As the world approaches a state of climate crisis, low-carbon fuels (LCFs) are an essential part of the sustainable energy transition, as many forms of transportation and industry cannot easily be switched to pure electricity. From hydrogen gas to biomethanol, LCFs are often touted as ‘green’ fuels as they burn cleaner or have a lower carbon footprint compared to conventional fossil fuels.
However, when is a green fuel truly green, and when is it simply being greenwashed? Fuu Ming Kai, a Principal Scientist at the A*STAR National Metrology Centre (A*STAR NMC), gave the example that a unit of hydrogen fuel might be produced from sustainable solar electricity and water, or from methane reforming—a fossil fuel-based method. While both methods produce very different levels of carbon emissions, it can be difficult to verify which method was involved.
“Production methods can be misrepresented, and without physical verification, documents can be manipulated to present conventional fuels as LCFs,” said Kai.
In a recent poster presented at the Bureau International des Poids et Mesures (BIPM) 150th Anniversary Scientific Conference, Kai and A*STAR NMC colleagues including Senior Research Engineer Yuxi Cui and Research Engineer Lemuel Joel Kuehsamy explored a potential solution to LCF greenwashing: isotopic fingerprinting.
“Think of isotopic fingerprinting as a chemical barcode,” said Kai. “Within a sample of fuel, the mix of elements present—carbon, hydrogen and so on—come in slightly different forms called isotopes, which can be found in varying proportions, depending on how the fuel was produced. By measuring these tiny differences, we can identify the isotopic signature they create and use it as physical evidence of a fuel’s low-carbon origins.”
Isotopic fingerprinting also offers a means to track ambiguous sources of greenhouse gas (GHG) emissions. Kai highlighted how next-generation laser-based measurement systems such as cavity ring-down spectroscopy can be bundled into highly sensitive yet compact devices for on-site GHG monitoring, doing away with the need for lab-based mass spectrometry.
However, these tools also need more frequent calibration, robust reference materials and standardised protocols to maintain trust and comparability. Kai indicated the need for isotope databases with details of feedstock origins, production processes and environmental conditions, as LCFs can contain a diverse array of organic compounds and impurities.
“There’s also a lack of traceable, stable isotopic reference standards, which would ideally act as trusted benchmarks to ensure that measurements are accurate and comparable across labs and countries,” said Kai.
To meet this need, Kai noted that A*STAR NMC is actively involved in developing isotopic measurement methods and reference materials for biomethane, biomethanol and e-methanol. In its role as an International Atomic Energy Agency Regional Expert Centre, the institute is also fostering knowledge exchange, harmonising measurement methodologies, and building a robust network of scientific expertise across borders.
“Our efforts support authorities and industries such as aviation and shipping, where verified LCF authenticity is critical for regulatory compliance and climate goals,” said Kai.
The A*STAR researchers contributing to this research are from the A*STAR National Metrology Centre (A*STAR NMC).
