Effect of Hydrogen Leakage on the Life Cycle Climate Impacts of Hydrogen Supply Chains

doi:10.21203/rs.3.rs-4825556/v1

Hydrogen is of interest for decarbonizing hard-to-abate sectors because it does not produce carbon dioxide when combusted. However, hydrogen has indirect warming effects. In this work, we conducted a life cycle assessment of electrolysis and steam methane reforming to assess their emissions while considering hydrogen’s indirect warming effects. We find that the primary factors influencing life cycle emissions are the production method and related feedstock emissions, rather than the hydrogen leakage and the indirect warming potential of hydrogen. A comparison between fossil fuel-based and hydrogen-based steel production and heavy-duty transportation showed a reduction in greenhouse gas emissions, of approximately 800 to more than 1400 kgCO₂e per tonne of steel and 0.1 to 0.17 kgCO₂e per tonne-km of cargo. While any hydrogen production pathway reduces greenhouse gas emissions for steel, this is not the case for heavy-duty transportation. Therefore, we recommend a nuanced approach in choosing application areas for hydrogen.

Earth and environmental sciences/Climate sciences/Climate change

Earth and environmental sciences/Environmental sciences/Environmental impact

Scientific community and society/Energy and society/Energy policy

Hydrogen is a promising low-carbon and scalable option to decarbonize hard-to-abate industries such as iron and steel production, heavy manufacturing, and heavy-duty transportation [1, 2, 3, 4]. As of August 2024, 61 countries including the United States (US) have official national hydrogen strategies [5]. Other countries, including China, have included hydrogen in their decarbonization and energy plans [6]. Recent energy policies in the US, such as the regional clean hydrogen hubs and the Clean Hydrogen Production Tax Credit in the Inflation Reduction Act (IRA), are set to dramatically increase the production and use of clean hydrogen [7]. Thus, various analyses have projected that hydrogen production and consumption volumes could increase from under 100 Megatonnes (Mt) in 2022 to 530Mt650Mt by 2050 [8, 9, 10, 11]. As governments worldwide have pledged billions in investments toward hydrogen development and expansion quantifying hydrogen greenhouse gas emissions would be beneficial to understanding life cycle climate impacts. For the IRA’s Clean Hydrogen Production Tax Credit, the tax credits issued are dependent on the life cycle greenhouse gas emission intensity of the hydrogen production process in kilograms pf CO₂- equivalent per kilogram of hydrogen (kgCO₂e/kgH₂). Supply chains with lifecycle emissions below 4 kgCO₂e/kgH₂ will qualify for the most generous support [7]. The tax credit requires a well-to-gate lifecycle analysis including emissions associated with feedstock growth, gathering, extraction, processing, and delivery to a hydrogen production facility and emissions associated with the hydrogen production process itself. The hydrogen focused Greenhouse gases, Regulated Emissions, and Energy use in Transportation model (45VH2-GREET) developed by Argonne National Laboratory was designated as the official tool to quantify emissions for tax credit applicants. The 45VH2-GREET model, however, does not account for hydrogen fugitive emissions and leakage nor does it include all hydrogen production methods that may be economically viable. This absence can unintentionally impede innovations that are not currently encompassed within the established repertoire of 45VH2-GREET. Furthermore, the 45VH2-GREET model and, subsequently, the clean hydrogen tax credit assessments do not consider downstream emissions and, therefore, omit a crucial aspect of hydrogen's emission reduction capability through the displacement of current fossil fuels.

Though hydrogen itself is not a greenhouse gas, it interacts with the hydroxyl radical, which is the primary sink for methane. This interaction, increases the atmospheric lifetime of methane, a potent greenhouse gas, and thus, hydrogen indirectly increases radiative forcing [12, 13, 14]. In the troposphere, methane oxidation leads to the production of formaldehyde, which produces hydrogen through photolysis. The natural presence accompanied by increased anthropogenic injection of hydrogen in the atmosphere that can occur through leakage may accentuate this adverse atmospheric interaction. Furthermore, certain hydrogen production pathways such as pyrolysis and steam methane reforming (SMR) rely on a methane feedstock, which can also be leaked, effectively increasing the overall stockpile of atmospheric methane. Moreover, through its interaction with hydroxyl, hydrogen increases tropospheric ozone and produces water vapor which also acts as a greenhouse gas through radiative trapping in the stratosphere [15].

There are uncertainties across the literature concerning the quantification of hydrogen sinks and global hydrogen leakage rates. Gaseous hydrogen is more reactive and has a smaller molecular cross-section than methane and is therefore prone to leak [16]. The leakage rates available in previous studies are obtained from assumptions, calculations, lab experiments, and simulations [17]. These estimates are not uniform across hydrogen production technologies or supply chains. Most studies utilize hydrogen leakage rates ranging from 1–10% to produce estimates of its climate implications. A recent study synthesizing known hydrogen emission rates reported present and future value chain emissions varying between 0.2–20% [17]. In the effort to obtain more accurate hydrogen leakage rates the US Department of Energy (DOE) recently announced a $20 million detection and quantification development initiative [18]. Furthermore, there is a lack of consensus on hydrogen’s global warming potential due to its relatively shorter lifespan of 2.5 years compared to other greenhouse gases [19]. The commonly encountered metrics are global warming potential over 100 years and 20 years (GWP₁₀₀, GWP₂₀), and global temperature potential over 100 years and 20 years (GTP₁₀₀, GTP₂₀). The values reported for hydrogen are 13 ± 5 for GWP₁₀₀, 40 ± 24 for GWP₂₀, 2 ± 1.5 for GTP₁₀₀, and 18 ± 23 for GTP₂₀ [19].

The Hydrogen Council conducted a life cycle assessment (LCA) that considered various pathways envisioned for future hydrogen value chains for 2030 and 2050 [20]. The pathways in the study consist of four autothermal reforming (ATR) plants coupled with 98% capture of total emitted carbon and four electrolysis pathways with onshore or offshore wind and/or solar energy [20]. The end-use applications in their analysis include light-duty vehicle transport, shipping, industrial heat, power generation, fertilizer manufacturing, public transport, and steel production. The analysis includes a comparison between the various hydrogen pathways used and alternative fossil fuel-based or electric-based pathways as appropriate. The results of the study indicated that the effects of using hydrogen range from 60–100% reduction in warming for the respective supply chains relative to current methods, assuming a carbon intensity reduction of the global grid mix [20]. Although this analysis included operational hydrogen venting at production, it omitted fugitive emissions along the supply chain and the indirect warming effects of hydrogen.

Recently, researchers from the Environmental Defense Fund (EDF) conducted a study on the life cycle of hydrogen deployment pathways in which hydrogen leakage and warming effect were taken into consideration [21]. The study was based on the LCA completed by the Hydrogen Council in 2021 [20], but only considered four end uses, notably light-duty vehicle transport, shipping, industrial heat, and power generation, and focused on impacts in 2050. Additionally, carbon capture on ATR hydrogen production was assumed to range from 60–98%. A hydrogen leakage range of 1–10% was assumed across the value chain, and five levels of methane leakage were considered: —extreme low (0.01%), low (0.6%), medium (0.9%), high (2.1%), and extreme high (5.4%). The comparisons between the hydrogen pathways and fossil fuel alternatives were completed using the technology warming potential (over 10, 20, 50 years), which measures the effect of switching from one technology to another, and GWP (over 20 and 100 years). Under extreme cases, the use of hydrogen can produce a 46% increase or a 93% decrease in warming, respectively. This range suggests that better understanding of hydrogen life cycle emissions and warming impacts and appropriate supply chain and end use selection is critical for hydrogen use to yield meaningful climate benefits. Furthermore, electrolysis production pathways appear to be the most consistent in emission reduction (> 60%) regardless of hydrogen leakage and warming effects over different time scales [21]. Despite its thoroughness in terms of hydrogen emissions consideration this study omits two main end uses for hydrogen, notably steel production and heavy-duty transport, which are examined in this work.

Current steel production is responsible for 9% of worldwide carbon dioxide emissions, averaging 1.85 tonne (1850 kg) of CO₂ per tonne of steel produced [22]. Proposed decarbonization strategies for the steel industry include substituting hydrogen and direct reduction for coal used in blast furnaces. Additionally, renewable energy or hydrogen combustion could be used for process heat to reduce or eliminate emissions. Similarly, hydrogen has been proposed as an alternative fuel to reduce heavy duty trucking emissions that currently range from approximately 0.1 to 0.3 kgCO₂e per tonne-km for conventional vehicles operating with diesel [23].

In this work, we aim to fill the existing knowledge gap by including leakage rates and global warming potential to quantify the life cycle climate effects from 1) different hydrogen production pathways then 2) using that hydrogen as an alternative to traditional energy sources for end uses previously omitted in literature. Given the projected growth of hydrogen in the energy mix to meet 2050 decarbonization goals and the concerns that hydrogen might indirectly cause warming that undermines progress towards mitigating climate change, it is valuable to comprehensively assess the impacts of the full life cycle emissions and indirect warming effects of hydrogen. This approach will be demonstrated with novel LCAs of a few sample hydrogen production pathways (electrolysis with grid-tied electricity, electrolysis with carbon-free electricity, SMR, and SMR with CCS) and product manufacturing of steel and heavy-duty transport.

Production:

This study used hydrogen global warming potentials from Hauglustaine., et al [19]. An initial 2% hydrogen leakage was applied to all the production methods to assess the effects of the other variables. Figure 1 shows the results of this standardized leakage reported in kgCO₂e / kgH₂ using GWP₁₀₀ of hydrogen. The difference between the overall greenhouse gas intensity of hydrogen production with and without indirect warming from hydrogen leakage is < 0.5 kgCO₂e /kgH₂ for all pathways considered, which represents less than a 15% increase for electrolysis with grid-tied electricity, steam methane reforming (SMR), and SMR with carbon capture and sequestration (CCS). Consequently, though there is a slight increase in CO₂e emissions when hydrogen’s indirect warming effects are introduced into the model, the carbon intensity of the electricity source and carbon intensity of the production process have a much greater bearing on overall warming potential of hydrogen production.

Figure 2 shows an assessment of the sensitivity to different climate metrics of hydrogen indirect warming effects over time with uniform 2% leakage for all the production methods. The increase in carbon intensity introduced solely by hydrogen warming effects (as opposed to methane) over different time frames is presented through contrast between the base scenario and the inclusion of hydrogen GWP. On average, there is a 0.5 kgCO₂e /kgH₂ difference between GWP₁₀₀ and GWP₂₀ values. With the relatively shorter lifetime of hydrogen, such results align with previous studies that concluded the climate effects of hydrogen are slightly attenuated over time [17, 24].

An assessment of current reported leakage rate projections for 2050 by Esquivel-Elizondo S., et al [17], revealed considerable variation. Electrolysis with renewables has the highest reported leakage rates varying between 2.0% and 9.2%. These relatively high values are due to venting and purging that occur for safety reasons during the electrolysis process. Unabated SMR and SMR coupled with CCS have leakage rates that vary between 0.5% and 1.0%. The detailed leakage rates used for this analysis are outlined in the methods section.

Figure 3 shows that despite relatively high leakage rates, electrolysis had the lowest emissions for the lower and average scenarios and remained comparable in emissions to SMR with CCS even with an upper limit leakage rate. On the other hand, unabated SMR, even with lower hydrogen leakage rates, has the highest overall emissions (partly because of fugitive methane emissions in its supply chain) and fails to meet the DOE clean hydrogen standard of 4.0 kgCO₂e /kgH₂ for well-to-gate life cycle greenhouse emissions. It must be noted our analysis includes a greater scope of emissions then outlined in the 45V guidance (view methods).

Steel Production and Heavy-Duty Transport Case Studies:

Figure 4A and 4B show the decrease in emissions observed with the use of hydrogen for steel production and heavy-duty transport respectively. The results from the steel supply chain LCA include hydrogen leakage and associated indirect warming effects at each stage of the supply chain (production, transportation, and end use). The assessment reveals a minimum 800 kgCO₂e per tonne of steel production (t_steel decrease in the carbon intensity of steel production using hydrogen compared to current fossil fuel-based methods with an average carbon intensity of 1850 kgCO₂e/t steel [22]. Further reduction is observed with decreased carbon intensity of the hydrogen production method. A decrease in emissions ranging from 0.1– 0.17 kgCO₂e per tonne-kilometer (t-km) is observed with hydrogen based heavy duty trucking when using electrolysis powered by wind or solar energy. An increase in emissions (0.79 kgCO₂e /t-km) for heavy duty transportation is observed when using hydrogen from unabated SMR.

Including hydrogen leakage and its associated impact in LCA models only increases the total climate impact of hydrogen production by 0.5 kgCO₂e / kgH₂. These findings suggest that while hydrogen does act as an indirect greenhouse gas, other sources of emissions along the supply chain, including electricity production, fugitive methane emissions, and process emissions, are more significant in the overall climate impact of hydrogen production. Furthermore, even with high hydrogen leakage rates, electrolysis powered by renewables meets the U.S. federal standard of clean hydrogen production with lifecycle emissions intensity below 4 kgCO₂e /kgH₂.

Moreover, by incorporating median leakage values and hydrogen GWP into an existing steel production process it was evident that there is a significant decrease in emissions per tonne of steel produced when shifting from conventional fossil fuel to hydrogen-based steel production, regardless of the production pathway for the hydrogen. In heavy-duty transportation, hydrogen in place of diesel can reduce or exacerbate climate impacts depending on the production pathway. Hydrogen produced via electrolysis with renewables (wind or solar) has lower climate impact while hydrogen produced via SMR and SMR with CCS has a similar or higher carbon intensity compared to current heavy-duty fuels.

Our finding is a need for a nuanced approach in evaluating hydrogen's role in mitigating climate change effects. While hydrogen holds promise as a cleaner energy source, careful consideration of its supply chain, leakage, and indirect climate effects is crucial to ensure meaningful contributions to global decarbonization goals.

The goal of this assessment is to quantify the impact of hydrogen's indirect climate effects and leakage rates on the life cycle emissions of different hydrogen production methods and end uses. We use a life cycle assessment (LCA) model constructed through the Open LCA software and the IPCC 2021 impact assessment method to estimate greenhouse gas emissions intensity of various hydrogen production pathways [26]. The functional unit is the product of concern, which in this case is hydrogen or the concerned end use (highlighted in red in the data tables). Every phase of the life cycle is divided into processes, which are subsequently interconnected through intermediate flows, thereby forming a product system. The data used to conduct this analysis was obtained from the Ecoinvent database [27], a sustainability assessment life cycle inventory, in addition to available hydrogen leakage rates obtained from a study conducted by Esquivel-Elizondo S., et al [17]. The GWP₁₀₀, and GWP₂₀ of hydrogen obtained from a study conducted by Hauglustaine., et al [19] reported in Table 1 were incorporated in the assessment. These values were used in order to understand the warming potential of each production pathway with associated leakage and indirect hydrogen climate impact over time.

Table 1

GWP values for hydrogen from Hauglustaine., et al [19] in this table were added to the IPCC 2021 impact assessment method and used in this study.
Climate Change Metric	Value
GWP₁₀₀	13
GWP₂₀	40

Production:

The production methods taken into consideration in this analysis are unabated SMR (SMR without CCS), SMR coupled with 96% CCS, electrolysis using a grid mix supply of electricity, electrolysis using solar (equivalent kWh not hourly matched), and electrolysis using wind energy (equivalent kWh not hourly matched). Figures 5, 6, and 7 display the system boundaries of the production methods used. The system boundary for the SMR pathways begins with the raw material production and transport of natural gas, deionized water, metallurgical aluminum oxide, magnesium oxide, copper oxide, quicklime, chromium oxide, zinc oxide, zeolite powder, molybdenum trioxide, silica sand, and portafer. Additionally, the embedded emissions of the chemical factory and storage tank are included. The natural gas is sourced from markets in the United States (U.S.), and the remaining inputs are sourced from the global market. The system boundary for the electrolysis pathways begins with deionized water, the designated electricity supplier (grid, solar, wind, or renewable mix) and their capital expenditure (CAPEX) emissions. The electricity for electrolysis is sourced from the Texas Regional Entity (TRE) for grid mix and wind electrolysis and from the Western Electricity Coordinating Council (WECC) for solar (photovoltaic) electrolysis. For all the production processes, the system boundaries stop after the production of hydrogen (that is, at the system gate). Tables 2–5 detail the inputs and outputs of each production process considered in this study.

Table 2

Input parameters for SMR and SMR + CCS production pathways with corresponding units. Oxides: Aluminum oxide, Chromium oxide, Copper oxide, Magnesium oxide, Molybdenum trioxide, Zinc oxide. Natural gas, water oxides, nickel, portafer, quisklime, silica, and zeolite powder data sourced from Ecoinvent. Electricity input for CCS was obtained from NETL [28].
Input Parameters	Values	Units/kg_H2
Natural Gas	4.6	m³
Water (cooling)	0.4	m³
Deionized water	4.4	kg
Oxides	1.40E-03	kg
Nickel	2.00E-04	kg
Portafer	3.00E-04	kg
Quicklime	4.80E-05	kg
Silica	1.20E-05	kg
Zeolite powder	9.00E-04	kg
Electricity (CCS only)	1.15	kWh

Table 3: Output parameters for SMR and SMR+CCS production pathways with corresponding units. Hydrogen leakage data is detailed in Table 7. The remaining data is sourced from Ecoinvent. The hydrogen leakage is emitted to the atmosphere. Stack emissions include acetaldehyde, acetic acid, benzene, benzoapyrene, butane, carbon dioxide, carbon monoxide, dinitrogen monoxide, formaldehyde, mercury, methane, nitrogen oxides, polycyclic aromatic hydrocarbons (PAH), particulate matter, pentane, propane, propionic oxide, sulfur dioxide, and toluene.

Output Parameters	Values	Units
Stack emissions	5.7E-04	kg
Hydrogen	1	kg
Carbon dioxide	9	kg
Carbon dioxide (with CCS)	0.34	kg
Hydrogen Leakage	varies	kg

Table 4

Input parameters for electrolysis production pathways with corresponding units. The electricity input is obtained from the National Energy Technology Laboratory [29] and the deionized water input is obtained from WaterSMART Ltd [30].
Input Parameters	Values	Units
Electricity	40	kWh
Deionized water	9	kg

Table 5: Output parameters for electrolysis production pathways with corresponding units.

Output Parameters	Values	Units
Hydrogen	1	kg
Hydrogen Leakage	varies	kg

The data for the SMR production processes (Tables 2 and 3) are based on an SMR plant assessed by Antonini., et al. [31]. The natural gas is pressurized at 200 bars. The hydrogen yield of the process is enhanced with a water gas shift reaction. In the unabated SMR process, the carbon dioxide exits the plant with the flue gas from the furnace. A separate model for CCS was not built for this LCA, rather a 96.2% capture rate was applied to the total amount of carbon dioxide emitted from the base unabated SMR process, and the subsequent electricity requirements were added as additional input. The electricity input value calculations were based on findings from the National Energy Technology Laboratory [28]. The electricity and water input values for electrolysis were obtained from reports published by the National Renewable Energy Laboratory [29, 32, 33]. This analysis does not take into account specific variations between PEM and alkaline electrolyzers, as the differences are small.

An upper limit, lower limit, and average leakage rates were assessed for each production method to gauge the sensitivity of supply chain greenhouse gas emissions intensity to leakage rates. These leakage rates are detailed in Table 6. An assessment of current reported hydrogen leakage rate projections for 2050 by Esquivel-Elizondo S., et al [17], revealed considerable variation. Electrolysis with renewables has the highest reported leakage rates varying between 2.0% (lower limit) and 9.2% (upper limit). These relatively high values are due to venting and purging that occur for safety reasons as a result of oxygen build up during the electrolysis process. Unabated SMR and SMR with CCS have leakage rates that vary between 0.5% and 1.0%. There are limitations in the leakage values used as they are obtained from simulations or models. There is little to no direct measurement data available on hydrogen leakage. Methane leakage during the SMR processes is < 1% (default in the Ecoinvent database).

Table 6

Hydrogen leakage rates used for the sensitivity analysis. Data obtained from Esquivel-Elizondo S. et al. [17]. Average value represents value calculated for taking the average of 2050 leakage rate predictions.
	Leakage rate	Percentage (%)
SMR	Upper limit	1
	Average	0.8
	Lower limit	0.5
SMR + CCS	Upper limit	1.5
	Average	0.8
	Lower limit	0.6
Electrolysis	Upper limit	9.2
	Average	4.6
	Lower limit	2

Production Model Validation:

A validation was conducted by comparing the results from the models in this study to the Hydrogen Production Emissions Calculator (HyPEC) tool version 1.0, which is based on the GREET model version 2021 [34, 35]. Figure 8 shows the results of this validation, excluding the indirect warming effect of hydrogen. At the time of this analysis, the 45V-GREET had yet to be made available. The difference between the models for all the production pathways considered is less than 2 kgCO₂e / kgH₂. In both models, upstream methane emissions are less than 1%.

Steel Case and Heavy-Duty Transport Case Studies:

The steel and heavy-duty transport pathways selected are based in Texas to mimic future scenarios as one of the DOE hydrogen hubs, Gulf Coast Hydrogen Hub (HyVelocity), is expected to be constructed in Houston. A hydrogen pipeline transportation distance of 400km is assumed with the scenario that the hydrogen would be produced in Houston and used at some location within or on the outskirts of the Texas Triangle. The Texas triangle is defined as the area encompassing Austin, Dallas-Fort Worth, Houston, and San Antonio with the latter three as the corners connected by Interstate 45, Interstate 10, and Interstate 35. The distance chosen for pipeline transport represents the average of the three sides of the Texas triangle rounded up to the nearest hundred. The percentages of hydrogen leaked during pipeline transport and end use consumption used in the model are specified in Table 7. An average leakage rate of 0.3% is assumed during hydrogen pipeline transport [17]. Tables 8 and 9 detail the input and outputs of these end uses, and Figs. 9, and 10 illustrate the system boundaries for the end uses applied in the two supply chains. The gas power plant stack emissions in the electricity supply chain include acenaphthene, acetaldehyde, acetic acid, arsenic ion, benzene, benzo(a)pyrene, beryllium II, butane, cadmium II, carbon monoxide, chromium III, cobalt II. dinitrogen monoxide, dioxins measured as 2,3,7,8-tetrachlorodibenzo-p-dioxin, ethane, formaldehyde, hexane, lead II, manganese II, mercury II, methane, nickel II, nitrogen oxides, PAH, particulate matter, pentane, propane, propionic acid, selenium IV, sulfur dioxide, and toluene [27]. Hydrogen fuel cell trucks have varying characteristics such as on-board hydrogen storage, battery size, fuel cell power, and range which present difficulties in systems level modeling for hydrogen based heavy-duty trucking. For example, the Xcient fuel cell truck with range of 400 km developed by Hyundai has a 72-kWh battery, 190 kW fuel cell power, and can carry 31 kg of hydrogen compressed at 350 bars. The Daimler truck, which was developed by Mercedes Benz and has a range of 1000 km, demonstrated the use of liquid hydrogen (80 kg maximum capacity) with 70 kWh battery size and 300 kW fuel cell power [25]. Consequently, this study only assesses the necessary hydrogen input for transporting 1 tonne over a km obtained with the characteristics of Xcient fuel cell truck.

Table 7

Supply chain hydrogen leakage rates used in the assessment. Data obtained from Esquivel-Elizondo S., et al [17].
	Percentage
Pipeline	0.30%
Steel	0.36%
Heavy Duty Transport	1.60%

Table 8

Inputs for the supply chain end uses assessed in this study and corresponding units. All upstream processes are auto linked by open LCA.
	Input Parameters	Values	Units/kg_H2
Steel Manufacturing	Hydrogen	50	kg
	Iron ore concentrate	1.6	tonne
	Limestone	0.2	tonne
	Water	58	m³
	Electricity (grid mix)	556	kWh
	Pipeline Transportation	400	km
Heavy Duty Transport	Hydrogen	0.09	kg
Heavy Duty Transport	Pipeline transportation	400	km

Table 9: Supply chain outputs and corresponding units. The unit products are highlighted in red.

	Output Parameters	Values	Units
Steel Manufacturing	Steel	1	tonne
Steel Manufacturing	Hydrogen leakage	0.33	kg
Heavy Duty Transport	Heavy duty transport	1	tonne-km
Heavy Duty Transport	Hydrogen leakage	0.0017	kg

Acknowledgments

This work was sponsored by GTI Energy and the Cynthia and George Mitchell Foundation. We thank Michael Lewis (The University of Texas at Austin, Center for Electromechanics) for his contributions to the project. Dr. Webber is on the board of GTI Energy and cofounder and Chairman of Idea Smiths LLC, an engineering consulting firm. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsors, GTI Energy, Cynthia and George Mitchell Foundation, The University of Texas at Austin, or Idea Smiths LLC. The terms of this arrangement have been reviewed and approved by the University of Texas at Austin in accordance with its policy on objectivity in research.

International Energy Agency (2019), The Future of Hydrogen, IEA, Paris https://www.iea.org/reports/the-future-of-hydrogen, License: CC BY 4.0
The Hydrogen Council (Oct 2023), Hydrogen in Decarbonized Energy Systems, https://hydrogencouncil.com/wp-content/uploads/2023/12/Hydrogen-in-Decarbonized-Energy-Systems.pdf
U.S. Department of Energy (Jan 2021), Road Map to a US Hydrogen Economy, https://www.fchea.org/us-hydrogen-study
National Petroleum Council (2024). Harnessing Hydrogen A Key Element of the U.S. Energy Future. Report. https://harnessinghydrogen.npc.org/downloads.php
Corbeau, A.S., Kaswiyanto, R.P., (2024), National Hydrogen Strategies and Roadmap Tracker, Center on Global Energy Policy Columbia, SIPA. https://www.energypolicy.columbia.edu/publications/national-hydrogen-strategies-and-roadmap-tracker/
Nakano, Jane, (March 2022), China Unveils its First Long-Term Hydrogen Plan, Center for Strategic & International Studies, https://www.csis.org/analysis/china-unveils-its-first-long-term-hydrogen-plan
U.S. Department of Energy. (2022, June 6). DOE launches bipartisan infrastructure law’s $8 billion program for clean hydrogen hubs across U.S. https://www.energy.gov/articles/doe-launches-bipartisan-infrastructure-laws-8-billion-program-clean-hydrogen-hubs-across
United Nations Economic Commission for Europe. (2021, November 8). Hydrogen can help decarbonize the economy, through massive investments and appropriate policy support, according to a new UN report [Press release]. UNECE. https://unece.org/circular-economy/press/hydrogen-can-help-decarbonize-economy-through-massive-investments-and
International Energy Agency (2021), Net Zero by 2050, IEA, Paris https://www.iea.org/reports/net-zero-by-2050, License: CC BY 4.0.
Gee, I.M., Glazer, Y.R., Rhodes, J.D., Deetjen, T.A., Webber, M.E., (April 2022). Don’t Mess with Texas: Getting the Lone Star State to Net-Zero by 2050, https://cockrell.utexas.edu/images/pdfs/UT_Texas_Net_Zero_by_2050_April2022_Full_Report.pdf.
U.S. Department of State and US Executive Office of the President. The Long-Term Strategy of the United States: Pathways to Net-Zero Greenhouse Gas Emissions by 2050(Nov 2021). https://www.whitehouse.gov/wp-content/uploads/2021/10/US-Long-Term-Strategy.pdf
Bertagni, M. B., Pacala, S. W., Paulot, F., & Porporato, A. (2022). Risk of the hydrogen economy for atmospheric methane. Nature Communications, 13(1). https://doi.org/10.1038/s41467-022-35419-7
Ocko, I., and Hamburg, S., (Feb 2022) Climate Consequences of Hydrogen Emissions, Atmospheric Chemistry and Physics, https://doi.org/10.5194/acp-22-9349-2022.
Kirschke, S., Bousquet, P., Ciais, P., Saunois, M., Canadell, J. G., Dlugokencky, E. J., Bergamaschi, P., Bergmann, D., Blake, D. R., Bruhwiler, L., Cameron-Smith, P., Castaldi, S., Chevallier, F., Feng, L., Fraser, A., Heimann, M., Hodson, E. L., Houweling, S., Josse, B., … Zeng, G. (2013). Three decades of global methane sources and sinks. Nature Geoscience, 6(10), 813–823. https://doi.org/10.1038/ngeo1955.
Shaddix, C. (2022). An Assessment of Current Understanding of the Greenhouse Gas Impacts from H2 Emissions. Retrieved from https://doi.org/10.2172/1884932
Thawani, B., Hazael, R., Critchley, R. (2024). Numerical modelling of hydrogen leakages in confined spaces for domestic applications. International Journal of Hydrogen Energy. https://doi.org/10.1016/j.ijhydene.2023.12.279
Esquivel-Elizondo, S., Hormaza Mejia, A., Sun ,T., Shrestha, E., Hamburg, SP., & Ocko, IB. (2023). Wide range in estimates of hydrogen emissions from infrastructure, Front. Energy Res. 11:1207208. doi: 10.3389/fenrg.2023.1207208
Advanced Research Projects Agency-Energy (2024). U.S. Department of Energy Announces $20 Million to Develop Cost-Effective, Highly Accurate Hydrogen Detection and Quantification Technologies. Press Release. https://arpa-e.energy.gov/news-and-media/press-releases/us-department-energy-announces-20-million-develop-cost-effective
Hauglustaine, D., Paulot, F., Collins, W., Derwent, R., Sand, M., & Boucher, O. (2022). Climate benefit of a future hydrogen economy. Communications Earth & Environment, 3(1). https://doi.org/10.1038/s43247-022-00626-z
The Hydrogen Council. (2021). Hydrogen Decarbonization Pathways: A Life-Cycle Assessment. https://hydrogencouncil.com/wp-content/uploads/2021/04/Hydrogen-Council-Report_Decarbonization-Pathways_Part-1-Lifecycle-Assessment.pdf
Sun, T., Sherestha, E., Hamburg, S. P., Kupers, R., Ocko, I. B. (2024). Climate Impacts of Hydrogen and Methane Emissions can Considerably Reduce the Climate Benefits across Key Hydrogen Use Cases and Time Scales. Environmental Science & Technology. https://doi.org/10.1021/acs.est.3c09030
Kurrer, C., (2020). European Parliament Briefing. The potential of hydrogen for decarbonizing steel production. https://www.europarl.europa.eu/RegData/etudes/BRIE/2020/641552/EPRS_BRI(2020)641552_EN.pdf
U.S. Environmental Protection Agency. (2023, September 12), Emission Factors for Greenhouse Gas Inventories. https://www.epa.gov/system/files/documents/2023-03/ghg_emission_factors_hub.pdf
Warwick, et al. (March 2023). Atmospheric composition and climate impacts of a future hydrogen economy. Atmospheric Chemistry and Physics. https://doi.org/10.5194/acp-2023-29
Basma, H., Rodriguez, F., (2022). Fuel cell electric tractor-trailers: Technology overview and fuel economy. International Council on Clean Transportation (ICCT). https://theicct.org/wp-content/uploads/2022/07/fuel-cell-tractor-trailer-tech-fuel-1-jul22.pdf
Green Delta Life Cycle and Sustainability Modeling Suite. openLCA. https://www.openlca.org/openlca/ (2022).
Ecoinvent database v.3.10. https://ecoinvent.org/the-ecoinvent-database/
Lewis, E., McNaul, S., Jamieson, M., Henriksen, M.S., Matthews, H. S., Walsh, L., Grove, J., Shultz, T., Skone, T. J., Stevens, R. (2022). Comparison of Commercial, State-of-the-Art, Fossil-Based Hydrogen Production Technologies. National Energy Technology Laboratory. https://doi.org/10.2172/1862910
Kroposki, B., Levene, J., Harrison, K., Sen, P.K., and Novachek, F. (2006). Electrolysis: Information and Opportunities for Electric Power Utilities. https://www.nrel.gov/docs/fy06osti/40605.pdf
Saulnier, R., Minnich, K., Strugess, P.K., (2020). Water for the Hydrogen Economy. Water Smart Solutions Ltd. https://watersmartsolutions.ca/wp-content/uploads/2020/12/Water-for-the-Hydrogen-Economy_WaterSMART-Whitepaper_November-2020.pdf
Antonini, C., Treyer, K., Streb A., van der Spek, M., Bauer, C., Mazzotti, M. (2020). Hydrogen production from natural gas and biomethane with carbon capture and storage – A techno-environmental analysis. Sustainable Energy Fuels, v4, 2967-2986. https://pubs.rsc.org/en/content/articlelanding/2020/se/d0se00222d
Harrison, K W, Remick, R, Hoskin, A, and Martin, G D. (2010). Hydrogen Production: Fundamentals and Case Study Summaries; Preprint. United States: N. p., 2010. Web.
Ivy, J. (2004). Summary of Electrolytic Hydrogen Production: Milestone Completion Report. https://www.nrel.gov/docs/fy04osti/36734.pdf
GTI Energy. (2021). Hydrogen Production Emissions Calculator. https://hypec.gti.energy
Argonne National Laboratory. (2022). Greenhouse Gases, Regulated Emissions, and Energy Use in Transportation Model. https://greet.anl.gov

There is NO Competing Interest.

Effect of Hydrogen Leakage on the Life Cycle Climate Impacts of Hydrogen Supply Chains

Status:

Version 1

Abstract

Figures

INTRODUCTION

RESULTS

Production:

Steel Production and Heavy-Duty Transport Case Studies:

DISCUSSION

METHODS

Production:

Production Model Validation:

Steel Case and Heavy-Duty Transport Case Studies:

Declarations

Acknowledgments

References

Additional Declarations

Status:

Version 1