy is adopted, and on whether there is a rapid decline in renewable energy prices, enabling swifter uptake of electricity-based technologies.

Lastly, to achieve net zero CO₂ emissions in 2050, almost all the global roadmaps suggest that the aviation sector will need help from market-based measures and carbon removals to address the residual emissions in 2050. Even if carbon removal technologies are considered an ‘out-of-sector’ mitigation measure, it is still both urgent and critical to develop these technologies, as CO₂ will be needed as feedstock for producing power-to-liquid (PtL) fuels.

Commenting on the report findings, Marie Owens Thomsen, IATA’s Senior Vice President Sustainability and Chief Economist, noted that unless there is ‘strong and urgent public policy support [in particular for SAF], no version of the roadmaps will get us to net zero carbon emissions by 2050’.

Boeing makes largest SAF purchase

In other news, Boeing has agreed to purchase 7.5mn gallons (over 22,700 tonnes) of blended MY SAF fuel from Neste in 2024 to support the Boeing ecoDemonstrator programme as well as to support efforts to reduce greenhouse gas (GHG) emissions from its US commercial operational flights this year. The deal represents the airline’s largest annual SAF purchase to date, 60% more than in 2023.

The Neste fuel blend consists of 30% SAF, made from renewable waste and residue raw materials such as used cooking oil, and 70% conventional jet fuel. According to Neste, its SAF reduces greenhouse gas emissions by up to 80% when used in unblended form (according to life cycle assessment methodologies such as CORSIA) over the fuel’s life cycle, compared to using conventional jet fuel.  

At present about a fifth of Boeing’s fuel use is a SAF blend.  

Neste has also signed an agreement with Air New Zealand for the supply of 2.4mn gallons of neat MY SAF for delivery in 2024. To be produced at Neste’s Singapore refinery, which expanded its SAF production capability last year and is currently ramping up production, the neat SAF will be blended with conventional jet fuel to meet the required fuel specifications and supplied to Los Angeles International Airport.

World’s first sewage-to-SAF plant

Meanwhile, UK biofuels company Firefly Green Fuels has unveiled plans to develop what is claimed will be the world’s first commercial-scale factory turning human waste into SAF. The plant is to be based in Harwich, Essex, and is slated to start delivering fuel by 2028.  

Recently signed memoranda of understanding relating to the project include an agreement with Anglian Water to provide the biosolids, a product of its wastewater treatment process as part of the initial pilot phase; and one with flight operator Wizz Air to provide up to 525,000 tonnes of SAF over 15 years. According to Firefly, independent analysis by Cranfield University has shown that its SAF offers a 92% CO₂e saving versus fossil jet fuel.

First airside hydrogen refuelling trial in UK

In related aviation news, the UK’s first airport airside hydrogen refuelling trial in the UK has concluded successfully at Bristol Airport. Project Acorn involved refuelling and powering the baggage tractors servicing easyJet passenger aircraft, as part of the airline’s daily operations. It aimed to demonstrate that hydrogen gas can be safely and reliably used to refuel ground equipment, enabling airlines to transition to more sustainable fuels and reduce their carbon footprint.

Involving organisations including Cranfield Aerospace Solutions, Cranfield University, Connected Places Catapult (CPC), DHL Supply Chain, Fuel Cell Systems, the IAAPS research institute, Jacobs, Mulag and TCR from across aviation, engineering, logistics and academia, the outputs of the trial are to now be used to help develop industry best practice standards, provide guidance to airports, airlines, local authorities and regulators on required infrastructure changes, and support the development of a regulatory framework for hydrogen’s use on an airfield – standards which, due to hydrogen’s novelty in aviation, do not currently exist.