Measurement and testing
Sustainable Aviation Fuel (SAF) is currently regarded as the most practical solution for reducing greenhouse gas emissions in aviation.
Because SAF can be used in existing aircraft engines and infrastructure, global investments in SAF production technologies are increasing rapidly.
Modern SAF plants require advanced process analytics to ensure stable operation, optimised yields, catalyst protection, and compliance with strict fuel specifications.
This article provides a short overview of current SAF market developments, explains the Alcohol-to-Jet (AtJ) and Hydrotreated Vegetable Oil (HVO/HEFA) pathways, and discusses the analytical technologies and sampling systems used in industrial SAF production.
The global target of achieving net-zero emissions by 2050 has accelerated investments in renewable fuels and low-carbon industrial technologies.
Aviation is considered one of the most difficult sectors to decarbonise because aircraft require fuels with very high energy density.
As a result, Sustainable Aviation Fuel (SAF) has become the central focus of many airline and refinery decarbonisation strategies.
Governments and international organisations are supporting SAF development through regulatory mandates and incentive programs such as ReFuelEU Aviation, CORSIA, and the U.S. Sustainable Skies Act.
Countries including Japan, Indonesia, India, and China have also announced national SAF blending targets.
Despite strong market growth, current SAF production volumes still represent only a small percentage of global jet fuel demand.
Most commercial projects today are based on HEFA/HVO technology because these processes are technically mature and can often be integrated into existing refinery infrastructure.
Alternative pathways such as Alcohol-to-Jet (AtJ), Fischer-Tropsch (FT), and Power-to-Liquid (PtL) are expected to gain importance in the coming years.
The rapid increase in SAF investments has created growing demand for advanced process analytics.
Modern SAF plants require continuous monitoring of feedstocks, hydrogen recycle streams, reactor conditions, impurities, off-gases, and final product quality.
Online analytical systems help operators optimise yields, reduce energy consumption, protect catalysts, and avoid off-spec products.
The Alcohol-to-Jet pathway converts renewable alcohols such as ethanol or isobutanol into synthetic aviation fuel components.
In ethanol-based AtJ processes, ethanol is first dehydrated to ethylene.
The ethylene molecules are then oligomerised into longer hydrocarbon chains before a final hydrogenation step stabilises the product and adjusts the required fuel properties.
The AtJ process benefits from well-established catalytic technologies from the petrochemical industry and offers high flexibility regarding feedstock sourcing.
However, reaction selectivity and hydrocarbon chain distribution must be carefully controlled because even small deviations can significantly influence final fuel quality.
Process analytics therefore plays a central role in AtJ plants.
Gas chromatographs are typically installed to monitor ethanol purity, ethylene concentration, olefin composition, paraffin distribution, and product fractionation.
Continuous analytical monitoring allows operators to optimise catalyst performance and maximise jet fuel yield.
The HVO or HEFA pathway is currently the dominant commercial SAF technology.
Typical feedstocks include vegetable oils, used cooking oil, animal fats, and other lipid-based waste streams.
The process consists mainly of hydrotreating through deoxygenation reactions, followed by hydroisomerisation, and in some configurations, hydrocracking.
During hydrotreating, oxygen is removed from the renewable feedstock using hydrogen under elevated temperatures and pressures.
The resulting hydrocarbons are subsequently converted into renewable diesel and SAF fractions.
Because HVO plants operate with large hydrogen recycle streams and high active catalysts, continuous process monitoring is essential.
Online analysers are used to monitor hydrogen concentration, sulphur compounds, H2S, carbon oxides, and hydrocarbon composition.
The analytical systems support optimisation of hydrogen consumption, stabilisation of reactor operation, and protection of catalysts against contamination.
Process analytics is essential for stable and economically optimised SAF production.
Online analysers provide real-time information about feedstock quality, reaction conditions, impurities, and final product composition.
Gas chromatography (GC) is one of the most important analytical technologies used in SAF plants because it offers highly selective multi-component analysis with excellent repeatability.
In AtJ processes, GC systems monitor ethanol purity, ethylene concentration, olefin composition, and paraffin distribution.
In HVO plants, gas chromatographs analyse hydrogen recycle gas, light hydrocarbons, H2S, sulphur compounds, and stabiliser off-gases.
Typical analyser applications are shown in table 1.
In addition to GC systems, Tunable Diode Laser (TDL) analysers are increasingly used for fast in-situ measurements of oxygen, moisture, and hydrogen sulfide.
Their rapid response time and low maintenance requirements make them highly suitable for hydrogen-rich process environments.
Further analytical technologies include NDIR and FTIR analysers for syngas and emissions monitoring, as well as oxygen and moisture analysers for process safety and catalyst protection or UV technology for process control (jet-cut) of the final Diesel/ SAF product.
Typical measurement locations in SAF plants include feedstock treatment units, reactor inlet and outlet streams, hydrogen recycle systems, fractionation columns, flare gas lines, and final product storage.
The quality of analytical data strongly depends on the performance of the sampling system.
Even highly sophisticated analysers cannot provide reliable measurements if the sample is not transported and conditioned correctly.
In SAF plants, process streams often contain condensable hydrocarbons, water vapour, hydrogen, sulphur compounds, and particulate contamination.
The sampling system must therefore preserve the original sample composition while simultaneously protecting the analyser.
Sampling probes installed directly in the process line are designed to extract representative samples under harsh operating conditions.
Depending on the application, the probes must withstand high temperatures, elevated pressures, corrosive compounds, and hydrogen-rich atmospheres.
Modern PSG probe concepts additionally integrate high filter surface areas and optional back-purge functions to reduce maintenance intervals and improve reliability under dusty or contaminated process conditions.
Many SAF process streams require heated sample lines because condensation during transport can cause severe measurement errors.
Heated transport systems therefore maintain temperatures typically between 150 and 180 °C in order to prevent condensation and preserve sample integrity.
PSG heated line technologies also focus on minimising cold spots, improving insulation efficiency, and reducing energy consumption through optimised cable designs.
Options (model ATEX3) are available featuring a patented outer jacket design with conductive TPU to prevent electrostatic charging in hazardous-area applications with increased safety requirements.
Before entering the analyser, the sample usually passes through a conditioning system that performs pressure reduction, filtration, flow control, and temperature stabilisation.
Gas conditioning systems often include coalescing filters, knockout pots, pressure regulators, and membrane dryers.
Modern membrane drying concepts such as Nafion-based systems from PSG offer the advantage of water removal without significantly altering gas composition and can operate safely in hazardous environments.
Large SAF facilities frequently use centralised analyser shelters containing gas chromatographs, spectroscopic analysers, calibration systems, and sample conditioning equipment.
These shelters provide controlled environmental conditions and simplify maintenance and system integration.
Sustainable Aviation Fuel will remain one of the most important decarbonisation solutions for aviation in the coming decades.
As production capacities increase, the demand for reliable and highly integrated process analytics will continue to grow.
Future SAF plants will require faster analysers, improved digital connectivity, and advanced process control strategies.
Artificial intelligence and predictive maintenance concepts are expected to further improve plant efficiency, analyser availability, and energy optimisation.
The increasing use of hydrogen-based eFuels and Power-to-Liquid technologies will create additional analytical challenges related to gas purity, trace contaminants, and process safety.
At the same time, stricter environmental regulations will increase the importance of continuous emissions monitoring and online quality control.
As SAF production technologies evolve, robust sampling systems, heated sample transport, and reliable sample conditioning will remain essential for accurate and stable measurements.
Process analytics is therefore not only a supporting technology, but a key enabler for efficient, safe, and economically viable industrial decarbonisation.
[1] Geleynse, S., Brandt, K., Garcia-Perez, M., Wolcott, M., & Zhang, X. (2018). The alcohol-to-jet conversion pathway for drop-in biofuels: Techno-economic evaluation. ChemSusChem, 11(21), 3728–3741.
[2] Kalnes, T. N., Marker, T., Shonnard, D. R., & Koers, K. P. (2008). Green diesel production by hydrorefining renewable feedstocks. Biofuels Technology, 7–11
[3] Bernard, Y. (2022). Advanced technologies to produce sustainable aviation fuel (SAF). EU-India-BCE: Progress in Advanced Biofuels.
[4] Erens, J., & Reisinger, T. (2025). Probe sampling in hazardous areas under extreme conditions. CEM Middle East 2025 – Emissions & Air Quality Monitoring.
PIN 27.3 June/July 2026
Product directory
-(1).jpg)
2.jpg)
