H2 set-up in WILIAM, hydrogen economy scenarios, and results

The model now covers the entire hydrogen value chain, including production, transport, storage, and end uses in industry and transport. It also considers hydrogen emissions and leakages, as well as their impact on air quality and the environment.

Another key activity focused on developing future scenarios up to 2100. Alongside a Reference Scenario based on current trends, four Green Growth scenarios were created, incorporating higher deployment of renewable energy, electrification, energy efficiency measures, and other decarbonisation strategies.

By combining different levels of hydrogen adoption with various assumptions on hydrogen emissions and leakages, the team developed 20 scenarios. These scenarios provide a robust basis for evaluating the potential role of hydrogen in supporting the transition to a more sustainable and low-carbon future.

The model was upgraded to represent the entire hydrogen value chain, including production, transport, storage, and end-use applications. This ensures that hydrogen deployment is analysed as part of the broader energy system rather than as a standalone technology.

To explore possible futures, the project developed a set of scenarios based on different assumptions about economic growth, clean energy adoption, and hydrogen use:

• A Reference Scenario, reflecting current trends.
• A Green Growth scenario without hydrogen, focused on renewable energy, electrification, and energy efficiency.
• Three hydrogen deployment scenarios (low, medium, and high), representing increasing levels of hydrogen use across sectors such as industry, transport, steel production, and synthetic fuels.

Each hydrogen scenario was combined with different assumptions on hydrogen emissions and leakages, creating a wide range of possible future pathways.

The team also harmonised emissions data and validated the model against historical climate and air-quality records. This made it possible to assess both the benefits and potential trade-offs of a future hydrogen economy and to provide reliable inputs for advanced climate and atmospheric models.

It is important to note that these results are preliminary and continue to be refined to improve the accuracy of the climate and atmospheric models used in the project.

One of the key achievements is that WILIAM can now simulate a wide range of hydrogen adoption pathways and assess their impacts on energy systems, the economy, land use, materials, and emissions. The model generated 20 scenarios, providing a solid basis for further climate and air-quality analyses.

The results show that the Green Growth scenarios consistently lead to lower greenhouse-gas emissions and air pollution than the Reference Scenario. These improvements are mainly driven by greater use of renewable energy, electrification, energy efficiency, and reduced reliance on fossil fuels.

The impact of hydrogen is more complex. In the short to medium term, higher hydrogen deployment can sometimes lead to slightly higher emissions because additional energy and infrastructure are needed to produce, transport, and store hydrogen. However, over time, hydrogen helps reduce emissions by replacing fossil fuels in sectors that are difficult to decarbonise, such as heavy industry and freight transport.

Air pollutant emissions follow a similar trend, with the largest reductions occurring in the transport sector due to increasing electrification and the adoption of cleaner fuels.

The analysis also highlights the importance of hydrogen leakage management. As hydrogen use grows, leakages during production, transport, and storage become a more significant source of emissions, making effective control measures essential.

Finally, hydrogen demand increases in all deployment scenarios, especially after 2050. While low-deployment scenarios mainly focus on existing industrial uses, medium- and high-deployment pathways expand hydrogen use to sectors such as steel production, high-temperature industrial processes, freight transport, and synthetic fuel production. These hard-to-electrify sectors become the main drivers of future hydrogen demand.

The results indicate that implementing H₂ policies within a conventional Green Growth narrative (including relaxing energy-availability and net-energy return restrictions, as well as assuming full commercial availability of hydrogen technologies) can contribute to long-term decarbonisation, particularly in applications that are difficult to electrify directly. However, the comparison also shows that most of the climate benefits of the scenarios come from the wider GG policies (e.g., renewables, efficiency, electrification, afforestation, etc.) rather than from hydrogen alone. Differences in the main GHG concentrations among the Green Growth pathways are comparatively modest. Hydrogen should therefore be interpreted as one component of a broader transition, not as a standalone solution, and an option which introduces significant pressure in the energy system and has also significant trade-offs.

It is also worth noting that the timing of the assessment matters. During the first half of the century, a larger roll-out of H₂ may yield slightly worse outcomes than a Green Growth scenario without green H₂ on some indicators, particularly CO₂ emissions. This is because new infrastructure and processes require a faster expansion of the energy system, which cannot be achieved in a low-carbon manner if electrification relies solely on renewable sources. In the longer term, the more ambitious H₂ pathways tend to improve as the system adapts and hydrogen displaces more carbon-intensive end uses.

The analysis also reveals resource and atmospheric trade-offs. High H₂ deployment increases electricity demand and pressure on land through additional renewable capacity (bioenergy and solar), while hydrogen leakages grow rapidly with production and handling. Persistent industrial-process, waste and solvent emissions also limit the depth of decarbonisation, particularly under continued high economic growth.

Another important point to note is that the finding are subject to various limitations and non-ideal conditions. For example, the scenarios are global in scope and assume a broadly uniform policy adoption, while real transitions will differ markedly by region. Also, the exercise assumes that large-scale H₂ technologies will be commercially available and temporarily relaxes certain biophysical feedbacks. Obviously, WILIAM does not cover the entire hydrogen value chain due to its complexity and scale (e.g., the incomplete representation of Carbon Capture and Storage (CCS), residual emissions in some sectors and the bottom-up building dynamics).

The outputs of this activity are crucial for the further development of HYDRA project, as the emissions obtained are used as input data for atmospheric chemistry and climate models, in which the interactions between H₂ and OH, and the half-lives of methane and ozone, can be quantified in greater detail.

Future work within the project will refine these emission scenarios in iteration with the climate and atmospheric chemistry partners, analyse the implications for hydrogen economy of introducing energy-availability and net energy returns constraints, as well as analysing the potential of mitigation strategies to mitigate the trade-offs of hydrogen large-scale deployment.