Blending up to 20% hydrogen into fossil gas networks — as many operators hope to do — could massively increase leaks from normal household appliances such as cookers and boilers, and wipe out any climate benefit of using expensive H2 in the first place, lab tests have revealed.
Tests carried out in a UK certified lab (but not peer-reviewed) on behalf of environmental non-profit the Environmental Coalition on Standards (Ecos) found that using a 20% hydrogen blend in methane more than doubled leaks from domestic gas cookers compared to using fossil gas alone, when used under normal household conditions.
Boilers tested by UK scientists at Enertek International saw emissions increase by 44% on average.
Leakages of just 0.7% — likely in most homes on most days, the test shows —would cause additional annual greenhouse-gas emissions equivalent to 574,538 tonnes of carbon dioxide if applied to all households in the EU, and 155,755 tonnes in the UK, equivalent to the emissions from 300,000 and 84,000 fossil fuel-powered cars, respectively.
Crucially, this would mean that the climate benefit of blending 20% hydrogen into the gas — estimated at a 7% reduction in emissions due to the lower volumetric energy density of H2 compared to fossil gas — would be effectively wiped out by the leakages.
Brand new appliances bought from major UK retailers were used for the experiments, with the leakages measured by pressure losses. Tests were carried out both cold (appliances off at room temperature) and hot (appliances heated up first, then tested while off) — but Ecos has only published the more conservative results from the cold test.
The six models of cookers lost an average of 2.7 millibar of pressure per hour with the hydrogen blend, compared to 1.1 millibar per hour with methane alone, 2.4 times as fast.
And the boilers tested saw hydrogen blend leaks increase to an average of 3.8 millibar per hour, compared to 2.7 millibar per hour when using gas.
“Renewable hydrogen may likely help us decarbonise heavy industry, international shipping, and long haul flights, but with its long list of health, safety, environment, and cost problems, it has no place in our homes,” said Ecos programme manager Marco Grippa. “Why focus on this unworkable solution when there is already a clear winner? Electricity-powered heat pumps and induction cooktops are the cleaner, healthier, and safer alternative to gas in domestic settings.”
Last week, the EU passed its Hydrogen and Gas Decarbonisation Package, which obligates gas network operators to accept blends of up to 5% hydrogen, with a 75% tariff discount for hydrogen and renewable gases entering the grid. However, it has called for molecules used in this fashion to be used for industrial decarbonisation rather than domestic heating.
The UK government has largely abandoned its plans to instigate hydrogen in domestic heating, but it is still funding a controversial H2 domestic heat trial in the Scottish municipality of Fife.
And hydrogen blending will play only a limited and temporary role in the UK’s net zero transition, Westminster said last year.
Gas distributors often say that their grids can handle up to 20% hydrogen, with no safety concerns, but Spanish gas association Sedigas said last year that such a blend would require €703m of infrastructure upgrades in Spain alone.
Methane is 84-86 times more powerful a greenhouse gas than CO2 over a 20-year period, while hydrogen itself is an indirect greenhouse gas that is about 36 times more potent than carbon dioxide over 20 years.