Gas Quality Working Group

What is the Gas Quality Working Group?

A group of experts brought together to facilitate the production of a new IGEM standard specifying the quality of gas that is allowed to be injected into the UK’s gas transmission and distribution network.

Working Group Documents

All of the documents produced by this working group are available here.

Who’s involved? 

Changes in gas quality have the potential to impact the whole of the supply chain and the makeup of the gas quality working group aims to reflect this. The individuals involved represent: the Health and Safety Executive (HSE), National Grid Transmission, the Gas Distribution Networks (GDNs) Cadent, SGN, Northern Gas Networks and Wales & West Utilities, Energy UK, the Industrial and Commercial Energy Association (ICOM) and boiler manufactures. In addition the working group has input from a number of specialist consultants including DNV GL and Kiwa.

Why is this standard required?

The UK benefits from a long established gas network with a proven history of delivering natural gas safely, affordably and reliably to millions of customers each year. However, if we are to meet the target of net zero gas emissions by 2050, then it is essential that we consider how we will continue to supply heat, power and light whilst reducing our impact on the environment.

In response to the emissions challenge the gas industry has embarked on a number of innovative projects designed to decarbonise the gas network and reduce the carbon footprint associated with gas usage. Many of these projects explore the potential of alternative, low carbon gases such as biomethane, bioSNG and hydrogen. 

Some low carbon gases are already being added into the network alongside natural gas. However, in order to maximise the full potential of alternative gases a change is required to the specification of gas that is permitted to be injected into the network.

The current specification for UK gas quality sits within the Gas Safety (Management) Regulations 1996 and was developed based upon the characteristics of North Sea natural gas. As an increasing percentage of the natural gas used in the UK is imported and we seek to increase the use of low carbon alternatives to natural gas, there is a requirement to change the specification of gas that is permitted for use under the GS(M)R and to align the UK standard with the European standard.

How is gas quality measured?

Gas quality is measured by the Wobbe index which is used to compare the combustion energy output of different composition fuel gases in an appliance (fire, cooker etc.). If two fuels have identical Wobbe indices then for given pressure and valve settings the energy output will be identical.

The Wobbe index is a critical factor in minimising the impact of substituting natural gas with low carbon alternatives. Each of the various types of low carbon gas measures differently against the Wobbe index and some do not fit within the parameters set out within GS(M)R.  For example, the Wobbe index requires the addition of propane to some upgraded biomethane products.

The IGEM gas quality standard will set a new Wobbe index range for gases used within the UK network. Initially it will extend the upper range however it will seek to widen the lower range at a later date.


The publication of an IGEM standard covering gas quality. This work is a pre-curser to a request to change the specification of gas quality that sits within GS(M)R in order to enable an increase in the use of low carbon gases alongside natural gas.

Related projects

Opening up the gas market

The Gas Quality Working Group was brought together in response to SGN’s innovation project entitled Opening Up the Gas Market. The project was designed to test different compositions of gas throughout SGN’s network in Oban, Scotland to see how it performed and demonstrate its suitability for the GB market.

The variations of gas tested are already used in Europe but require further processing to meet our national standard. The trial at Oben sought to demonstrate that the national standard could be revised to open up the gas market and lower prices for customers.

Exploring the impact of varying gas quality on industrial and commercial users

As part of the work being undertaken by the Gas Quality Working Group energy consultants DNV GL were tasked with assessing the impact of varying gas quality on industrial and commercial users.

The project explored the effect of a wider Wobbe index that permits use of blended hydrogen mixtures containing up to 20 mol%, by researching and reviewing measures that have been put in place around the world to ensure the safe and efficient combustion of wider specification gases. The rate of change of the Wobbe index was also considered.

Industrial and commercial equipment greater than 1 MW in size was examined along with instrumentation that measures or may be affected by gas quality. The project primarily considered a range of Wobbe index from 45.67 to 53.25 MJ/m3 compared with the existing GS(M)R range of 47.20 to 51.41 MJ/m3. 

The resulting report produced by DNV GL on behalf of the Gas Quality Working Group is available to download below. 

Industry consultation

In January 2018, a group of stakeholders from the commercial and industrial sector were invited to IGEM House for the first stakeholder workshop. Attendees were provided with an overview of the work being carried out by the Gas Quality Working Group including the rationale for the proposed changes to GS(M)R. The workshop also provided an opportunity to gather information about the quality of gas currently supplied to the GB network.

The presentations given are available to download below along with a summary of the workshop outputs.