Natural gas is a fossil fuel, an energy source that formed deep beneath the earth's surface.
Natural gas contains methane and smaller amounts of hydrocarbons (mainly C2- C6) which act as a fuel source, as well as non-hydrocarbon gases, such as carbon dioxide and water vapor. The composition varies depending on its origin, but when burned all emit gases into the atmosphere that contribute to global warming. As a result, natural gas usage is expected to decline in Europe and should be replaced with renewable or low carbon sources, but will inevitably still play a role during the energy transition.
A number of metrological challenges need to be resolved. For example, it is important to verify the performance of custody transfer meters, which are used to measure the quantity of gas for custody transfer. The energetic value (calorific value) is usually determined by measuring the gas composition using gas chromatography and applying a theoretical model that accounts for the particular composition. Alternatively, it's possible to measure the combustion energy of the natural gas using a calorimeter.
Specific measurement challenges of natural gas are related to flow, gas composition, calorimetry and have been dealt with in the following joint research projects within EURAMET's European Metrology Research Programmes, EMRP and EMPIR.
Examples of relevant standards include:
- ISO6974 series: Determination of composition and associated uncertainty by gas chromatography
- ISO6976: Natural gas - Calculation of calorific values, density, relative density and Wobbe indices from composition
- ISO10715: Natural gas - Sampling guidelines
- ISO12213: Natural gas - Calculation of compression factor - Part 3: Calculation using physical properties