The impact of net-zero pathways on the international green hydrogen SC is examined through the conduct of a prospective LCA, which is based on the development of renewable resources within the energy grids of the countries under study. The main goal of this study is to conduct a spatial-temporal comparative life cycle SC assessment of five main hydrogen production technologies to generate green hydrogen. This is achieved by developing different SC scenarios that consider the 14 countries involved in technology manufacturing, feedstock production, and hydrogen usage. This study employs a prospective LCA to evaluate the temporal variation in environmental impacts across multiple time horizons, including 2023 (baseline), 2030, 2040, and 2050, in alignment with decade-specific net-zero targets. The system boundary defined in this study comprises raw material extraction, manufacturing of technologies, transportation, O&M, and hydrogen storage. The results are presented for four key impact categories: GW, marine eutrophication (ME), stratospheric ozone depletion (SOD), and human toxicity (HT). These impact categories are emphasized as they encompass critical and diverse aspects of environmental health and sustainability, as determined by the normalized values. Focusing on these categories allows the study to offer a clear and comprehensive overview of the most critical impacts. The Supplementary Information includes an additional 14 midpoint impact categories, providing a broader perspective on the environmental impacts assessed in this study (Supplementary Figs. 1 and 7). The results of the evaluated scenarios for each impact category are presented as follows:
Global warming impact
The GW impact values for all scenarios and technologies are computed across all SC scenarios (Fig. 2a). These findings are derived from environmental impact assessments of the SC, rather than solely focusing on technological impacts. Dark blue bars represent the GW impact results for the year 2023. The analysis indicates that, in the 2023 assessment, the three electrolysis-based SCs demonstrate higher GW impacts compared to the two biomass-based systems. This elevated GW impact primarily stems from the O&M phase of electrolysis technologies, which consume more energy over their operational lifetimes. Another main contributor is the manufacturing phase, driven by the materials used and electricity consumed during the manufacturing process. Among the electrolysis technologies, PEM scenarios exhibit higher GW impacts compared to the other two, with scenario PEM3 showing the highest GW impact among all assessed scenarios and technologies. This higher GW impact is attributed to a major portion of electricity generation from oil, natural gas, and coal in these scenarios. The results indicate that DF4 ISC has the lowest GW impact among all scenarios and systems studied in 2023, although the differences among all DF scenarios are negligible. In all scenarios, considerable reductions in GW values are observed due to the integration of renewable energy sources into the energy mix of all countries. However, the reduction trend varies across each scenario. The most substantial reduction in GW impact is observed in PEM4, decreasing from 18.21 to 0.38 kg CO2eq per kg H2 between 2023 and 2050, while the lowest reduction is seen in DF3, declining from 3.92 kg CO2eq per kg H2 in 2023 to 1.22 kg CO2eq per kg H2 in 2050.
a This plot shows the obtained results for GW impact, b this graph illustrates the ME impact resulting from each scenario, c this plot displays the SOD impact arising from different SC scenarios, and d this graph shows the HT impact of all considered SC scenarios.
Marine eutrophication impact
The ME values for all examined technologies and scenarios are computed (Fig. 2b). The baseline cases, which depict the ME impact in 2023, revealed that the highest ME impact is associated with the AE3 scenario (0.218 kg 1,4-DCB per kg H2). Following this, AE1 and PEM 3 exhibit the highest damaging ME impact. Conversely, SOE4, PEM2, and DF2 demonstrate the lowest ME impact among these scenarios (0.088 kg 1,4-DCB per kg H2). An assessment aimed at achieving net zero within different timeframes shows a declining trend in ME impacts. This decline is attributed to the increased share of renewable resources in the energy mix of all countries. However, this reduction trend is more pronounced for electrolysis technologies compared to the BG and DF scenarios. The smaller reduction in ME impacts associated with BG and DF is mainly due to their lower dependence on the energy mix during both system operation and manufacturing. In contrast, electrolysis systems require significantly more electricity during these phases, leading to greater impacts. The ecotoxicity issues of biomass systems primarily arise from cultivation, crop growth, and the associated toxicity related to feedstock production.
Stratospheric ozone depletion impact
The impacts related to SOD for all examined scenarios are assessed (Fig. 2c). Based on the results from the base cases, PEM3, PEM4, and PEM1 exhibit the highest SOD impact in 2023, respectively. Following the PEM scenarios, AE-related scenarios show a higher SOD impact, followed by SOE technology with a slight difference. However, the SOD impact of BG and DF scenarios in 2023 is significantly lower than that of electrolysis technologies. Surprisingly, the expansion of the renewable resource share in the electricity mix of countries has a notable impact on reducing SOD-related impacts for the three electrolysis systems and their respective scenarios. However, this reduction for biomass-based technologies and scenarios is considerably lower. Interestingly, PEM scenarios, which have the highest SOD impact in 2023, have the potential to significantly reduce this impact by 2050 by achieving the net-zero goal, resulting in the lowest SOD impact. The highest reduction in SOD impact by 2050 is associated with PEM4. It should be noted that in scenarios involving China in manufacturing or O&M, the reduction trend is lower than in other scenarios. This is mainly due to the high proportion of coal and oil-based electricity generation and the longer net-zero target (2060) compared to other considered nations.
Human toxicity impact
The HT of all considered scenarios is evaluated to compare each SC route (Fig. 2d). The findings from the base cases indicate that AE3, AE1, and PEM3 exhibit the highest HT impact compared to other scenarios. The HT impact of the base cases for SOE and DF are similar to each other, while BG’s HT impact is slightly lower. Among all scenarios examined, PEM2 has the lowest base case HT impact in 2023. The subsequent net-zero targets will have a remarkable impact on reducing HT impact. However, it is important to note that even in 2050, the HT impact of AE scenarios remains higher than that of other technologies and scenarios, underscoring the critical nature of this technology. This elevated toxicity issue is attributed to the materials used in the manufacturing process of the Balance of Plant and stack. Additionally, the lowest reduction percentage is observed in BG scenarios, while the highest reduction trend is seen in PEM scenarios. According to the prospective LCA results, in 2050, the lowest HT impact is associated with PEM2 (0.042 kg 1,4-DCB per kg H2), while the highest is related to AE3 (0.189 kg 1,4-DCB per kg H2). Further results for the remaining 14 other midpoint impact categories are provided in Supplementary Fig. 1 in Supplementary Information.
AE phase contributions to global warming
The distribution of phases across all analyzed technologies and SCs is depicted based on four primary impact categories in the year 2050 (Fig. 3). It is evident that the O&M phase serves as the primary contributor to GW impact in AE1 and AE3 scenarios, accounting for approximately 62.59% and 58.80%, respectively (Fig. 3a). Conversely, the manufacturing phase emerges as the main GW impact contributor in AE2 and AE4 scenarios, comprising around 67.00% and 69.42%, respectively. In scenarios where China is the manufacturer or operator of the AE system (AE1 and AE3), the O&M phase continues to show a high GW impact. This is due to China’s projected reliance on fossil-based electricity generation in 2050, which leads to an increased GW impact. This is evident from Fig. 3a, where the GW impact of AE1 and AE3 in 2050 exceeds that of AE2 and AE4 by more than threefold. The manufacturing phase also represents a major contributor to GW impact in AE1 and AE3, accounting for 22.27% and 26.96%, respectively. Additionally, the storage phase contributes to GW impact, while the transportation phase emerges as the least substantial contributor.
These pie charts illustrate each SC phase contribution in GW potential for different developed SC and technologies based on prospective LCA for 2050. a These pie graphs show the results for AE SC scenarios, b these pie graphs display the results for PEM SC scenarios, c these pie graphs show the results for SOE SC scenarios, d these pie graphs illustrate the results for BG SC scenarios, and e these pie graphs show the results for DF SC scenarios.
PEM phase contributions to global warming
The distribution of GW impact across various SC phases for PEM technology in each scenario is evaluated (Fig. 3b). The findings revealed that the storage phase accounts for approximately 55.00% of the total GW impact and serves as the primary contributor in PEM1, PEM2, and PEM4 scenarios. Manufacturing and O&M are the next notable contributors in sequence. However, in PEM3, around 70.00% of the total GW impact stems from the O&M phase, attributed to the utilization of fossil fuel-based electricity generation within China’s grid network in 2050. Additionally, it is observed that transportation has a negligible impact compared to the other phases.
SOE phase contributions to global warming
For each scenario, the distribution of GW impact across different phases of the hydrogen SC for the SOE system is analyzed (Fig. 3c). The findings reveal that the O&M phase contributes approximately 78.00% of the total GW impact, primarily due to the reliance on natural gas for heating during O&M operations. This leads to a higher GW impact compared to other phases. The distribution of phases across all scenarios is largely similar, as all the countries considered in the SOE scenarios have outlined a net-zero plan for 2050, implying that renewable resources should support 100% of the energy mix. To mitigate the GW impact of O&M, the heat required for system operation should be supplied by less pollutant or renewable heat resources, which would significantly reduce environmental impact. The storage and manufacturing phases are the next two notable GW contributors, accounting for approximately 12.30% and 9.20%, respectively.
BG phase contributions to global warming
The analysis examined the contribution of each phase to the GW impact of the BG system in each scenario (Fig. 3d). According to the findings, the O&M phase accounts for the highest GW impact (approximately 65.00%), followed by the manufacturing phase at around 18.00%, and the storage phase at approximately 12.00% of the total GW impact. It is noteworthy that activities, such as biomass production, purification, gasification process, reforming, and pressure swing adsorption, are all encompassed within the O&M phase. The transportation phase has the least impact. Additionally, the pre-treatment of biomass feedstock contributes to only around 2.50% of the total GW impact.
DF phase contributions to global warming
The impact of each SC phase on the GW category for DF technologies in each scenario is depicted (Fig. 3e). It is evident that the manufacturing phase is the primary contributor to GW impact in 2050 for all scenarios. However, the contribution of the manufacturing phase varies across scenarios. DF2 shows the highest portion at 78.80% of the total GW impact, while DF3 exhibits the lowest at 41.10%. The storage phase emerged as the second main contributor to GW impact in all scenarios. However, the transportation phase exhibited a higher GW impact compared to other technologies, especially when the feedstock supplying point is distant from the importer countries. The highest GW impact attributed to transportation is observed in DF 4, accounting for 14.10% of the total GW impact. The O&M phase ranked as the third contributor to GW impact. However, since the energy required for DF operation is lower than that for other technologies, this system exhibits less dependency on the energy mix. The GW impacts by technological phase contributions for 2023, 2030 and 2040 are shown in Supplementary Figs. 2–6. These graphs depict the variations in phase portions from 2023 to 2050, illustrating the effect of the development of the share of renewable resources in energy grids.
Hydrogen’s role in energy resiliency and security
As nations strive to reduce carbon emissions and transition to sustainable energy sources, green hydrogen production emerges as a promising solution. However, the methods used for generating green hydrogen, particularly electrolysis powered by renewable energy, can significantly impact environmental sustainability. According to the findings, the most environmentally sustainable scenario in terms of its GW impact in 2023 is DF2, which involves Ireland and the UK (in the SC with technology manufacturing in Ireland and 50% of capacity exported to the UK). It’s noteworthy that this scenario maintains a low GW impact in 2050 as well, indicating its potential to offer resilience and ensure the production of secured clean fuel. Additionally, while the PEM1 scenario is not deemed sustainable in 2023 (with manufacturing in Norway and 100% export to the USA), it emerges as a resilient solution in 2050.
In terms of ME, the PEM2 scenario offers a resilient and secured energy supply pathway for various timeframes up to 2050. This scenario presents an SC centered around system manufacturing in Canada, with 50% of the output exported to the UK. Moreover, based on the HT impacts, this scenario also emerges as a resilient SC solution. Looking at the environmental impact from the standpoint of SOD, PEM2 offers a pathway for a resilient and secured energy SC, despite its current unsustainable status. Another option is BG1, which involves Austria and Japan. In 2023, BG1 presents a secured SC from the perspective of SOD impact. However, over time, the resilience of this scenario diminishes in terms of sustainability compared to other scenarios.
Overall, the most sustainable IGHSC by 2050 is PEM4, which involves manufacturing in the UK with 50% of the system exported to the USA. This IGHSC route is considered the most resilient and sustainable for the UK. Whilst the environmental impacts of PEM, as demonstrated in their relatively low GW, ME, SOD, and HT in 2050, PEM4 exhibited the highest reduction in GW impact, with around 97.00% decline from 2023 to 2050. PEM3 manufacturing exhibits a consistently lower GW impact compared to the current AE1 scenario, with 2023 values already favoring PEM3 (17.51 vs. 17.55 kg CO2eq per kg H2). This suggests that the UK could start phasing in PEM manufacture immediately without increasing environmental impact. The lowest reduction is seen in DF3, with 69.00% reduction, which involves manufacturing in Poland with 100% export to China. Regarding hydrogen production from biomass, the DF4 scenario demonstrates a lower GW impact than DF3 throughout the period analyzed (3.76 vs. 3.93 kg CO2eq per kg H2 in 2023, declining to 0.73 vs 1.22 kg CO2eq per kg H2 in 2050). Consequently, phasing out hydrogen production via the DF3 pathway in favor of DF4 should commence as soon as possible to maximize environmental benefits.
Technology and SC developments
Technology development consists of several aspects and edges. It can be discussed from different views. One of the main challenges would be material utilization over the manufacturing process, which causes some main environmental issues, such as GW, corrosiveness, toxicity, and acidity. It is necessary to enhance the efficiency of promising methods to compete economically with existing hydrogen production techniques reliant on fossil fuels.
Technological advancements can aid in achieving greater resilience and security in SCs and hydrogen production. The findings indicated that scenarios related to BG and DF are less reliant on the grid network due to lower energy consumption during system operation and manufacturing. However, there’s a need to enhance the resilience of feedstock production and the technological processes involved in production. To ensure competitiveness from an environmental standpoint and enable large-scale application in hydrogen production, it is essential to prioritize the production of sustainable and less polluting feedstock for biomass-based systems. This becomes particularly crucial for mitigating impacts on HT, ME, and SOD, as the results suggest a slower decrease in these impacts for DF and BG SCs compared to electrolysis-based scenarios for hydrogen production.
A major environmental impact of DF SCs arises from the transportation phase, which exhibited a notably higher impact compared to other SCs. PEM SCs demonstrated a higher impact compared to the two other electrolysis-based scenarios. This highlights the urgent need for technical advancements through the use of more sustainable and innovative materials while reducing energy consumption during system operation. This enhancement is essential for improving resilience and ensuring the production of secure hydrogen fuel.
The broadening of the circular economy through innovative technological strategies aligning with regulatory policies aims to guarantee the safe and environmentally sustainable operation of the entire SC38.
Technological SC sustainability ranking
An integrated TOPSIS and fuzzy approach is used to perform the sustainability ranking. A sustainability ranking of the analyzed scenarios is performed using the results from four impact categories in 2023 and 2050 (Fig. 4). Larger markers and lighter colors indicate a more environmentally friendly SC. In essence, a higher score signifies that the SC pathway is less polluting compared to others.
a This plot illustrates the sustainability ranking of all considered scenarios based on GW impact, b this graph presents the sustainability ranking based on ME impact, c this plot displays the sustainability scoring according to SOD impact and d this graph depicts the sustainability scoring according to HT impact category. Circles represent GW, ME, SOD and HT impacts in 2023. Pentagrams represent GW, ME, SOD and HT impacts in 2050. The larger the size and the lighter the colors of the pentagrams and circles, the lower the environmental impacts of the international green hydrogen supply chains.
Results reveal that scenario PEM4 (UK manufacturing with 50% export to the USA) emerges as the most sustainable international SC by 2050. This outcome is supported by the UK’s projected full decarbonization of its electricity grid by 2050 and the relatively clean energy mix and infrastructure in the USA, which together lead to substantial reductions across all impact categories—particularly GW (−97.90%), HT, and SOD.
However, this top-ranking scenario must be interpreted in light of practical trade-offs. PEM systems, while environmentally promising, involve high upfront costs, resource-intensive materials, and technological maturity constraints compared to AE. Moreover, the geopolitical feasibility of transatlantic trade between the UK and the USA may be influenced by regulatory, trade, and infrastructure coordination challenges.
Technology-specific patterns also emerge. Electrolysis technologies (PEM, AE, and SOE) demonstrate the highest sustainability improvement over time, driven by their strong dependency on the electricity grid—which benefits significantly from decarbonization. For example, PEM4 improved from score 2 (2023) to score 20 (2050) in GW impact. In contrast, BG and DF technologies exhibit more gradual and consistent changes, as their impacts are primarily driven by feedstock production and are less influenced by improvements in the energy mix.
Regional insights are also evident. Scenarios involving China in manufacturing or O&M (e.g., AE3, PEM3, DF3) consistently perform poorly across multiple categories even in 2050, primarily due to the country’s slower projected decarbonization (net-zero by 2060) and reliance on coal- and oil-based electricity. This underlines the importance of aligning hydrogen SC planning with national net-zero trajectories.
Impact category differences further influence the rankings. While PEM4 excels in reducing GW and SOD impacts, DF2 and PEM2 perform better in HT, suggesting that no single scenario dominates across all environmental criteria. This reinforces the need for context-specific decision-making, where technology selection and trade partnerships are based on a balance of environmental, economic, and geopolitical factors.
These findings underscore that sustainable hydrogen SCs cannot be universally prescribed but must be tailored to technology type, regional decarbonization pathways, infrastructure readiness, policy alignment, export-import feasibility and long-term decarbonization commitments. Rankings across the remaining 14 impacts categories for 2023 and 2050 are illustrated in Supplementary Fig. 7. Figure 5 maps the green hydrogen SCs, detailing import-export flows across 14 countries and 20 scenarios in 2050.
a This map illustrates the developed supply chain scenarios for AE technology. b This figure shows the expanded supply chain for PEM. c This map displays the defined supply chain for SOE. d This figure shows the determined supply chains for BG system. e This map represents the designed supply chains for DF technology. Both systems and feedstocks are shown in maps related to BG and DF SCs. The GW impact value in 2050 for all SC scenarios is shown in all maps.
Implications of the results
The managerial implications of the spatial-temporal prospective LCA in this study on the IGHSC are considerable. Policymakers and decision-makers can utilize the study’s findings to make informed strategic sustainable decisions about investments for green hydrogen production and its export potential, optimizing SCs for minimal environmental impact. The insights from the 20 IGHSC scenarios help identify the most sustainable and efficient routes for producing, importing, and exporting green hydrogen. Additionally, they highlight optimal transportation strategies, enhancing SC resilience and reducing emissions. Additionally, the study provides a framework to ensure compliance with international environmental regulations and net-zero targets, avoiding potential legal and compliance issues.
From a practical or operational perspective, this study illustrates the hotspots in the green hydrogen SC phases, enabling companies to adopt more sustainable practices for reducing the environmental impact of hydrogen production and transportation. It guides policymakers and industry leaders to consider the longer-term impact in 2030, 2040, and 2050 to meet the net-zero goal through a sustainable route, as indicated in the findings from the IGHSC scenarios as part of the transition to decarbonize the energy grids and to achieve energy independence of the 14 countries. The results highlighted the benefits of certain green hydrogen technologies, informing the selection of the most effective and environmentally sustainable options.
Theoretically, this study contributes to the advancement of spatial-temporal prospective LCA methodologies specifically for IGHSCs. It integrates insights from net-zero goals and energy policies with the economic and trade dynamics of import and export across various SC phases, including raw materials, manufacturing, storage, transport, and end use, for 14 countries. Additionally, it incorporates technological advancements in five green hydrogen technologies. This comprehensive approach enables the emulation of geopolitical, economic, trade, and resource flow scenarios for 20 designed IGHSC scenarios from 2023 to 2050, covering key milestone years, such as 2030 and 2040. This study contributes to sustainability models and fosters interdisciplinary research by connecting environmental science, SC management, and sustainability studies. These contributions and implications collectively emphasize the study’s relevance to academic, policy, and industry stakeholders, providing actionable insights and advancing theoretical frameworks in IGHSCs.
The key findings of this study indicate that, in 2023, the three electrolysis-based SC scenarios exhibited higher global warming impacts compared to the two biomass-based systems. This difference is primarily attributed to the energy-intensive O&M phases, as well as the manufacturing processes associated with electrolysis technologies. By 2050, PEM SC scenarios are projected to be the most environmentally sustainable option. Additionally, aligning with net-zero plans by 2050 will lead to substantial reductions in environmental impacts across all countries, though the magnitude of this reduction will vary depending on the scenario.
The energy mix significantly affects the environmental impact of the IGHSC, with countries relying more on fossil fuels for electricity, resulting in higher ecological impacts. In a similar context, PEM SC exhibits a lower environmental impact compared to the other technologies examined when nations transition to green power in 2050. However, the environmental impact varies significantly across different scenarios, influenced by factors such as the energy mix of specific countries, transportation distances, O&M, and storage conditions.
Environmental impact values vary across different impact categories and are influenced by distinct SC phases. The transportation phase has a minimal impact compared to other phases of the SC for electrolysis systems, but it has a more substantial effect in biomass-based systems. Energy and material inputs are the main contributors that influence the extent of the environmental sustainability of IGHSCs. However, biomass-based systems’ SC are less dependent on the energy mix compared to electrolysis systems due to their lower energy requirements for manufacturing and operation; but the use of sustainable feedstocks and treatment processes is crucial. The feedstock type, including its availability, abundance, and cultivation location, significantly influences the environmental impact of biomass-based hydrogen SCs.
The study demonstrates that the sustainability performance of IGHSCs is not fixed but evolves over time with changes in energy mix, technology maturity, and SC configurations. For instance, while electrolysis-based systems generally show higher GW impacts in 2023, some scenarios like PEM4 achieve massive reductions by 2050 due to cleaner electricity and optimized supply routes. This temporal variation implies that optimum scenarios shift over time, requiring countries to adopt adaptive and forward-looking strategies. Aligning national hydrogen plans with these evolving optimum IGHSCs is practical in principle but challenging in practice, particularly given the uncertainty of future net-zero commitments, policy continuity, and the pace of energy transitions. Such uncertainties may affect infrastructure investment decisions, trade negotiations, and international cooperation. Therefore, flexible policy frameworks, continuous monitoring of technological and geopolitical developments, and dynamic updates to hydrogen strategies are essential. For example, the UK, projected to perform best in PEM4 by 2050, would benefit from early investment in manufacturing capacity and grid decarbonization, while China’s strong role in biomass-based scenarios highlights the importance of domestic feedstock access and resilient trade channels. Overall, alignment is feasible but must be supported by governance structures that account for long-term uncertainty. Pedigree matrix analysis of data quality and Monte Carlo simulation-based uncertainty analysis results (including error bars) are shown in Supplementary Table 4 and Supplementary Fig. 8, respectively.
The study’s findings demonstrate that achieving a sustainable IGHSC by 2050 requires not only a net-zero energy mix but also the use of sustainable materials, a greener transportation system, and the promotion and optimization of production techniques to mitigate impacts across all categories.
