Debunking The Myth: Hydrogen Isn’t Really A Clean Burning Fuel – CleanTechnica

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Hydrogen is often celebrated as the fuel of the future, heralded as a perfect solution that emits no carbon dioxide (CO₂) when burned or utilized in fuel cells. Yet, while technically correct — hydrogen itself emits no carbon dioxide upon combustion — the framing of hydrogen as a fully ‘clean’ fuel conveniently omits significant and alarming environmental concerns.

This is a companion article to the Cranky Stepdad vs Hydrogen for Energy material. In a similar manner to John Cook’s Skeptical Science, the intent is a rapid and catchy debunk, a second level of detail in the Companion to Cranky Stepdad vs Hydrogen for Energy, and then a fuller article as the third level of detail.

Hydrogen burns clean, but it’s like sweeping the dirt under the rug — ignores NOₓ emissions & leaks.

The claim frequently championed by advocates — that hydrogen combustion is emission-free — intentionally or unintentionally overlooks two critical issues: the indirect greenhouse gas effects of hydrogen leakage, and the harmful nitrogen oxides (NOₓ) produced when hydrogen is combusted. These problems fundamentally challenge the popular image of hydrogen as a flawless energy carrier.

Hydrogen’s indirect greenhouse effects have garnered attention in recent years, particularly given the urgent global focus on methane reduction. The nuanced truth is that hydrogen acts as an indirect greenhouse gas by prolonging the atmospheric lifetime of methane, a far more potent greenhouse gas than CO₂ in the short term (Ocko & Hamburg, 2022). Indeed, leaked hydrogen in the atmosphere interacts chemically, reducing the availability of hydroxyl radicals (OH) that would otherwise break down methane. This significantly amplifies the global warming potential of methane and, in turn, exacerbates climate change (Derwent et al., 2020).

While hydrogen’s direct Global Warming Potential (GWP) is conventionally stated as zero, its indirect Global Warming Potential (GWP100) is now acknowledged to be approximately 12, and its GWP over a 20-year timeframe (GWP20) is estimated at 37 (Ocko & Hamburg, 2022). DEFRA’s 2022 study, assessing atmospheric impacts, suggests that hydrogen’s indirect global warming effects have been drastically underestimated.

This is quite normal. According to Boucher et al. (2009), methane’s Global Warming Potential (GWP) at a 100-year horizon includes both direct and several indirect effects. Methane’s direct GWP100 is approximately 18.6, accompanied by indirect contributions of 4.3 from ozone (O₃) formation, 2.6 from stratospheric water vapor (H₂O), and a minor impact of 2.2–3.6 due to CO₂ produced by oxidation of methane from fossil sources. Additionally, methane from anthropogenic biogenic sources has a slightly negative indirect CO₂-induced impact (−4.1 to 0.0), partially offsetting its overall warming effect.

When considered in practical terms, the issue becomes even more severe. For instance, standard leakage rates across hydrogen value chains — from production, storage, transport, to end-use — can range between 5% and 10%, depending on the application and the robustness of infrastructure (Derwent et al., 2020). Even modest leaks can dramatically undermine hydrogen’s supposed climate advantages, leading to outcomes potentially worse than burning natural gas directly.

Adding to hydrogen’s indirect climate impacts, its combustion — far from ‘clean’ — emits significant nitrogen oxides (NOₓ). These emissions are well-established environmental and public health hazards, contributing directly to ground-level ozone formation, smog, and respiratory diseases, which disproportionately affect vulnerable populations (Zhang et al., 2019). Contrary to the claims of ‘clean combustion,’ NOₓ emissions from hydrogen combustion often rival, and in certain cases exceed, emissions from fossil fuel combustion in similar scenarios (Ocko & Hamburg, 2022).

The complexity and cost required to manage NOₓ emissions from hydrogen combustion further compound the issue. Achieving low NOₓ emissions necessitates precise combustion control or expensive catalytic systems, significantly increasing operational costs and complicating the widespread adoption of hydrogen as a combustion fuel (Zhang, Li, & Zhang, 2019).

Despite clear scientific evidence highlighting these indirect greenhouse gas effects, the hydrogen industry and many proponents still market hydrogen as a universally clean solution. This approach dangerously oversimplifies the narrative, providing policymakers and investors with a distorted understanding of hydrogen’s environmental implications. A study published in Energy & Fuels demonstrates how hydrogen blends in domestic boilers substantially increase NOₓ emissions compared to pure natural gas combustion, directly challenging the popular narrative of hydrogen’s purity (Zhang, Li, & Zhang, 2019).

From an ecological perspective, the International Council on Clean Transportation (ICCT) emphasized in a 2022 analysis that wide-scale hydrogen infrastructure could risk amplifying rather than mitigating climate change, given realistic leakage rates of 5% to 10% in common energy applications. This issue demands robust regulation, leak monitoring systems, and stringent operational standards, none of which are adequately highlighted by hydrogen proponents who simplistically claim “zero emissions” (International Council on Clean Transportation [ICCT], 2022).

Perhaps most troubling is how infrequently hydrogen’s indirect climate impacts surface in mainstream policy debates. Research by Derwent et al. (2020) emphasizes that hydrogen’s atmospheric lifetime and interaction with methane mean that leakage risks must be explicitly included in any credible climate benefit assessment. Despite growing recognition in academic circles, policy frameworks and subsidy programs largely omit these factors, risking misguided investment that could lock in unintended environmental consequences.

The UK government’s hydrogen strategy, for instance, optimistically outlines hydrogen’s role in achieving net-zero without fully accounting for hydrogen’s indirect greenhouse gas effects. The DEFRA (2022) report explicitly calls for increased scrutiny on hydrogen leak mitigation, noting that current regulatory frameworks inadequately address hydrogen leakage risks. Such gaps in policy reveal either an alarming ignorance or a willful disregard of essential climate science, especially when billions of dollars in public funding and incentives are at stake.

An effective approach to deploying hydrogen responsibly requires transparent acknowledgment and rigorous regulation of both leakage and NOₓ emissions. For example, comprehensive leak detection and stringent emissions standards could mitigate the indirect climate impact considerably, though not eliminate it entirely. Without these measures, advocating for hydrogen as a sustainable fuel risks exacerbating rather than mitigating global climate change.

Comparatively, renewable electricity solutions such as solar and wind, combined with electrification, bypass these indirect greenhouse gas concerns entirely. Electrification directly removes the issues of hydrogen leakage and NOₓ emissions at the point of use, providing a truly emissions-free pathway. Moreover, battery electric technologies consistently demonstrate superior energy efficiency, fewer environmental externalities, and greater reliability compared to hydrogen-based alternatives, particularly in transportation and heating applications.

Ultimately, the characterization of hydrogen as simply “zero emissions” is misleading. Its indirect greenhouse gas impacts, substantial NOₓ emissions, and persistent leakage issues necessitate a cautious, realistic approach favoring genuinely emissions-free solutions whenever possible. Transparency and rigorous oversight are essential — not optional — for genuine climate progress.

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References:

International Council on Clean Transportation (ICCT). (2022). Assessing the climate impacts of hydrogen leakage. Retrieved from https://theicct.org/publication/hydrogen-leakage-climate-impacts-2022/

Boucher, O., Friedlingstein, P., Collins, B., & Shine, K. (2009). The indirect global warming potential and global temperature change potential due to methane oxidation. Environmental Research Letters, 4(4), 044007.

DEFRA. (2022). Atmospheric Impacts of Hydrogen: UK Research Programme Summary.

Derwent, R. G., Simmonds, P. G., Manning, A. J., & Spain, T. G. (2020). Global environmental impacts of hydrogen leakage. International Journal of Hydrogen Energy, 45(7), 3875–3893.

Ocko, I. B., & Hamburg, S. P. (2022). Climate consequences of hydrogen emissions. Atmospheric Chemistry and Physics, 22(12), 9349–9368.

Zhang, Y., Li, J., & Zhang, S. (2019). NOₓ emission characteristics of hydrogen/methane blends in domestic gas boilers. Energy & Fuels, 33(11), 11202–11209.