Proponents of blue hydrogen — derived from natural gas with carbon capture and storage — say it is a vital tool in reducing greenhouse gas emissions as vast amounts can be produced more rapidly and cheaply than green H2 from renewable energy.

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Critics say it is potentially worse for the planet than burning natural gas, that it is not a “low-carbon” solution and that its use could lock in fossil fuels for decades to come.

Last week, the UK government unveiled plans to rapidly scale up domestic production of “low-carbon hydrogen” to 10GW by 2030, with 50% apparently coming from blue H2.

At the same time, it unveiled a definition of “low-carbon” — 20 grams of CO2 equivalent (CO2e) per megajoule of hydrogen, which translates to 2.4kg of CO2e per kilogram of H2.

This means that total emissions from blue hydrogen projects — including upstream methane emissions, carbon dioxide that cannot be captured, leaks from the transportation and storage of the captured CO2, and emissions from electricity used — would need to fall under this upper limit to move forward and be eligible for government subsidies.

So how difficult will it be for blue hydrogen projects meet this criteria?

Independent experts contacted by Recharge say it will be very challenging, while Equinor — one of the world leaders in future blue hydrogen projects, says that the threshold is “strict but feasible”.

The handful of blue hydrogen projects built to date have a carbon capture rate of less than 50%, and steam methane reformation (SMR) — the standard method of hydrogen production today — is generally considered to be able to capture 80-90% of CO2 emissions from the process. To achieve higher capture rates, a more expensive process known as autothermal reforming (ATR) — which requires added heat — may be required, achieving up to 99% capture due to a more concentrated stream of CO2 in its flue gases.

An Equinor spokesperson tells Recharge that British facilities “will need at least 90% carbon capture if using UK gas and preferably 95% to have a workable margin”.

“We see that modern blue hydrogen plants, using SMR, ATR or combinations thereof, can be designed to capture more than 95% of the carbon entering the plant and we specify this rate for our projects,” the spokesperson says.

“As for the implications for gas sourcing, anything approaching 1% emissions in production and transport will struggle to meet the threshold.”

In a data annex to the UK government’s new Low Carbon Hydrogen Standard (LCHS) document, the UK government put total upstream emissions from natural gas drawn from the UK gas network as 4.54gCO2e/MJ.

According to calculations provided to Recharge, that translates as a methane emissions rate of 0.8% — if not taking into account upstream CO2 emissions, such as burning natural gas to fuel compressors or to produce heat and power on gas platforms (and when giving the non-methane parts of the natural gas the same energy content as methane).

Add these upstream emissions and any leaks from the CCS process, and this will reach an equivalent of 1% methane emissions, says Michael Barnard, chief strategist at Canadian consultancy firm TFIE.

Equinor points out that methane emissions vary from company to company, adding that itself and several of the oil supermajors, including BP, Shell, Exxon Mobil, TotalEnergies, and Chevron, have pledged to reduce methane emissions to 0.2% by 2025 as part of the Oil and Gas Climate Initiative.

The UK has made life a little easier for blue hydrogen producers by choosing to use a global warming potential (GWP) of 100 years in its calculations. The GWP100 for methane is 29.8, according to the latest IPCC report — meaning it is 29.8 times more potent a greenhouse gas than CO2. By contrast, if a 20-year GWP was used, that figure would be 82.5 (according to the new IPCC report) — making it much harder for blue hydrogen projects to meet the UK’s LCHS.

The government has been fiercely criticised for using the 100-year GWP, seeing as it has pledged to reach net-zero emissions by 2050, in just 28 years’ time.

But the Department for Business, Energy and Industrial Strategy tells Recharge that “the methodology is in line with IPCC guidance and UNFCCCreporting requirements” and that “our national and international emissions targets are set in legislation using 100 year Global Warming Potentials”.

Equinor says that even if the GWP20 figures were used for methane, “Equinor’s hydrogen will be well within the threshold of 20gCO2e/MJ due to our very low upstream emissions”.

The spokesperson adds: “Given the 4.54 gCO2e/MJ for UK natural gas indicated in the LCHS, and assuming 95% capture and an efficient process, blue hydrogen plants using UK supplied gas should meet the threshold.”

However, others are not convinced.

Mark Thomson, executive director at Australian emissions consultancy Carbon Transition Pathways, tells Recharge that meeting the UK LCHS threshold would require 0.1% methane emissions and 96% carbon capture — which he describes as “barely” possible and not remotely likely. Thomson also points out that the UK is a net importer of fossil gas, relying on LNG imports, which have a far higher greenhouse gas footprint than domestic sources.

Barnard offers a slightly more favourable opinion, telling Recharge that “a small number of very well managed natural gas providers that have minimal upstream methane leakage” could meet the low-carbon threshold.

But he adds: “What is possible is very far from what is probable and provably done. What is possible is also more expensive and hence even less economic.”

According to analysts BloombergNEF, Rystad Energy and others, sky-high natural-gas prices in Europe mean that green hydrogen is currently a far cheaper option than blue H2, and given the continent’s rush away from Russian gas, it does not seem that they will fall back to historic levels any time soon.

Equinor told Recharge last week: “It is evident that the current gas prices would have an effect on the economy [of] blue hydrogen projects. However, we do expect that gas prices will eventually reach more normal levels.”