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ISSN 2753-7757 (Online)

A matter of quality: reducing greenhouse gas emissions from aviation

30/11/2022

8 min read

Aircraft refuelling truck parked by airplane Photo: Neste
Over the past year, the EI has worked with over 40 organisations, including eight synthetic fuel manufacturers, to address perceived technical barriers to the widescale deployment of synthetic jet fuel in supply chains

Photo: Neste

Replacing the fossil fuels in the aviation sector is recognised to be a serious challenge. Here, Martin Hunnybun, the Energy Institute’s (EI) Head of Sustainable Fuels, describes the latest quality assurance initiatives for handling synthetic jet fuel in aviation supply chains as the sector aims to move towards net zero.

Progress in reducing greenhouse gas (GHG) emissions from aviation fuel is extremely slow. In 2019 some 95bn gallons of jet fuel were consumed globally, emitting about 915mn tonnes of CO2. Consumption figures are expected to reach at least 450bn gallons of jet fuel by 2050. Despite this, the sector is fully committed to meeting net zero targets by 2050.

 

Indeed, in October 2021 the International Air Transport Association’s  (IATA) 77th Annual General Meeting approved a resolution for the global air transport industry to achieve net zero carbon emissions by 2050. More recently this was also set as the worldwide climate goal for aviation at the United Nation’s 41st Triennial International Civil Aviation Organisation (ICAO) assembly in October 2022.

 

A conclusion of the Waypoint 2050 study back in September 2020 from the Air Transport Action Group was that 80% of the aviation sector’s GHG emissions come from flights greater than 1,500 km, for which there is no alternative mode of transport. Couple this with the value of airframes and engines and their extended operational life (more than twice that of an average car) and the ongoing need for energy dense liquid fuel from a renewable source becomes clear.

 

Technical stakeholders have worked collaboratively for over 20 years to assess the viability of using kerosene that has been synthesised from renewable feedstocks rather than fossil sources. Standardisation activity and leadership from the US Federal Aviation Administration have resulted in approval of seven, soon to be eight, feedstock/processing pathways to produce synthetic jet fuel, suitable for use with existing airframes/engines without any need for hardware recertification. The standardisation requirements for manufacture ensure that these fuels can also be handled in all of the same ground facilities.

 

This drop-in solution promises deep cuts in GHG emissions from the aviation sector in the next two decades, despite the sector’s continued growth.

 

two airplanes flying in blue sky through white clouds

Technical stakeholders have worked over 20 years to assess the viability of using synthetic jet fuel from renewable feedstocks rather than fossil sources  
Photo: Neste

 

EI resource helps with roll-out   
The EI’s Aviation Committee maintains a portfolio of over 50 resources on fuel handling to help control aviation fuel quality and its safe and efficient deployment for the 100,000/day commercial flights worldwide (see full listing at EI Aviation Collection).

 

One EI publication, EI/JIG Standard 1530 Quality assurance requirements for the manufacture, storage and distribution of aviation fuel to airports, first described the handling of synthetic jet fuel in 2013. In the last 12 months the EI has worked with over 40 organisations, including eight synthetic fuel manufacturers, to address perceived technical barriers to the widescale deployment of synthetic jet fuel in supply chains.

 

EI 1533 Quality assurance requirements for semi-synthetic jet fuel and synthetic blending components was launched at the IATA Aviation Energy Forum in New Delhi, India, on 17 November 2022. As well as details of the current seven standardised pathways to produce synthetic jet fuel, it provides requirements and recommendations for handling of synthetic blend components, blending with conventional jet fuel/jet fuel components from fossil sources and handling the blended semi-synthetic jet fuel.

 

A focus of the publication is to provide details on blending. It is a requirement of the governing specification, ASTM D7566, that the synthetic blending component (from a renewable feedstock) is blended with jet fuel/jet fuel blending components that are derived from conventional fossil sources.

 

In most cases, there is no technical justification for this step from a fuel properties perspective. However, it is the means by which the engine and airframe manufacturers are able to derive in-service experience and confidence in the effectiveness of the controls provided by the governing specification. Currently, no synthetic blending component is allowed to be used at more than 50% in semi-synthetic jet fuel.

 

The publication describes how caution is required in the selection of synthetic blend components and conventional jet fuel for blending, to ensure that the properties of the semi-synthetic jet fuel meet the specification and it is fit-for-purpose. EI 1533 also describes the facilities required for the blending process to ensure that sufficient mix energy is provided. Such infrastructure will need to be more widely deployed to meet the ambitious targets for the ramp up of semi-synthetic jet fuel.

 

A list of the topics covered by EI 1533 is shown in the Box below.

 

Topics covered in EI 1533 Quality assurance requirements for semi-synthetic jet fuel and synthetic blending components

  • Manufacture of synthetic blending components.
  • Export/import and transport of synthetic blending components: handling, testing, product integrity.
  • Semi-synthetic jet fuel manufacture (blending): constraints, homogeneity.
  • Semi-synthetic jet fuel import/export: handling, testing, traceability.
  • Design requirements – blending equipment, positive segregation.
  • Managing semi-synthetic jet fuel at airports.


What’s in a name?   
During the preparation of the publication, one aspect that was identified as being critical to effective quality assurance was the consistent and correct use of terminology.

 

Many communications on this topic refer to ‘sustainable aviation fuel (SAF)’ – a term that some apply to the ‘synthetic blend component’. No aircraft are certified to fly on the synthetic blend component alone. It actually has to be blended with conventional jet fuel/components from fossil sources to form a semi-synthetic jet fuel (which some also refer to as SAF).

 

As in this article, EI 1533 advocates the use of two terms to maintain the distinction between a blending component that is not acceptable to uplift to an aircraft, and a fuel that is. See Fig 1.

 

graphic showing use of two terms to specify the distinction between a blending component that is not acceptable to uplift and aircraft, and a fuel that is

Fig 1: EI 1533 advocates the use of two terms to specify the distinction between a blending component that is not acceptable to uplift and aircraft, and a fuel that is  
Source: Energy Institute

 

Terminology is set to become more important in the coming months as engine and airframe manufacturers conclude their work to approve the first fully synthetic jet fuel for use with all existing equipment/handling systems as a ‘drop-in’ solution. It will not be required to be blended with any conventional fossil fuel, enabling much greater reduction in GHG emissions. This will also be covered by the generic term SAF.

 

With its fuel-handling/quality assurance focus, EI 1533 intentionally avoids the assessment of sustainability. The synthetic pathways defined by ASTM D7566 similarly avoid this and indeed include one pathway from coal/gas (CNG/LPG) to kerosene. The assessment of sustainability for renewable feedstocks is covered in detail elsewhere. Two examples are the Roundtable on Sustainable Biomaterials (rsb.org) and International Sustainability and Carbon Certification (iscc-system.org).

 

All stakeholders worldwide are encouraged to make reference to EI 1533, which as a supplement to EI/JIG Standard 1530 becomes part of the cornerstone of jet fuel quality control from refinery to airports.

 

Although emissions from ground handling operations at airports contribute a tiny fraction of the total emissions from aviation, they are emissions that can be rapidly minimised.

 

On the ground   
All technical committees within the EI’s Technical & Innovation area were challenged several years ago to find ways to minimise GHG emissions from all existing operations. This led the Aviation Committee to review current ground-handling arrangements at airports and consider what reductions could be offered by the use of alternative fuelling equipment.

 

Although emissions from ground handling operations at airports contribute a tiny fraction of the total emissions from aviation, they are emissions that can be rapidly minimised. European airports have committed through Airports Council International Europe (ACI Europe) to achieve net zero carbon emissions (for operations under their control) at the latest by 2050, with the deployment of renewable electricity being the focus for those locations.

 

Most of the commercial aircraft fuelling operations worldwide utilise diesel-powered refueller vehicles or hydrant dispenser vehicles to deliver aviation fuel. The EI’s Aviation Committee commissioned the global environmental consultancy Ricardo to assess how the adoption of different technologies to refuel aircraft could cut GHG emissions, including life cycle analysis, not only operational emissions.

 

The EI research report was published in October 2022 (as reported in New Energy World, 26 October). It documents the GHG emissions associated with aircraft refuelling at a large commercial case study airport in 2019 and estimates the emissions for the same fuel uplift volume/number of fuelling operations using alternative approaches.

 

Assessments included engine off technology for hydrant dispensers, the use of hydrogenated vegetable oil (renewable diesel), the deployment of hydrant carts for refuelling narrow-body aircraft, the use of electrically powered pump off for refuellers and the adoption of fully electric hydrant dispensers and refuellers.

 

The findings were compelling (see example in Fig 2). The largest GHG emission reductions were found to be achieved through the adoption of fully electric hydrant dispensers and refuellers (83% and 84% respectively if the vehicle charging point is supplied by renewable electricity; 48% and 49% based on the current average for the EU grid) and, where operationally feasible, the use of static hydrant carts for servicing narrow-bodied aircraft (92% reduction).

 

graphic of annual GHG emissions per aviation stand

Fig 2: Annual GHG emissions per aviation stand – hydrant dispensing technologies  
Source: Ricardo/EI research report

 

Using renewable diesel was also found to provide an impactful near-term pathway to decarbonisation of some existing vehicle fleets, with reductions of operational GHG emissions of between 65% and 90% if sourced sustainably.

 

However, as government policies in Europe prioritise low-carbon fuels for the aviation and marine sectors, such fuels are likely to be a short-term solution only for ground handling operations.

 

The report provides a benchmark to help stakeholders assess which measures would produce the largest GHG emission reductions for their operations – the data in the report being applicable to large hub airports with fuel hydrant systems as well as regional airports with refueller operations.

 

Speed of transition   
It is widely understood that there needs to be a rapid reduction in GHG emissions from the aviation sector (despite it accounting for only 3% of anthropomorphic emissions annually). This can be achieved by approaches available today. The task facing the industry is to scale up and widely deploy semi-synthetic jet fuel (and fully synthetic jet fuel when it is approved in the near future) using electrically powered hydrant dispensers and refuellers.

 

The two new resources from the EI are intended to help expedite this so that the global connectivity provided by the aviation sector can continue to expand, including to all of society.