Liquefied natural gas & Liquefied biogas

Liquefied natural gas (LNG) is predominantly methane (CH4), with some mixture of ethane, (C2H6) that has been cooled down (ca. -162 °C) to liquid form.

It takes up about 1/600th the volume of natural gas in the gaseous state. LNG is a strategic, and in the case of long distances, a more economical alternative for pipeline gas. It is also used to transport natural gas from and to locations where no pipeline infrastructure exists. It is also a more sustainable alternative as fuel in maritime transport.


Liquefied biogas (LBG) – also known as liquefied biomethane and bio-LNG – is a fossil-free and 100% renewable fuel that can reduce CO2 emissions over its life cycle by up to 90% compared with conventional fuels.

As a fuel, LBG is interchangeable with LNG, as they both mainly consist of methane (CH4).

Nevertheless, as LNG is a cryogenic liquid, several issues arise in measuring at low temperature flow, humidity and composition. In particular, robust and reliable sampling remains a challenge as it requires quantitative vaporization.

Specific measurement challenges for LNG and LBG are related to flow, composition, CRM, sampling, physical properties 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:

  • EN16723-1
  • EN16723-2
  • ISO21903:2020: Refrigerated hydrocarbon fluids - Dynamic measurement - Requirements and guidelines for the calibration and installation of flowmeters used for liquefied natural gas (LNG) and other refrigerated hydrocarbon fluids