Implementation of a validation protocol to ensure a reliable assessment of the biomethane quality: practical demonstration of its fit-for-purpose using ISO 2620:2024 to comply with the requirements set in the EN 16723 standards

Biomethane is expected to be important in meeting Europe's greenhouse gas reduction target. The composition of biomethane varies, therefore, depending on the feedstock and process parameters. The European standards EN 16723 specify requirements for injecting biomethane into natural gas networks and its use as vehicle fuel. Ensuring that biomethane composition complies with the requirements set in the standards requires rigorous quality control processes and validated analytical methods. Method validation for parties lacking practical experience or training can be a complex process involving numerous steps and requires adequate guidelines, which were lacking for biomethane. The BiometCAP project has, therefore, developed a standardized protocol for evaluating gas analyzers in biomethane applications with detailed procedures for assessing instrument performance and ensuring accurate and reliable measurements. This article describes how to use the validation protocol with practical applications for evaluating the limit of detection and limit of quantification, the working range and linearity, the precision, the bias and finally to calculate the measurement uncertainties using the analytical method described in ISO 2620:2024 as an example. This method based on TD-CG/MS-FID can therefore be considered fit-for-purpose, providing reliable, precise and sensitive measurements for the analysis of VOCs as demonstrated for 3-carene, dichloromethane and hexamethyldisiloxane. Finally, the article also summarizes the measurement uncertainties obtained during an extensive evaluation exercise organized between seven NMIs across Europe. For any future validation work, measurement uncertainties of 1 to 10% relative for any regulated compounds can be used as reference.