Blue hydrogen installations using fossil gas and carbon capture and storage (CCS) technology could prove hugely beneficial to the planet — but they could also be a disaster for emissions reductions efforts if their climate impacts are assessed inaccurately, scientists from the US-based non-profit Environmental Defense Fund (EDF) have warned.

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In fact, blue hydrogen projects could reduce global warming effects by 70% compared to equivalent unabated fossil-fuel use in the near-term, if methane emissions are low, EDF said in a study published in the journal Environmental Science & Technology today (Wednesday).

If, on the other hand, methane emissions are high, blue H2 production and use could actually increase short-term global warming effects by 50% compared to fossil fuels.

This disparity in benefits is likely to be exacerbated by flawed emissions accounting methodology, the EDF went on to say, which could cause blue hydrogen projects to actually damage the climate despite being assessed as having a positive impact.

And the emissions benefits of renewable hydrogen projects are also likely to be overestimated if lifecycle emissions are not correctly analysed, the non-governmental organisation (NGO) added.

As such, EDF is calling for a massive overhaul of the way the climate impacts of blue and green hydrogen projects are judged, singling out the Hydrogen Council’s widely-referenced hydrogen lifecycle analysis (LCA) from 2021 for a revamp in today’s paper.

“It’s important to get the emissions accounting right, both to accurately assess climate impacts of hydrogen systems and to identify opportunities to reduce them,” said EDF climate scientist and lead author Tianyi Sun. “When we consider all climate warming emissions and their impacts over the near- and long-term, our analysis shows that hydrogen deployment can have far greater impacts than expected.”

Scientists from EDF and the University of Arizona re-analysed the Hydrogen Council LCA along what the paper’s authors say are four key fault lines: underestimation of likely hydrogen emissions, inconsistent estimates of real reported methane emissions, the availability of renewable electricity, and the metrics used to assess global warming potential.

Methane emissions in particular, which have a global warming potential (GWP) 28 higher than carbon dioxide over 100 years, have been routinely underestimated, accounting for the disparity between the different potential climate impacts of blue H2 projects, the paper asserts.

“While methane emissions are often included in hydrogen technology climate impact assessments, the emissions rates are often not consistent with those actually observed across a diversity of facilities and supply chains,” it reads. “Direct measurements that have been made over the last decade suggest that there are large regional- and basin-level variations in methane emission intensities, from less than 62.1% to more than 3%.”

It adds: “However, the assumption of low methane leakage is common, while some studies exclusively assume high methane leakage.”

Noting that there is little real-world reporting of hydrogen leaks, the report’s authors also expressed concern that leakage of the tiny H2 molecule is likely to be similarly underestimated, while it also took issue with the global community’s tendency to measure global warming impacts over 100 years, rather than near-term impacts.

Methane is even more potent over 20 years, believed to have a GWP of up to 87 times that of CO2 during that time frame.

The authors applied what they described as “plausible” H2 and methane emissions calculations to the Hydrogen Council’s analysis, as well as taking into account the varying availability of renewable energy and a range of different timeframes for GWP.

As well as finding that the climate impact of blue hydrogen projects is significantly affected both by the time frame used (20 years, as opposed to 100 years) and more robust emissions assumptions, the study also found that the emissions reductions from green hydrogen production could be 25% less than previously assumed, due to H2 leaks.

The authors also re-analysed carbon capture rates, which the Hydrogen Council assumed to be 98% — far higher than has been commercially achieved, EDF argued.

In this analysis, carbon capture rates of 60% pushed down the short-term blue H2 project climate benefits (compared to 98%) by 15-50% in the near-term, and 20-60% in the long-term.

The study also confirmed findings from other papers, which have long asserted that renewable energy scarcity and a lack of “additionality” rules (mandating that green hydrogen installations use only new renewables capacity) eliminates intended climate benefits, and pushes up emissions at the grid level. This happens when clean electricity normally consumed by the grid is instead diverted to electrolysers, requiring fossil-fuel power stations to be fired up to replace those lost electrons.

“The findings of this study are pressing: hydrogen made from fossil fuels with CCS has the potential to release a cocktail of emissions with warming impacts up to 50% worse than traditional fossil fuels,” said Professor David Cebon, professor of mechanical engineering at Cambridge University and co-founder of independent expert group the Hydrogen Science Coalition. “Policymakers evaluating such projects must quantify these emissions carefully and thoroughly.

“By rigorously accounting for hydrogen and methane leaks across the hydrogen lifecycle, this paper shows the tightrope that hydrogen must walk to progress the energy transition rather than derail it.

“Any government considering hydrogen in their net-zero strategy needs to read this paper.”