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Swansea study finds 30% of the UK’s natural gas could be replaced by hydrogen without major changes

30% of the natural gas fueling UK homes and businesses could be replaced by hydrogen without requiring any changes to the nation’s boilers and ovens, a study by Swansea University researchers has shown. Over time the move could cut UK carbon dioxide emissions by up to 18%. The open-access study is published in the RSC journal Sustainable Energy & Fuels.

The difference between the two percentages—30% hydrogen enrichment and a potential 18% drop in carbon emissions—arises from the fact that hydrogen-enrichment lowers the calorific content of the fuel, necessitating a higher volume of gas for a given energy output.

Domestic gas usage accounts for 9% of UK emissions. In an effort to reduce annual carbon emissions, there is presently a concerted effort from researchers worldwide to offset the usage of natural gas. Enriching natural gas with hydrogen (HENG) is one option. Experiments have shown that modern-day gas appliances work safely and reliably with hydrogen-enriched natural gas as the fuel. It is already used in parts of Germany and the Netherlands. A £600-million (US$805-million) government-backed trial is taking place in the UK this year.

Natural gas naturally contains a small quantity of hydrogen, although current UK legislation restricts the allowed proportion to 0.1%. The question the Swansea team investigated was how far they could increase the percentage of hydrogen in natural gas, before it became unsuitable as a fuel, for example because the flames became unstable.

European trials have already been conducted to investigate the practical implementation of hydrogen-enriched natural gas (HENG) within a mains gas supply. In this work, the limitations of such a strategy are evaluated based on a novel meta-analysis of experimental studies within the literature, with a focus on the constraints imposed by the phenomena of flash-back and blow-off.

Through consideration of the Wobbe Index, we discuss the relationship between molar hydrogen percentage and annual carbon dioxide output, as well as the predicted effect of hydrogen-enrichment on fuel costs. It is further shown that in addition to suppressing both blow-off and yellow-tipping, hydrogen-enrichment of natural gas does not significantly increase the risk of flash-back on ignition for realistic burner setups, while flash-back at extinction is avoided for circular port diameters of less than 3.5 mm unless the proportion of hydrogen exceeds 34.7 mol%. It is thus proposed that up to 30 mol% of the natural gas supply may be replaced in the UK with guaranteed safety and reliability for the domestic end-user, without any modification of the appliance infrastructure.

—Jones et al.

The team—Dr. Charles Dunnill and Dr. Daniel Jones at the University’s Energy Safety Research Institute (ESRI)—found:

  • An enrichment of around 30% is possible, when various instability phenomena are taken into account.

  • Higher percentages make the fuel incompatible with domestic appliances, due to hydrogen’s relatively low energy content, its low density, and a high burning velocity.

  • 30% enrichment by hydrogen nevertheless equates to a potential reduction of up to 18% in domestic carbon dioxide emissions.

The research was supported by the Welsh Government Sêr Cymru Program, FLEXIS, which is partially funded by the European Regional Development Fund, and the King Saud University as well as by the Welsh Government through the Sêr Cymru Chair for Low Carbon Energy and Environment. Co-author is Waheed Al-Masry an assistant professor in the Department of Chemical Engineering at King Saud University, Riyadh, Saudi Arabia.


  • Daniel R. Jones, Waheed A. Al-Masry and Charles W. Dunnill (2018) “Hydrogen-enriched natural gas as a domestic fuel: an analysis based on flash-back and blow-off limits for domestic natural gas appliances within the UK” Sustainable Energy & Fuels 2, 710-723 doi: 10.1039/C7SE00598A



OK, nice to find a use for H2.
I have a few questions and observations:
a: What about hydrogen embrittlement of the gas pipes, they were designed for methane, not H2.
b: It is a pity you have to use H2 to replace the cleanest fossil fuel, rather than coal or oil, which contain much more carbon, sulphur etc.
c: If they started at 5%, then 10 etc, they could find out what will really happen, there may be some gotcha's in there.

Thomas Lankester

Taking those points:
a) a lot of the network is being already converted to polypropylene pipes anyway since 2002 through the Iron Mains Replacement Programme (IMRP)
b) no point replacing (thermal) coal with hydrogen as the UK is phasing its use out anyway. Similarly for road transport with EVs.
Servicing the fossil fuel needs of 23 million gas customers however is more of a stumbling block.
c) the 5-10% tests have already been done through ITM's trials in Germany and the on-going trials of the Leeds Gateway H21 project (https://www.businessgreen.com/bg/news/3022389/gbp9m-boost-for-pioneering-hydrogen-heating-project) are working on 100% hydrogen.


The news here is the UK is moving ahead with plans to convert fossil fuel over to clean energy and is working on many fronts; unlike the U.S. that can't get past their big election mistake who is in the White House.


Someone has done 10% without problems. You could do like Audi and Energy Wind, take water treatment CO2 to make methane.


And the potential of 100% CO2 reduction from powering the home uses with nuclear electricity gets ignored once again.

MJ Grieve / AHEAD Energy 501c3

This seems like a poor approach. Changing to heat pumps and electrification of heating brings much more flexibility. Retooling to use carbon free fuels like hydrogen and ammonia can cover most of the cases where supplemental fuel is needed. Using these carbon free fuels in fuel cells, as a high efficiency CHP approach, is about twice as efficient as burning these fuels for heat...


The study refers to domestic gas appliances but there are industrial applications that are well suited to efficient efficient combustion or other. These could include turbine generators and domestic or small CHP.
The gas infrastructure and it's capacity for storage has benefits as both backup or alternative energy source means overall reliability is enhanced.
The system infrastructure can also absorb excess renewable electricity even if not at the highest efficiency,
If renewable H becomes widespread eventually , and the infrastructure is upgraded it would seem possible or even necessary as a complimentary piece of the clean energy puzzle.

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