Carbon capture, utilization, and storage (CCUS) plays an important role in meeting the European Union’s target to reduce greenhouse gas emissions by 55% by 2030 and become carbon neutral by 2050. Accurate flow metering is required throughout the carbon capture and storage (CCS) chain to meet fiscal and regulatory requirements. To establish accurate CO₂ flow metering, flow meters must be calibrated with traceability to international standards of measurement at relevant flow conditions. To ensure confidence, reliability, and comparability of calibration results, calibration facilities perform interlaboratory comparisons. However, there is currently a lack of CO₂ gas flow meter calibration facilities. The flow metering calibration facilities of VSL, NEL, INRIM, DNV, and FORCE participated in an interlaboratory comparison with CO₂ up to 400 m³/h and 31 bar(a) to compare the calibration results with several flow metering principles. At the intermediate-scale facilities of NEL, VSL, and INRIM, the difference in results between the VSL and INRIM facilities were within the facilities’ CMC values, while NEL’s facility showed a significant difference primarily due to vibrational relaxational effects of CO₂ with small critical flow Venturi nozzles. At the large-scale facilities of NEL, DNV, and FORCE, 91% of the test points passed the equivalency criteria in the range of 20 m³/h to 400 m³/h with a Coriolis meter, confirming traceability for carbon dioxide across the facilities. Overall, the interlaboratory comparison has made it possible for the CCUS industry to calibrate gaseous CO₂ flow meters with traceability to international standards.

Purity analysis of parent gases used to produce reference gas mixtures is fundamental to assure the metrological traceability of the certified gas composition, and the use of purity data in the calculation of the mixture composition should be performed in accordance with the requirements of international standards. Purity analysis can be difficult to realize since limited measurement standards are available for the determination of trace levels of gaseous compounds. The first step of purity analysis is the definition of the impurities considered critical or significant to the final composition of a mixture. In this work, we present the activity carried out for the identification and quantification of impurities of carbon dioxide and water in some ultrapure gases used for the preparation of primary certified reference gas mixtures of carbon dioxide at atmospheric amount fraction (400–800 µmol·mol⁻¹), by means of different spectroscopic techniques (Fourier Transform IR, Non-Dispersive IR and Cavity Ring-Down). Dynamic dilution was used for the generation of reference mixtures for the calibration of the analyzers by using calibrated Mass Flow Controllers. The certified reference gas mixtures produced with the tested pure gases will also be applied to characterization studies and calibration protocols for gas sensors used both for outdoor and indoor monitoring.

This work aims at presenting some activities carried out at INRiM for the development of new reference materials (RMs) of greenhouse gases to support measurements for climate change studies. Since the preindustrial era, greenhouse gases emissions due to human activities have dramatically increased, mostly due to economic and demographic growth and their concentrations in the atmosphere have grown continuously since 2011, reaching highest levels in 2019. The increase of greenhouse gases concentration in atmosphere due to anthropogenic emissions is the main cause of global warming and carbon dioxide (CO₂) is one of the main culprits for this phenomenon. In this context, the capability of discriminating between anthropogenic and natural emissions is of utmost importance. The determination of the isotopic composition of CO₂ can support the assessment of the uptake of CO₂ in the environmental compartments, i.e. atmosphere and hydrosphere, and can help to distinguish natural from anthropogenic carbon in the atmosphere. The possibility to establish metrological traceability of the measurements of CO₂ isotopic composition is a key aspect, and greatly relies on the availability of gaseous reference materials having compositions and uncertainties that are fit for purpose. In the past years, INRiM participated in the EMPIR project 16ENV06 SIRS “Metrology for stable isotope reference standards”, and is now taking part in the EMPIR project 19ENV05 STELLAR “Stable isotope metrology to enable climate action and regulation”. INRiM has experience in the preparation of gas standards by primary methods, namely gravimetry and dynamic dilution, which can be applied to the realisation of reference materials of CO₂ at known isotopic composition. The present work describes the preliminary results obtained by INRiM in the preparation of pure CO₂ RMs and at atmospheric amount fraction. Examples of uncertainty budgets and identification of the uncertainty sources are also given.

Traditionally, custody transfer measurements of natural gas have been performed using mechanical metering techniques, which rely on dynamic principles and are inherently subject to mechanical wear. Only recently have static measurement technologies convincingly emerged on the market, including capillary-type thermal mass flowmeters (CTTMF). In legal metrology, it is crucial to define the maximum permissible errors both for new meters and during periodic verification (in-service accuracy). While the performance degradation over time is well established for dynamic techniques, reliable empirical data proving the temporal stability of static meters remain scarce due to their relatively recent market introduction. In this article, the authors present an extended statistical investigation conducted on a large and homogeneous sample of tested CTTMF meters. This work significantly expands the observed field service period up to 12 years, building upon a previous 8 year study previously presented at the XXIV IMEKO World Congress (Spazzini et al 2025 Measurement 38 101536). It was found that an extremely high percentage of the analyzed meters not only respect the in-service accuracy limits (over 99%), but even remain within the limits of first verification (over 80%).