Climate Impacts of Hydrogen and Methane Emissions Can Considerably Reduce the Climate Benefits across Key Hydrogen Use Cases and Time ScalesClick to copy article linkArticle link copied!
- Tianyi Sun*Tianyi Sun*[email protected], +1-512-695-9543Environmental Defense Fund, New York, New York 10010, United StatesMore by Tianyi Sun
- Eriko ShresthaEriko ShresthaEnvironmental Defense Fund, New York, New York 10010, United StatesMore by Eriko Shrestha
- Steven P. HamburgSteven P. HamburgEnvironmental Defense Fund, New York, New York 10010, United StatesMore by Steven P. Hamburg
- Roland Kupers
- Ilissa B. OckoIlissa B. OckoEnvironmental Defense Fund, New York, New York 10010, United StatesMore by Ilissa B. Ocko
Abstract
Recent investments in “clean” hydrogen as an alternative to fossil fuels are driven by anticipated climate benefits. However, most climate benefit calculations do not adequately account for all climate warming emissions and impacts over time. This study reanalyzes a previously published life cycle assessment as an illustrative example to show how the climate impacts of hydrogen deployment can be far greater than expected when including the warming effects of hydrogen emissions, observed methane emission intensities, and near-term time scales; this reduces the perceived climate benefits upon replacement of fossil fuel technologies. For example, for blue (natural gas with carbon capture) hydrogen pathways, the inclusion of upper-end hydrogen and methane emissions can yield an increase in warming in the near term by up to 50%, whereas lower-end emissions decrease warming impacts by at least 70%. For green (renewable-based electrolysis) hydrogen pathways, upper-end hydrogen emissions can reduce climate benefits in the near term by up to 25%. We also consider renewable electricity availability for green hydrogen and show that if it is not additional to what is needed to decarbonize the electric grid, there may be more warming than that seen with fossil fuel alternatives over all time scales. Assessments of hydrogen’s climate impacts should include the aforementioned factors if hydrogen is to be an effective decarbonization tool.
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Synopsis
This study shows that “clean” hydrogen deployment can be significantly better or worse for the climate depending on factors that are not usually considered in life cycle assessment frameworks.
1. Introduction
2. Methods
3. Results
Figure 1
Figure 1. Overview of the life cycle climate impacts of eight hydrogen pathways relative to their fossil fuel alternatives in 2050 considering a range of hydrogen emission rates (1–10%) and methane emission intensities (from extremely low, 0.01%, to extremely high, 5.4%). Each vertical bar represents the range of climate benefits (or disbenefits) by switching to hydrogen from fossil fuels for the best-case scenario (1% hydrogen emissions and a low methane emission intensity of 0.6%) to the worst-case scenario (10% hydrogen emissions and a high methane emissions intensity of 2.1%). Near-term (NT, 20 years) and long-term (LT, 100 years) climate impacts are presented for each pathway. The originally reported climate impacts of these pathways in Hydrogen Council report (2021) are denoted as black triangles. The climate impact of the battery electric alternative for the light-duty vehicle pathway is noted with the letter E.
3.1. Blue Hydrogen Pathways
3.1.1. Effect of Hydrogen Emissions
Figure 2
Figure 2. Life cycle climate impacts of four blue hydrogen pathways relative to their fossil fuel alternatives in 2050 considering a range of 1–10% hydrogen emission rates and medium, 0.9%, methane emission intensity, presented as (a–d) the percentage change in cumulative radiative forcing from continuous emissions over 10, 20, 50, and 100 years after the technology switch and (e–l) annual emissions per function unit (kilometer or kilowatt hour) in CO2e on 20- and 100-year time horizons. Values in panels a–d range from 1% hydrogen emissions (bottom of the bars) to 10% hydrogen emissions (top of the bars). Error bars indicate the uncertainties associated with hydrogen’s radiative efficiency and lifetime. The climate impact of battery electric vehicle relative to fossil fuel is shown as purple horizontal lines in panel a for comparison with blue hydrogen. Percentage changes derived from panels e–l, which are emissions based on the GWP-20 and GWP-100 metrics, are also denoted as “x” (high H2 emissions) and “Δ” (low H2 emissions) in panels a–d. Note that in the case of blue hydrogen, high hydrogen emissions also lead to a small amount of additional methane emissions from increased natural gas use to make up for lost hydrogen (see the Supporting Information for more information).
3.1.2. Effect of Regional Methane Emission Intensity Variations
Figure 3
Figure 3. Life cycle climate impacts of four blue hydrogen pathways relative to their fossil fuel alternatives in 2050 considering a range of hydrogen emission rates of 1–10% (heights of the bars) and three levels of methane emission intensities (different colored bars), presented as the percentage change in cumulative radiative forcing from continuous emissions over 10, 20, 50, and 100 years after the technology switch. The error bars indicate the uncertainties associated with hydrogen’s radiative efficiency and lifetime.
Figure 4
Figure 4. Life cycle climate impacts of four green hydrogen pathways relative to their fossil fuel alternatives in 2050 considering a range of hydrogen emission rates of 1–10%, presented as (a–d) the percentage change in cumulative radiative forcing from continuous emissions over 10, 20, 50, and 100 years after the technology switch and (e–l) annual emissions per function unit (kilometer or kilogram of product) in CO2e on 20- and 100-year time horizons. Values in panels a–d range from 1% hydrogen emissions (bottoms of bars) to 10% hydrogen emissions (tops of bars). The error bars indicate the uncertainties associated with hydrogen’s radiative efficiency and lifetime. Percentage changes derived from panels e–l, which are emissions based on the GWP-20 and GWP-100 metrics, are also denoted as “x” (high H2 emissions) and “Δ” (low H2 emissions) in panels a–d. Note there is a small amount of methane emissions associated with the green hydrogen pathways due to the inclusion of manufacturing emissions associated with the end use equipment.
3.1.3. Effect of Carbon Capture Rates
3.2. Green Hydrogen Pathways
3.2.1. Effect of Hydrogen Emissions
3.2.2. Effect of GHG Emissions Associated with Electricity Supply
Figure 5
Figure 5. Life cycle climate impacts of a green hydrogen fuel cell bus relative to the diesel alternative in 2030 considering a range of hydrogen emission rates of 1–10% and different power supply assumptions (dashed lines), presented as annual emissions per kilometer of vehicle operation in CO2e on 20- and 100-year time horizons. The emission factors of the electricity grid mix in 2030 follow the 1.5 °C-compatible pathway projection by the International Renewable Energy Agency (IRENA). (49) The emission factors of natural gas- and coal-fired power plant are also taken from IRENA. Similar analyses are conducted for the other three green hydrogen pathways and shown in Figure S3.
4. Discussion
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.3c09030.
More detailed information about methods and data used in this study as well as additional figures that show the climate impact of hydrogen pathways relative to other alternatives under the 2030 condition (PDF)
Terms & Conditions
Most electronic Supporting Information files are available without a subscription to ACS Web Editions. Such files may be downloaded by article for research use (if there is a public use license linked to the relevant article, that license may permit other uses). Permission may be obtained from ACS for other uses through requests via the RightsLink permission system: http://pubs.acs.org/page/copyright/permissions.html.
Acknowledgments
The authors thank Ludwig-Bölkow-Systemtechnik GmbH for helping us to understand the data in the Hydrogen Council report and Jane Long and Joan Odgen for insightful discussions that helped improve this study. Results reflect the views of the authors and not necessarily those of the supporting organizations.
References
This article references 63 other publications.
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- 19Prather, M. J. An Environmental Experiment with H2?. Science 2003, 302 (5645), 581– 582, DOI: 10.1126/science.1091060Google Scholar19Atmospheric science: An environmental experiment with H2?Prather, Michael J.Science (Washington, DC, United States) (2003), 302 (5645), 581-582CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A review of the environmental consequences of a H2 fuel economy, including leaks that would cause large increases in atm. H2, affecting stratospheric water vapor, temp. and O3; natural and anthropogenic sources of H2; atm. and soil sinks of H2; indirect greenhouse gas effects; indirect increases of CH4; and NOx redns.
- 20Schultz, M. G.; Diehl, T.; Brasseur, G. P.; Zittel, W. Air Pollution and Climate-Forcing Impacts of a Global Hydrogen Economy. Science 2003, 302 (5645), 624– 627, DOI: 10.1126/science.1089527Google Scholar20Air pollution and climate-forcing impacts of a global hydrogen economySchultz, Martin G.; Diehl, Thomas; Brasseur, Guy P.; Zittel, WernerScience (Washington, DC, United States) (2003), 302 (5645), 624-627CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)If today's surface traffic fleet were powered entirely by H fuel cell technol., anthropogenic emissions of the ozone precursors NOx and CO could be reduced by ≤50%, leading to significant improvements in air quality throughout the Northern Hemisphere. Model simulations of such a scenario predict a decrease in global OH and an increased lifetime of CH4, caused primarily by the redn. of the NOx emissions. The sign of the change in climate forcing caused by CO2 and CH4 depends on the technol. used to generate the H2. A possible rise in atm. H concns. is unlikely to cause significant perturbations of the climate system.
- 21Warwick, N. J.; Bekki, S.; Nisbet, E. G.; Pyle, J. A. Impact of a Hydrogen Economy on the Stratosphere and Troposphere Studied in a 2-D Model. Geophys. Res. Lett. 2004, 31 (5), L05107 DOI: 10.1029/2003GL019224Google Scholar21Impact of a hydrogen economy on the stratosphere and troposphere studied in a 2-D modelWarwick, N. J.; Bekki, S.; Nisbet, E. G.; Pyle, J. A.Geophysical Research Letters (2004), 31 (5), L05107/1-L05107/4CODEN: GPRLAJ; ISSN:0094-8276. (American Geophysical Union)A switch from a fossil fuel to a hydrogen-based energy system could cause significant changes in the magnitude and compn. of anthropogenic emissions. Model simulations suggest the most significant impact of these emission changes would occur in the troposphere, affecting OH. This impact is dependent upon the magnitude and nature of trade-offs in changing fossil fuel use. In the stratosphere, changes in water vapor resulting from expected increases in surface mol. hydrogen emissions via leaks occurring during prodn., transport, and storage, are found to be significantly smaller than previous ests. We conclude that the expected increase in mol. hydrogen emissions is unlikely to have a substantial impact on stratospheric ozone, certainly much smaller than the ozone changes obsd. in the last two decades.
- 22Colella, W. G.; Jacobson, M. Z.; Golden, D. M. Switching to a U.S. Hydrogen Fuel Cell Vehicle Fleet: The Resultant Change in Emissions, Energy Use, and Greenhouse Gases. J. Power Sources 2005, 150, 150– 181, DOI: 10.1016/j.jpowsour.2005.05.092Google Scholar22Switching to a U.S. hydrogen fuel cell vehicle fleet: The resultant change in emissions, energy use, and greenhouse gasesColella, W. G.; Jacobson, M. Z.; Golden, D. M.Journal of Power Sources (2005), 150 (), 150-181CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)This study examines the potential change in primary emissions and energy use as a result of replacing the current U.S. fleet of fossil-fuel on-road vehicles (FFOV) with hybrid elec. fossil fuel vehicles or hydrogen fuel cell vehicles (HFCV). Emissions and energy usage are analyzed for three different HFCV scenarios, with hydrogen produced by (a) steam reforming of natural gas, (b) electrolysis powered by wind energy, and (c) coal gasification. With the U.S. EPA National Emission Inventory as the baseline, other emission inventories are created using a life cycle assessment of alternative fuel supply chains. For a range of reasonable HFCV efficiencies and methods of producing hydrogen, we find that the replacement of FFOV with HFCV significantly reduces emission assocd. with air pollution, compared even with a switch to hybrids. All HFCV scenarios decrease net air pollution emission, including nitrogen oxides, volatile org. compds., particulate matter, ammonia, and carbon monoxide. These redns. are achieved with hydrogen prodn. from either a fossil fuel source such as natural gas or a renewable source such as wind. Furthermore, replacing FFOV with hybrids or HFCV with hydrogen derived from natural gas, wind or coal may reduce the global warming impact of greenhouse gases and particles (measured in carbon dioxide equiv. emission) by 6, 14, 23, and 1%, resp. Finally, even if HFCV are fueled by a fossil fuel such as natural gas, if no carbon is sequestered during hydrogen prodn., and 1% of methane in the feedstock gas is leaked to the environment, natural gas HFCV still may achieve a significant redn. in greenhouse gas and air pollution emission over FFOV.
- 23Wuebbles, D. J. Evaluation of the Potential Environmental Impacts from Large-Scale Use and Production of Hydrogen in Energy and Transportation Applications. 2008. https://digital.library.unt.edu/ark:/67531/metadc841210/ (last accessed 2024-01-12).Google ScholarThere is no corresponding record for this reference.
- 24Frazer-Nash Consultancy. Fugitive Hydrogen Emissions in a Future Hydrogen Economy. 2022. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1067137/fugitive-hydrogen-emissions-future-hydrogen-economy.pdf (last accessed 2024-01-12).Google ScholarThere is no corresponding record for this reference.
- 25Arrigoni, A.; Bravo, D. L. Hydrogen Emissions from a Hydrogen Economy and Their Potential Global Warming Impact. 2022; OP KJ-NA-31-188-EN-N. DOI: 10.2760/065589Google ScholarThere is no corresponding record for this reference.
- 26Cooper, J.; Dubey, L.; Bakkaloglu, S.; Hawkes, A. Hydrogen Emissions from the Hydrogen Value Chain-Emissions Profile and Impact to Global Warming. Sci. Total Environ. 2022, 830, 154624 DOI: 10.1016/j.scitotenv.2022.154624Google Scholar26Hydrogen emissions from the hydrogen value chain-emissions profile and impact to global warmingCooper, Jasmin; Dubey, Luke; Bakkaloglu, Semra; Hawkes, AdamScience of the Total Environment (2022), 830 (), 154624CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)Future energy systems could rely on hydrogen (H2) to achieve decarbonisation and net-zero goals. In a similar energy landscape to natural gas, H2 emissions occur along the supply chain. It has been studied how current gas infrastructure can support H2, but there is little known about how H2 emissions affect global warming as an indirect greenhouse gas. In this work, we have estd. for the first time the potential emission profiles (g CO2eq/MJ H2,HHV) of H2 supply chains, and found that the emission rates of H2 from H2 supply chains and methane from natural gas supply are comparable, but the impact on global warming is much lower based on current ests. This study also demonstrates the crit. importance of establishing mobile H2 emission monitoring and reducing the uncertainty of short-lived H2 climate forcing so as to clearly address H2 emissions for net-zero strategies.
- 27Fan, Z.; Sheerazi, H.; Bhardwaj, A.; Corbeau, A.-S.; Longobardi, K.; Castañeda, A.; Merz, A.-K.; Woodall, C. M.; Agrawal, M.; Orozco-Sanchez, S.; Friedmann, J. Hydrogen Leakage: A Potential Risk for the Hydrogen Economy; Center on Global Energy Policy. 2022. https://www.energypolicy.columbia.edu/publications/hydrogen-leakage-potential-risk-hydrogen-economy/ (last accessed 2024-01-12).Google ScholarThere is no corresponding record for this reference.
- 28Esquivel-Elizondo, S.; Hormaza Mejia, A.; Sun, T.; Shrestha, E.; Hamburg, S. P.; Ocko, I. B. Wide Range in Estimates of Hydrogen Emissions from Infrastructure. Front. Energy Res. 2023, 11, 01– 08, DOI: 10.3389/fenrg.2023.1207208Google ScholarThere is no corresponding record for this reference.
- 29Alvarez, R. A.; Zavala-Araiza, D.; Lyon, D. R.; Allen, D. T.; Barkley, Z. R.; Brandt, A. R.; Davis, K. J.; Herndon, S. C.; Jacob, D. J.; Karion, A.; Kort, E. A.; Lamb, B. K.; Lauvaux, T.; Maasakkers, J. D.; Marchese, A. J.; Omara, M.; Pacala, S. W.; Peischl, J.; Robinson, A. L.; Shepson, P. B.; Sweeney, C.; Townsend-Small, A.; Wofsy, S. C.; Hamburg, S. P. Assessment of Methane Emissions from the U.S. Oil and Gas Supply Chain. Science 2018, 361 (6398), 186– 188, DOI: 10.1126/science.aar7204Google Scholar29Assessment of methane emissions from the U.S. oil and gas supply chainAlvarez, Ramon A.; Zavala-Araiza, Daniel; Lyon, David R.; Allen, David T.; Barkley, Zachary R.; Brandt, Adam R.; Davis, Kenneth J.; Herndon, Scott C.; Jacob, Daniel J.; Karion, Anna; Kort, Eric A.; Lamb, Brian K.; Lauvaux, Thomas; Maasakkers, Joannes D.; Marchese, Anthony J.; Omara, Mark; Pacala, Stephen W.; Peischl, Jeff; Robinson, Allen L.; Shepson, Paul B.; Sweeney, Colm; Townsend-Small, Amy; Wofsy, Steven C.; Hamburg, Steven P.Science (Washington, DC, United States) (2018), 361 (6398), 186-188CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Considerable amts. of the greenhouse gas methane leak from the U.S. oil and natural gas supply chain. Alvarez et al. reassessed the magnitude of this leakage and found that in 2015, supply chain emissions were ∼60% higher than the U.S. Environmental Protection Agency inventory est. They suggest that this discrepancy exists because current inventory methods miss emissions that occur during abnormal operating conditions. These data, and the methodol. used to obtain them, could improve and verify international inventories of greenhouse gases and provide a better understanding of mitigation efforts outlined by the Paris Agreement.
- 30Shen, L.; Gautam, R.; Omara, M.; Zavala-Araiza, D.; Maasakkers, J. D.; Scarpelli, T. R.; Lorente, A.; Lyon, D.; Sheng, J.; Varon, D. J.; Nesser, H.; Qu, Z.; Lu, X.; Sulprizio, M. P.; Hamburg, S. P.; Jacob, D. J. Satellite Quantification of Oil and Natural Gas Methane Emissions in the US and Canada Including Contributions from Individual Basins. Atmos. Chem. Phys. 2022, 22 (17), 11203– 11215, DOI: 10.5194/acp-22-11203-2022Google Scholar30Satellite quantification of oil and natural gas methane emissions in the US and Canada including contributions from individual basinsShen, Lu; Gautam, Ritesh; Omara, Mark; Zavala-Araiza, Daniel; Maasakkers, Joannes D.; Scarpelli, Tia R.; Lorente, Alba; Lyon, David; Sheng, Jianxiong; Varon, Daniel J.; Nesser, Hannah; Qu, Zhen; Lu, Xiao; Sulprizio, Melissa P.; Hamburg, Steven P.; Jacob, Daniel J.Atmospheric Chemistry and Physics (2022), 22 (17), 11203-11215CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)We use satellite methane observations from the Tropospheric Monitoring Instrument (TROPOMI), for May 2018 to Feb. 2020, to quantify methane emissions from individual oil and natural gas (O/G) basins in the US and Canada using a high-resoln. (∼25 km) atm. inverse anal. Our satellite-derived emission ests. show good consistency with in situ field measurements (R = 0.96) in 14 O/G basins distributed across the US and Canada. Aggregating our results to the national scale, we obtain O/G-related methane emission ests. of 12.6 ± 2.1 Tg a-1 for the US and 2.2 ± 0.6 Tg a-1 for Canada, 80% and 40%, resp., higher than the national inventories reported to the United Nations. About 70% of the discrepancy in the US Environmental Protection Agency (EPA) inventory can be attributed to five O/G basins, the Permian, Haynesville, Anadarko, Eagle Ford, and Barnett basins, which in total account for 40% of US emissions. We show more generally that our TROPOMI inversion framework can quantify methane emissions exceeding 0.2-0.5 Tg a-1 from individual O/G basins, thus providing an effective tool for monitoring methane emissions from large O/G basins globally.
- 31Foulds, A.; Allen, G.; Shaw, J. T.; Bateson, P.; Barker, P. A.; Huang, L.; Pitt, J. R.; Lee, J. D.; Wilde, S. E.; Dominutti, P.; Purvis, R. M.; Lowry, D.; France, J. L.; Fisher, R. E.; Fiehn, A.; Pühl, M.; Bauguitte, S. J. B.; Conley, S. A.; Smith, M. L.; Lachlan-Cope, T.; Pisso, I.; Schwietzke, S. Quantification and Assessment of Methane Emissions from Offshore Oil and Gas Facilities on the Norwegian Continental Shelf. Atmos Chem. Phys. 2022, 22 (7), 4303– 4322, DOI: 10.5194/acp-22-4303-2022Google Scholar31Quantification and assessment of methane emissions from offshore oil and gas facilities on the Norwegian continental shelfFoulds, Amy; Allen, Grant; Shaw, Jacob T.; Bateson, Prudence; Barker, Patrick A.; Huang, Langwen; Pitt, Joseph R.; Lee, James D.; Wilde, Shona E.; Dominutti, Pamela; Purvis, Ruth M.; Lowry, David; France, James L.; Fisher, Rebecca E.; Fiehn, Alina; Puhl, Magdalena; Bauguitte, Stephane J. B.; Conley, Stephen A.; Smith, Mackenzie L.; Lachlan-Cope, Tom; Pisso, Ignacio; Schwietzke, StefanAtmospheric Chemistry and Physics (2022), 22 (7), 4303-4322CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)The oil and gas (O&G) sector is a significant source of methane (CH4) emissions. Quantifying these emissions remains challenging, with many studies highlighting discrepancies between measurements and inventory-based ests. In this study, we present CH4 emission fluxes from 21 offshore O&G facilities collected in 10 O&G fields over two regions of the Norwegian continental shelf in 2019. Emissions of CH4 derived from measurements during 13 aircraft surveys were found to range from 2.6 to 1200 t yr-1 (with a mean of 211 t yr-1 across all 21 facilities). Comparing this with aggregated operator-reported facility emissions for 2019, we found excellent agreement (within 1σ uncertainty), with mean aircraft-measured fluxes only 16% lower than those reported by operators. We also compared aircraft-derived fluxes with facility fluxes extd. from a global gridded fossil fuel CH4 emission inventory compiled for 2016. We found that the measured emissions were 42% larger than the inventory for the area covered by this study, for the 21 facilities surveyed (in aggregate). We interpret this large discrepancy not to reflect a systematic error in the operator-reported emissions, which agree with measurements, but rather the representativity of the global inventory due to the methodol. used to construct it and the fact that the inventory was compiled for 2016 (and thus not representative of emissions in 2019). This highlights the need for timely and up-to-date inventories for use in research and policy. The variable nature of CH4 emissions from individual facilities requires knowledge of facility operational status during measurements for data to be useful in prioritising targeted emission mitigation solns. Future surveys of individual facilities would benefit from knowledge of facility operational status over time. Field-specific aggregated emissions (and uncertainty statistics), as presented here for the Norwegian Sea, can be meaningfully estd. from intensive aircraft surveys. However, field-specific ests. cannot be reliably extrapolated to other prodn. fields without their own tailored surveys, which would need to capture a range of facility designs, oil and gas prodn. vols., and facility ages. For year-on-year comparison to annually updated inventories and regulatory emission reporting, analogous annual surveys would be needed for meaningful top-down validation. In summary, this study demonstrates the importance and accuracy of detailed, facility-level emission accounting and reporting by operators and the use of airborne measurement approaches to validate bottom-up accounting.
- 32MacKay, K.; Lavoie, M.; Bourlon, E.; Atherton, E.; O’Connell, E.; Baillie, J.; Fougère, C.; Risk, D. Methane Emissions from Upstream Oil and Gas Production in Canada Are Underestimated. Sci. Rep-uk 2021, 11 (1), 8041, DOI: 10.1038/s41598-021-87610-3Google ScholarThere is no corresponding record for this reference.
- 33Chen, Y.; Sherwin, E. D.; Berman, E. S. F.; Jones, B. B.; Gordon, M. P.; Wetherley, E. B.; Kort, E. A.; Brandt, A. R. Quantifying Regional Methane Emissions in the New Mexico Permian Basin with a Comprehensive Aerial Survey. Environ. Sci. Technol. 2022, 56 (7), 4317– 4323, DOI: 10.1021/acs.est.1c06458Google Scholar33Quantifying Regional Methane Emissions in the New Mexico Permian Basin with a Comprehensive Aerial SurveyChen, Yuanlei; Sherwin, Evan D.; Berman, Elena S. F.; Jones, Brian B.; Gordon, Matthew P.; Wetherley, Erin B.; Kort, Eric A.; Brandt, Adam R.Environmental Science & Technology (2022), 56 (7), 4317-4323CODEN: ESTHAG; ISSN:1520-5851. (American Chemical Society)Limiting emissions of climate-warming methane from oil and gas (O&G) is a major opportunity for short-term climate benefits. We deploy a basin-wide airborne survey of O&G extn. and transportation activities in the New Mexico Permian Basin, spanning 35 923 km2, 26 292 active wells, and over 15 000 km of natural gas pipelines using an independently validated hyperspectral methane point source detection and quantification system. The airborne survey repeatedly visited over 90% of the active wells in the survey region throughout Oct. 2018 to Jan. 2020, totaling approx. 98 000 well site visits. We est. total O&G methane emissions in this area at 194 (+72/-68, 95% CI) metric tonnes per h (t/h), or 9.4% (+3.5%/-3.3%) of gross gas prodn. 50% of obsd. emissions come from large emission sources with persistence-averaged emission rates over 308 kg/h. The fact that a large sample size is required to characterize the heavy tail of the distribution emphasizes the importance of capturing low-probability, high-consequence events through basin-wide surveys when estg. regional O&G methane emissions.
- 34Howarth, R. W.; Jacobson, M. Z. How Green Is Blue Hydrogen?. Energy Sci. Eng. 2021, 9, 1676– 1687, DOI: 10.1002/ese3.956Google Scholar34How green is blue hydrogen?Howarth, Robert W.; Jacobson, Mark Z.Energy Science & Engineering (2021), 9 (10), 1676-1687CODEN: ESENGX; ISSN:2050-0505. (John Wiley & Sons Ltd.)A review. Hydrogen is often viewed as an important energy carrier in a future decarbonized world. Currently, most hydrogen is produced by steam reforming of methane in natural gas ("gray hydrogen"), with high carbon dioxide emissions. Increasingly, many propose using carbon capture and storage to reduce these emissions, producing so-called "blue hydrogen," frequently promoted as low emissions. We undertake the first effort in a peer-reviewed paper to examine the lifecycle greenhouse gas emissions of blue hydrogen accounting for emissions of both carbon dioxide and unburned fugitive methane. Far from being low carbon, greenhouse gas emissions from the prodn. of blue hydrogen are quite high, particularly due to the release of fugitive methane. For our default assumptions (3.5% emission rate of methane from natural gas and a 20-yr global warming potential), total carbon dioxide equiv. emissions for blue hydrogen are only 9%-12% less than for gray hydrogen. While carbon dioxide emissions are lower, fugitive methane emissions for blue hydrogen are higher than for gray hydrogen because of an increased use of natural gas to power the carbon capture. Perhaps surprisingly, the greenhouse gas footprint of blue hydrogen is more than 20% greater than burning natural gas or coal for heat and some 60% greater than burning diesel oil for heat, again with our default assumptions. In a sensitivity anal. in which the methane emission rate from natural gas is reduced to a low value of 1.54%, greenhouse gas emissions from blue hydrogen are still greater than from simply burning natural gas, and are only 18%-25% less than for gray hydrogen. Our anal. assumes that captured carbon dioxide can be stored indefinitely, an optimistic and unproven assumption. Even if true though, the use of blue hydrogen appears difficult to justify on climate grounds.
- 35Stocks, M.; Fazeli, R.; Hughes, L.; Beck, F. J. Global Emissions Implications from Co-Combusting Ammonia in Coal Fired Power Stations: An Analysis of the Japan-Australia Supply Chain. J. Clean. Prod. 2022, 336, 130092 DOI: 10.1016/j.jclepro.2021.130092Google ScholarThere is no corresponding record for this reference.
- 36Ocko, I. B.; Hamburg, S. P. Climate Consequences of Hydrogen Emissions. Atmos. Chem. Phys. 2022, 22, 9349– 9368, DOI: 10.5194/acp-22-9349-2022Google Scholar36Climate consequences of hydrogen emissionsOcko, Ilissa B.; Hamburg, Steven P.Atmospheric Chemistry and Physics (2022), 22 (14), 9349-9368CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)Given the urgency to decarbonize global energy systems, governments and industry are moving ahead with efforts to increase deployment of hydrogen technologies, infrastructure, and applications at an unprecedented pace, including USD billions in national incentives and direct investments. While zero- and low-carbon hydrogen hold great promise to help solve some of the world's most pressing energy challenges, hydrogen is also an indirect greenhouse gas whose warming impact is both widely overlooked and underestimated. This is largely because hydrogen's atm. warming effects are short-lived - lasting only a couple decades - but std. methods for characterizing climate impacts of gases consider only the long-term effect from a one-time pulse of emissions. For gases whose impacts are short-lived, like hydrogen, this long-term framing masks a much stronger warming potency in the near to medium term. This is of concern because hydrogen is a small mol. known to easily leak into the atm., and the total amt. of emissions (e.g., leakage, venting, and purging) from existing hydrogen systems is unknown. Therefore, the effectiveness of hydrogen as a decarbonization strategy, esp. over timescales of several decades, remains unclear. This paper evaluates the climate consequences of hydrogen emissions over all timescales by employing already published data to assess its potency as a climate forcer, evaluate the net warming impacts from replacing fossil fuel technologies with their clean hydrogen alternatives, and est. temp. responses to projected levels of hydrogen demand. We use the std. global warming potential metric, given its acceptance to stakeholders, and incorporate newly published equations that more fully capture hydrogen's several indirect effects, but we consider the effects of const. rather than pulse emissions over multiple time horizons. We account for a plausible range of hydrogen emission rates and include methane emissions when hydrogen is produced via natural gas with carbon capture, usage, and storage (CCUS) ("blue" hydrogen) as opposed to renewables and water ("green" hydrogen). For the first time, we show the strong timescale dependence when evaluating the climate change mitigation potential of clean hydrogen alternatives, with the emission rate detg. the scale of climate benefits or disbenefits. For example, green hydrogen applications with higher-end emission rates (10%) may only cut climate impacts from fossil fuel technologies in half over the first 2 decades, which is far from the common perception that green hydrogen energy systems are climate neutral. However, over a 100-yr period, climate impacts could be reduced by around 80%. On the other hand, lower-end emissions (1%) could yield limited impacts on the climate over all timescales. For blue hydrogen, assocd. methane emissions can make hydrogen applications worse for the climate than fossil fuel technologies for several decades if emissions are high for both gases; however, blue hydrogen yields climate benefits over a 100-yr period. While more work is needed to evaluate the warming impact of hydrogen emissions for specific end-use cases and value-chain pathways, it is clear that hydrogen emissions matter for the climate and warrant further attention from scientists, industry, and governments. This is crit. to informing where and how to deploy hydrogen effectively in the emerging decarbonized global economy.
- 37Bertagni, M. B.; Pacala, S. W.; Paulot, F.; Porporato, A. Risk of the Hydrogen Economy for Atmospheric Methane. Nat. Commun. 2022, 13 (1), 7706, DOI: 10.1038/s41467-022-35419-7Google Scholar37Risk of the hydrogen economy for atmospheric methaneBertagni, Matteo B.; Pacala, Stephen W.; Paulot, Fabien; Porporato, AmilcareNature Communications (2022), 13 (1), 7706CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)Hydrogen (H2) is expected to play a crucial role in reducing greenhouse gas emissions. However, hydrogen losses to the atm. impact atm. chem., including pos. feedback on methane (CH4), the second most important greenhouse gas. Here we investigate through a minimalist model the response of atm. methane to fossil fuel displacement by hydrogen. We find that CH4 concn. may increase or decrease depending on the amt. of hydrogen lost to the atm. and the methane emissions assocd. with hydrogen prodn. Green H2 can mitigate atm. methane if hydrogen losses throughout the value chain are below 9 ± 3%. Blue H2 can reduce methane emissions only if methane losses are below 1%. We address and discuss the main uncertainties in our results and the implications for the decarbonization of the energy sector.
- 38Bauer, C.; Treyer, K.; Antonini, C.; Bergerson, J.; Gazzani, M.; Gencer, E.; Gibbins, J.; Mazzotti, M.; McCoy, S. T.; McKenna, R.; Pietzcker, R.; Ravikumar, A. P.; Romano, M. C.; Ueckerdt, F.; Vente, J.; van der Spek, M. On the Climate Impacts of Blue Hydrogen Production. Sustainable Energy Fuels 2021, 6 (1), 66– 75, DOI: 10.1039/D1SE01508GGoogle ScholarThere is no corresponding record for this reference.
- 39Ricks, W.; Xu, Q.; Jenkins, J. D. Minimizing Emissions from Grid-Based Hydrogen Production in the United States. Environ. Res. Lett. 2023, 18 (1), 014025 DOI: 10.1088/1748-9326/acacb5Google ScholarThere is no corresponding record for this reference.
- 40Alvarez, R. A.; Pacala, S. W.; Winebrake, J. J.; Chameides, W. L.; Hamburg, S. P. Greater Focus Needed on Methane Leakage from Natural Gas Infrastructure. Proc. National Acad. Sci. 2012, 109 (17), 6435– 6440, DOI: 10.1073/pnas.1202407109Google Scholar40Greater focus needed on methane leakage from natural gas infrastructureAlvarez, Ramon A.; Pacala, Stephen W.; Winebrake, James J.; Chameides, William L.; Hamburg, Steven P.Proceedings of the National Academy of Sciences of the United States of America (2012), 109 (17), 6435-6440, S6435/1-S6435/7CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)Natural gas is seen by many as the future of American energy: a fuel that can provide energy independence and reduce greenhouse gas emissions in the process. However, there has also been confusion about the climate implications of increased use of natural gas for elec. power and transportation. We propose and illustrate the use of technol. warming potentials as a robust and transparent way to compare the cumulative radiative forcing created by alternative technologies fueled by natural gas and oil or coal by using the best available ests. of greenhouse gas emissions from each fuel cycle (i.e., prodn., transportation and use). We find that a shift to compressed natural gas vehicles from gasoline or diesel vehicles leads to greater radiative forcing of the climate for 80 or 280 yr, resp., before beginning to produce benefits. Compressed natural gas vehicles could produce climate benefits on all time frames if the well-to-wheels CH4 leakage were capped at a level 45-70% below current ests. By contrast, using natural gas instead of coal for elec. power plants can reduce radiative forcing immediately, and reducing CH4 losses from the prodn. and transportation of natural gas would produce even greater benefits. There is a need for the natural gas industry and science community to help obtain better emissions data and for increased efforts to reduce methane leakage in order to minimize the climate footprint of natural gas.
- 41Ocko, I. B.; Hamburg, S. P. Climate Impacts of Hydropower: Enormous Differences among Facilities and over Time. Environ. Sci. Technol. 2019, 53 (23), 14070– 14082, DOI: 10.1021/acs.est.9b05083Google Scholar41Climate Impacts of Hydropower: Enormous Differences among Facilities and over TimeOcko, Ilissa B.; Hamburg, Steven P.Environmental Science & Technology (2019), 53 (23), 14070-14082CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)To stabilize climate, humans must rapidly displace fossil fuels with clean energy technologies. Currently, hydropower dominates renewable electricity generation, accounting for 2/3 globally; it is expected to grow at least 45% by 2040. While it is broadly assumed that hydropower facilities emit greenhouse gases on par with wind, there is mounting evidence that emissions can be considerably greater, with some facilities even on par with fossil fuels. However, analyses of climate impacts of hydropower facilities have been simplistic, emphasizing aggregated 100-yr impacts from a one-year emissions pulse. Such analyses mask near-term impacts of CH4 emissions central to many current policy regimes, tending to omit CO2 emissions assocd. with initial facility development, and not considering the effect of atm. gas accumulation over time. An analytic approach which addresses these issues was developed. By analyzing climate impacts of sustained hydropower emissions over time, the authors detd. there are enormous differences in climate impacts among facilities and over time. If minimizing climate impacts are not a priority for design and construction of new hydropower facilities, it could lead to limited or even no climate benefits.
- 42Tromp, T. K.; Shia, R.-L.; Allen, M.; Eiler, J. M.; Yung, Y. L. Potential Environmental Impact of a Hydrogen Economy on the Stratosphere. Science 2003, 300 (5626), 1740– 1742, DOI: 10.1126/science.1085169Google Scholar42Potential Environmental Impact of a Hydrogen Economy on the StratosphereTromp, Tracey K.; Shia, Run-Lie; Allen, Mark; Eiler, John M.; Yung, Y. L.Science (Washington, DC, United States) (2003), 300 (5626), 1740-1742CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)The widespread use of hydrogen fuel cells could have hitherto unknown environmental impacts due to unintended emissions of mol. hydrogen, including an increase in the abundance of water vapor in the stratosphere (plausibly by as much as ∼1 part per million by vol.). This would cause stratospheric cooling, enhancement of the heterogeneous chem. that destroys ozone, an increase in noctilucent clouds, and changes in tropospheric chem. and atm.-biosphere interactions.
- 43Jacobson, M. Z.; Colella, W. G.; Golden, D. M. Cleaning the Air and Improving Health with Hydrogen Fuel-Cell Vehicles. Science 2005, 308 (5730), 1901– 1905, DOI: 10.1126/science.1109157Google Scholar43Cleaning the Air and Improving Health with Hydrogen Fuel-Cell VehiclesJacobson, M. Z.; Colella, W. G.; Golden, D. M.Science (Washington, DC, United States) (2005), 308 (5730), 1901-1905CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A review. Converting all U.S. onroad vehicles to hydrogen fuel-cell vehicles (HFCVs) may improve air quality, health, and climate significantly, whether the hydrogen is produced by steam reforming of natural gas, wind electrolysis, or coal gasification. Most benefits would result from eliminating current vehicle exhaust. Wind and natural gas HFCVs offer the greatest potential health benefits and could save 3700 to 6400 U.S. lives annually. Wind HFCVs should benefit climate most. An all-HFCV fleet would hardly affect tropospheric water vapor concns. Conversion to coal HFCVs may improve health but would damage climate more than fossil/elec. hybrids. The real cost of hydrogen from wind electrolysis may be below that of U.S. gasoline.
- 44Jacobson, M. Z. Effects of Wind-powered Hydrogen Fuel Cell Vehicles on Stratospheric Ozone and Global Climate. Geophys. Res. Lett. 2008, 35 (19), L19803 DOI: 10.1029/2008GL035102Google Scholar44Effects of wind-powered hydrogen fuel cell vehicles on stratospheric ozone and global climateJacobson, Mark Z.Geophysical Research Letters (2008), 35 (19), L19803/1-L19803/5CODEN: GPRLAJ; ISSN:0094-8276. (American Geophysical Union)A review. Converting the world's fossil-fuel onroad vehicles (FFOV) to hydrogen fuel cell vehicles (HFCV), where the H2 is produced by wind-powered electrolysis, is estd. to reduce global fossil, biofuel, and biomass-burning emissions of CO2 by ∼13.4%, NOx ∼23.0%, nonmethane org. gases ∼18.9%, black carbon ∼8% H2 ∼3.2% (at 3% leakage), and H2O ∼0.2%. Over 10 years, such redns. were calcd. to reduce tropospheric CO ∼5%, NOx ∼5-13%, most org. gases ∼3-15%, OH ∼4%, ozone ∼6%, and PAN ∼13%, but to increase tropospheric CH4 ∼0.25% due to the lower OH. Lower OH also increased upper tropospheric/lower stratospheric ozone, increasing its global column by ∼0.41%. WHFCV cooled the troposphere and warmed the stratosphere, reduced aerosol and cloud surface areas, and increased pptn. Other renewable-powered HFCV or battery elec. vehicles should have similar impacts.
- 45van Ruijven, B.; Lamarque, J.-F.; van Vuuren, D. P.; Kram, T.; Eerens, H. Emission Scenarios for a Global Hydrogen Economy and the Consequences for Global Air Pollution. Global Environ. Change 2011, 21 (3), 983– 994, DOI: 10.1016/j.gloenvcha.2011.03.013Google ScholarThere is no corresponding record for this reference.
- 46Bond, S. W.; Gül, T.; Reimann, S.; Buchmann, B.; Wokaun, A. Emissions of Anthropogenic Hydrogen to the Atmosphere during the Potential Transition to an Increasingly H2-Intensive Economy. Int. J. Hydrogen Energ 2011, 36 (1), 1122– 1135, DOI: 10.1016/j.ijhydene.2010.10.016Google Scholar46Emissions of anthropogenic hydrogen to the atmosphere during the potential transition to an increasingly H2-intensive economyBond, S. W.; Guel, T.; Reimann, S.; Buchmann, B.; Wokaun, A.International Journal of Hydrogen Energy (2011), 36 (1), 1122-1135CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)Current and future anthropogenic atm. H2 emissions from technol. processes were assessed. Current emissions are dominated by direct exhaust gas of road-based motor vehicles and losses during industrial H2 prodn. from fossil fuels. H2 emissions from transportation were estd. to be 4.5 Tg for 2010. An addnl. ∼0.5-2 Tg H2 were estd. to be lost to the atm. from industrial processes in 2010. In 2020, emissions from transportation are estd. to be ∼50% of those in 2010. Future emissions will occur as losses along the entire prodn., distribution, and end-use chain, including emissions from H2 fuel cell vehicles (FCV). In 2050, overall anthropogenic H2 emissions will only approach current levels at high-end loss rates; direct emissions from transportation are expected to be significantly lower than current levels. In 2100, an av. 0.5% loss rate would result in overall H2 emissions exceeding current levels, even with no net H2 emissions from FCV; however, based on an av. 0.1% loss rate, H2 emission factors from FCV on the order of 120-170 mg/km are projected to result in overall anthropogenic H2 emissions similar to 2010 levels.
- 47IEA. Global Methane Tracker Documentation 2022 Version. 2022. https://iea.blob.core.windows.net/assets/b5f6bb13-76ce-48ea-8fdb-3d4f8b58c838/GlobalMethaneTracker_documentation.pdf (last accessed 2024-01-12).Google ScholarThere is no corresponding record for this reference.
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- 50Bertagni, M. B.; Socolow, R. H.; Martirez, J. M. P.; Carter, E. A.; Greig, C.; Ju, Y.; Lieuwen, T.; Mueller, M. E.; Sundaresan, S.; Wang, R.; Zondlo, M. A.; Porporato, A. Minimizing the Impacts of the Ammonia Economy on the Nitrogen Cycle and Climate. Proc. Natl. Acad. Sci. United States Am. 2023, 120 (46), e2311728120 DOI: 10.1073/pnas.2311728120Google ScholarThere is no corresponding record for this reference.
- 51Wolfram, P.; Kyle, P.; Zhang, X.; Gkantonas, S.; Smith, S. Using Ammonia as a Shipping Fuel Could Disturb the Nitrogen Cycle. Nat. Energy 2022, 7 (12), 1112– 1114, DOI: 10.1038/s41560-022-01124-4Google Scholar51Using ammonia as a shipping fuel could disturb the nitrogen cycleWolfram, Paul; Kyle, Page; Zhang, Xin; Gkantonas, Savvas; Smith, StevenNature Energy (2022), 7 (12), 1112-1114CODEN: NEANFD; ISSN:2058-7546. (Nature Portfolio)A polemic in response to Paul Wolfram et al is given. Ammonia has been proposed as a shipping fuel, yet potential adverse side-effects are poorly understood. We argue that if nitrogen releases from ammonia are not tightly controlled, the scale of the demands of maritime transport are such that the global nitrogen cycle could be substantially altered.
- 52Schaller, K. V.; Gruber, C. Hydrogen Powered Fuel-Cell Buses Meet Future Transport Challenges. 2001. https://www.citelec.org/eledrive/Afuelcellarticles/PP301.PDF (last accessed 2024-01-12).Google ScholarThere is no corresponding record for this reference.
- 53Marcinkoski, J.; Vijayagopal, R.; Adams, J.; James, B.; Kopasz, J.; Ahluwalia, R. DOE Advanced Truck Technologies: Subsection of the Electrified Powertrain Roadmap Technical Targets for Hydrogen-Fueled Long-Haul Tractor-Trailer Trucks. 2019. https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf?Status=Master (last accessed 2024-01-12).Google ScholarThere is no corresponding record for this reference.
- 54Ueckerdt, F.; Bauer, C.; Dirnaichner, A.; Everall, J.; Sacchi, R.; Luderer, G. Potential and Risks of Hydrogen-Based e-Fuels in Climate Change Mitigation. Nat. Clim Change 2021, 11 (5), 384– 393, DOI: 10.1038/s41558-021-01032-7Google Scholar54Potential and risks of hydrogen-based e-fuels in climate change mitigationUeckerdt, Falko; Bauer, Christian; Dirnaichner, Alois; Everall, Jordan; Sacchi, Romain; Luderer, GunnarNature Climate Change (2021), 11 (5), 384-393CODEN: NCCACZ; ISSN:1758-6798. (Nature Portfolio)Abstr.: E-fuels promise to replace fossil fuels with renewable electricity without the demand-side transformations required for a direct electrification. However, e-fuels' versatility is counterbalanced by their fragile climate effectiveness, high costs and uncertain availability. E-fuel mitigation costs are euro800-1,200 per tCO2. Large-scale deployment could reduce costs to euro20-270 per tCO2 until 2050, yet it is unlikely that e-fuels will become cheap and abundant early enough. Neglecting demand-side transformations threatens to lock in a fossil-fuel dependency if e-fuels fall short of expectations. Sensible climate policy supports e-fuel deployment while hedging against the risk of their unavailability at large scale. Policies should be guided by a 'merit order of end uses' that prioritizes hydrogen and e-fuels for sectors that are inaccessible to direct electrification.
- 55Gudmundsson, O.; Thorsen, J. E. Source-to-Sink Efficiency of Blue and Green District Heating and Hydrogen-Based Heat Supply Systems. Smart Energy 2022, 6, 100071 DOI: 10.1016/j.segy.2022.100071Google Scholar55Source-to-sink efficiency of blue and green district heating and hydrogen-based heat supply systemsGudmundsson, Oddgeir; Thorsen, Jan EricSmart Energy (2022), 6 (), 100071CODEN: SEMNBM; ISSN:2666-9552. (Elsevier Ltd.)Hydrogen is commonly mentioned as a future proof energy carrier. Hydrogen supporters advocate for repurposing existing natural gas grids for a sustainable hydrogen supply. While the long-term vision of the hydrogen community is green hydrogen the community acknowledges that in the short term it will be to large extent manufd. from natural gas, but in a decarbonized way, giving it the name blue hydrogen. While hydrogen has a role to play in hard to decarbonize sectors its role for building heating demands is doubtful, as mature and more energy efficient alternatives exist. As building heat supply infrastructures built today will operate for the decades to come it is of highest importance to ensure that the most efficient and sustainable infrastructures are chosen. This paper compares the source to sink efficiencies of hydrogen-based heat supply system to a district heating system operating on the same primary energy source. The results show that a natural gas-based district heating could be 267% more efficient, and consequently have significantly lower global warming potential, than a blue hydrogen-based heat supply A renewable power-based district heating could achieve above 440% higher efficiency than green hydrogen-based heat supply system.
- 56de Kleijne, K.; de Coninck, H.; van Zelm, R.; Huijbregts, M. A. J.; Hanssen, S. V. The Many Greenhouse Gas Footprints of Green Hydrogen. Sustainable Energy Fuels 2022, 6, 4383– 4387, DOI: 10.1039/D2SE00444EGoogle Scholar56The many greenhouse gas footprints of green hydrogende Kleijne, Kiane; de Coninck, Heleen; van Zelm, Rosalie; Huijbregts, Mark A. J.; Hanssen, Steef V.Sustainable Energy & Fuels (2022), 6 (19), 4383-4387CODEN: SEFUA7; ISSN:2398-4902. (Royal Society of Chemistry)Green hydrogen could contribute to climate change mitigation, but its greenhouse gas footprint varies with electricity source and allocation choices. Using life-cycle assessment we conclude that if electricity comes from addnl. renewable capacity, green hydrogen outperforms fossil-based hydrogen. In the short run, alternative uses of renewable electricity likely achieve greater emission redns.
- 57CE Delft. Additionality of Renewable Electricity for Green Hydrogen Production in the EU. 2022. https://cedelft.eu/wp-content/uploads/sites/2/2022/12/CE_Delft_220358_Final_report.pdf (last accessed 2024-01-12).Google ScholarThere is no corresponding record for this reference.
- 58Wolak, F. Re: Section 45V Credit for Production of Clean Hydrogen and Additionality. 2023. https://static1.squarespace.com/static/53ab1feee4b0bef0179a1563/t/6452ad18d54ae3543c305f15/1683139864709/FCHEA+Additionality+Sign+On+Letter+Final+2023-5-4.pdf (last accessed 2024-01-12).Google ScholarThere is no corresponding record for this reference.
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- 60Ocko, I. B.; Hamburg, S. P.; Jacob, D. J.; Keith, D. W.; Keohane, N. O.; Oppenheimer, M.; Roy-Mayhew, J. D.; Schrag, D. P.; Pacala, S. W. Unmask Temporal Trade-Offs in Climate Policy Debates. Science 2017, 356 (6337), 492– 493, DOI: 10.1126/science.aaj2350Google Scholar60Unmask temporal trade-offs in climate policy debatesOcko, Ilissa B.; Hamburg, Steven P.; Jacob, Daniel J.; Keith, David W.; Keohabne, Nathaniel O.; Oppenheimer, Michael; Roy-Mayhew, Joseph D.; Schrag, Daniel P.; Pacala, Stephen W.Science (Washington, DC, United States) (2017), 356 (6337), 492-493CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)There is no expanded citation for this reference.
- 61Deng, H.; Bielicki, J. M.; Oppenheimer, M.; Fitts, J. P.; Peters, C. A. Leakage Risks of Geologic CO2 Storage and the Impacts on the Global Energy System and Climate Change Mitigation. Clim. Chang. 2017, 144 (2), 151– 163, DOI: 10.1007/s10584-017-2035-8Google Scholar61Leakage risks of geologic CO2 storage and the impacts on the global energy system and climate change mitigationDeng, Hang; Bielicki, Jeffrey M.; Oppenheimer, Michael; Fitts, Jeffrey P.; Peters, Catherine A.Climatic Change (2017), 144 (2), 151-163CODEN: CLCHDX; ISSN:0165-0009. (Springer)This study investigated how subsurface and atm. leakage from geol. CO2 storage reservoirs could impact the deployment of Carbon Capture and Storage (CCS) in the global energy system. The Leakage Risk Monetization Model was used to est. the costs of leakage for representative CO2 injection scenarios, and these costs were incorporated into the Global Change Assessment Model. Worst-case scenarios of CO2 leakage risk, which assume that all leakage pathway permeabilities are extremely high, were simulated. Even with this extreme assumption, the assocd. costs of monitoring, treatment, containment, and remediation resulted in minor shifts in the global energy system. For example, the redn. in CCS deployment in the electricity sector was 3% for the "high" leakage scenario, with replacement coming from fossil fuel and biomass without CCS, nuclear power, and renewable energy. In other words, the impact on CCS deployment under a realistic leakage scenario is likely to be negligible. We also quantified how the resulting shifts will impact atm. CO2 concns. Under a carbon tax that achieves an atm. CO2 concn. of 480 ppm in 2100, technol. shifts due to leakage costs would increase this concn. by less than 5 ppm. It is important to emphasize that this increase does not result from leaked CO2 that reaches the land surface, which is minimal due to secondary trapping in geol. strata above the storage reservoir. The overall conclusion is that leakage risks and assocd. costs will likely not interfere with the effectiveness of policies for climate change mitigation.
- 62Vinca, A.; Emmerling, J.; Tavoni, M. Bearing the Cost of Stored Carbon Leakage. Front. Energy Res. 2018, 6, 40, DOI: 10.3389/fenrg.2018.00040Google ScholarThere is no corresponding record for this reference.
- 63Hidden hydrogen: Earth may hold vast stores of a renewable, carbon-free fuel. Science https://www.science.org/content/article/hidden-hydrogen-earth-may-hold-vast-stores-renewable-carbon-free-fuel (last accessed 2024-01-12).Google ScholarThere is no corresponding record for this reference.
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Abstract
Figure 1
Figure 1. Overview of the life cycle climate impacts of eight hydrogen pathways relative to their fossil fuel alternatives in 2050 considering a range of hydrogen emission rates (1–10%) and methane emission intensities (from extremely low, 0.01%, to extremely high, 5.4%). Each vertical bar represents the range of climate benefits (or disbenefits) by switching to hydrogen from fossil fuels for the best-case scenario (1% hydrogen emissions and a low methane emission intensity of 0.6%) to the worst-case scenario (10% hydrogen emissions and a high methane emissions intensity of 2.1%). Near-term (NT, 20 years) and long-term (LT, 100 years) climate impacts are presented for each pathway. The originally reported climate impacts of these pathways in Hydrogen Council report (2021) are denoted as black triangles. The climate impact of the battery electric alternative for the light-duty vehicle pathway is noted with the letter E.
Figure 2
Figure 2. Life cycle climate impacts of four blue hydrogen pathways relative to their fossil fuel alternatives in 2050 considering a range of 1–10% hydrogen emission rates and medium, 0.9%, methane emission intensity, presented as (a–d) the percentage change in cumulative radiative forcing from continuous emissions over 10, 20, 50, and 100 years after the technology switch and (e–l) annual emissions per function unit (kilometer or kilowatt hour) in CO2e on 20- and 100-year time horizons. Values in panels a–d range from 1% hydrogen emissions (bottom of the bars) to 10% hydrogen emissions (top of the bars). Error bars indicate the uncertainties associated with hydrogen’s radiative efficiency and lifetime. The climate impact of battery electric vehicle relative to fossil fuel is shown as purple horizontal lines in panel a for comparison with blue hydrogen. Percentage changes derived from panels e–l, which are emissions based on the GWP-20 and GWP-100 metrics, are also denoted as “x” (high H2 emissions) and “Δ” (low H2 emissions) in panels a–d. Note that in the case of blue hydrogen, high hydrogen emissions also lead to a small amount of additional methane emissions from increased natural gas use to make up for lost hydrogen (see the Supporting Information for more information).
Figure 3
Figure 3. Life cycle climate impacts of four blue hydrogen pathways relative to their fossil fuel alternatives in 2050 considering a range of hydrogen emission rates of 1–10% (heights of the bars) and three levels of methane emission intensities (different colored bars), presented as the percentage change in cumulative radiative forcing from continuous emissions over 10, 20, 50, and 100 years after the technology switch. The error bars indicate the uncertainties associated with hydrogen’s radiative efficiency and lifetime.
Figure 4
Figure 4. Life cycle climate impacts of four green hydrogen pathways relative to their fossil fuel alternatives in 2050 considering a range of hydrogen emission rates of 1–10%, presented as (a–d) the percentage change in cumulative radiative forcing from continuous emissions over 10, 20, 50, and 100 years after the technology switch and (e–l) annual emissions per function unit (kilometer or kilogram of product) in CO2e on 20- and 100-year time horizons. Values in panels a–d range from 1% hydrogen emissions (bottoms of bars) to 10% hydrogen emissions (tops of bars). The error bars indicate the uncertainties associated with hydrogen’s radiative efficiency and lifetime. Percentage changes derived from panels e–l, which are emissions based on the GWP-20 and GWP-100 metrics, are also denoted as “x” (high H2 emissions) and “Δ” (low H2 emissions) in panels a–d. Note there is a small amount of methane emissions associated with the green hydrogen pathways due to the inclusion of manufacturing emissions associated with the end use equipment.
Figure 5
Figure 5. Life cycle climate impacts of a green hydrogen fuel cell bus relative to the diesel alternative in 2030 considering a range of hydrogen emission rates of 1–10% and different power supply assumptions (dashed lines), presented as annual emissions per kilometer of vehicle operation in CO2e on 20- and 100-year time horizons. The emission factors of the electricity grid mix in 2030 follow the 1.5 °C-compatible pathway projection by the International Renewable Energy Agency (IRENA). (49) The emission factors of natural gas- and coal-fired power plant are also taken from IRENA. Similar analyses are conducted for the other three green hydrogen pathways and shown in Figure S3.
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This article references 63 other publications.
- 1Hydrogen Council. Hydrogen Insights 2023: An Update on the State of the Global Hydrogen Economy, with a Deep Dive into North America. 2023. https://hydrogencouncil.com/wp-content/uploads/2023/05/Hydrogen-Insights-2023.pdf (last accessed 2024-01-12).There is no corresponding record for this reference.
- 2Valente, A.; Iribarren, D.; Dufour, J. Life Cycle Assessment of Hydrogen Energy Systems: A Review of Methodological Choices. Int. J. Life Cycle Assess. 2017, 22 (3), 346– 363, DOI: 10.1007/s11367-016-1156-z2Life cycle assessment of hydrogen energy systems: a review of methodological choicesValente, Antonio; Iribarren, Diego; Dufour, JavierInternational Journal of Life Cycle Assessment (2017), 22 (3), 346-363CODEN: IJLCFF; ISSN:0948-3349. (Springer)Purpose: As a first step towards a consistent framework for both individual and comparative life cycle assessment (LCA) of hydrogen energy systems, this work performs a thorough literature review on the methodol. choices made in LCA studies of these energy systems. Choices affecting the LCA stages "goal and scope definition", "life cycle inventory anal." (LCI) and "life cycle impact assessment" (LCIA) are targeted. Methods: This review considers 97 scientific papers published until Dec. 2015, in which 509 original case studies of hydrogen energy systems are found. Based on the hydrogen prodn. process, these case studies are classified into three technol. categories: thermochem., electrochem. and biol. A subdivision based on the scope of the studies is also applied, thus distinguishing case studies addressing hydrogen prodn. only, hydrogen prodn. and use in mobility and hydrogen prodn. and use for power generation. Results and discussion: Most of the hydrogen energy systems apply cradle/gate-to-gate boundaries, while cradle/gate-to-grave boundaries are found mainly for hydrogen use in mobility. The functional unit is usually mass- or energy-based for cradle/gate-to-gate studies and travelled distance for cradle/gate-to-grave studies. Multifunctionality is addressed mainly through system expansion and, to a lesser extent, phys. allocation. Regarding LCI, scientific literature and life cycle databases are the main data sources for both background and foreground processes. Regarding LCIA, the most common impact categories evaluated are global warming and energy consumption through the IPCC and VDI methods, resp. The remaining indicators are often evaluated using the CML family methods. The level of agreement of these trends with the available FC-HyGuide guidelines for LCA of hydrogen energy systems depends on the specific methodol. aspect considered. Conclusions: This review on LCA of hydrogen energy systems succeeded in finding relevant trends in methodol. choices, esp. regarding the frequent use of system expansion and secondary data under prodn.-oriented attributional approaches. These trends are expected to facilitate methodol. decision making in future LCA studies of hydrogen energy systems. Furthermore, this review may provide a basis for the definition of a methodol. framework to harmonise the LCA results of hydrogen available so far in the literature.
- 3Rinawati, D. I.; Keeley, A. R.; Takeda, S.; Managi, S. A Systematic Review of Life Cycle Assessment of Hydrogen for Road Transport Use. Prog. Energy 2022, 4 (1), 012001 DOI: 10.1088/2516-1083/ac34e9There is no corresponding record for this reference.
- 4Rinawati, D. I.; Keeley, A. R.; Takeda, S.; Managi, S. Life-Cycle Assessment of Hydrogen Utilization in Power Generation: A Systematic Review of Technological and Methodological Choices. Front. Sustain. 2022, 3, 920876 DOI: 10.3389/frsus.2022.920876There is no corresponding record for this reference.
- 5Hydrogen Council. Hydrogen Decarbonization Pathways: A Life-Cycle Assessment. 2021. https://hydrogencouncil.com/en/hydrogen-decarbonization-pathways/ (last accessed 2024-01-12).There is no corresponding record for this reference.
- 6Bhandari, R.; Trudewind, C. A.; Zapp, P. Life Cycle Assessment of Hydrogen Production via Electrolysis – a Review. J. Clean. Prod. 2014, 85, 151– 163, DOI: 10.1016/j.jclepro.2013.07.048There is no corresponding record for this reference.
- 7Cetinkaya, E.; Dincer, I.; Naterer, G. F. Life Cycle Assessment of Various Hydrogen Production Methods. Int. J. Hydrogen Energ 2012, 37 (3), 2071– 2080, DOI: 10.1016/j.ijhydene.2011.10.0647Life cycle assessment of various hydrogen production methodsCetinkaya, E.; Dincer, I.; Naterer, G. F.International Journal of Hydrogen Energy (2012), 37 (3), 2071-2080CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)A comprehensive life cycle assessment (LCA) is reported for five methods of hydrogen prodn., namely steam reforming of natural gas, coal gasification, water electrolysis via wind and solar electrolysis, and thermochem. water splitting with a Cu-Cl cycle. Carbon dioxide equiv. emissions and energy equiv. of each method are quantified and compared. A case study is presented for a hydrogen fueling station in Toronto, Canada, and nearby hydrogen resources close to the fueling station. In terms of carbon dioxide equiv. emissions, thermochem. water splitting with the Cu-Cl cycle is found to be advantageous over the other methods, followed by wind and solar electrolysis. In terms of hydrogen prodn. capacities, natural gas steam reforming, coal gasification and thermochem. water splitting with the Cu-Cl cycle methods are found to be advantageous over the renewable energy methods.
- 8Lee, D.-Y.; Elgowainy, A.; Kotz, A.; Vijayagopal, R.; Marcinkoski, J. Life-Cycle Implications of Hydrogen Fuel Cell Electric Vehicle Technology for Medium- and Heavy-Duty Trucks. J. Power Sources 2018, 393, 217– 229, DOI: 10.1016/j.jpowsour.2018.05.0128Life-cycle implications of hydrogen fuel cell electric vehicle technology for medium- and heavy-duty trucksLee, Dong-Yeon; Elgowainy, Amgad; Kotz, Andrew; Vijayagopal, Ram; Marcinkoski, JasonJournal of Power Sources (2018), 393 (), 217-229CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)This study provides a comprehensive and up-to-date life-cycle comparison of hydrogen fuel cell elec. trucks (FCETs) and their conventional diesel counterparts in terms of energy use and air emissions, based on the ensemble of well-established methods, high-fidelity vehicle dynamic simulations, and real-world vehicle test data. For the centralized steam methane reforming (SMR) pathway, hydrogen FCETs reduce life-cycle or well-to-wheel (WTW) petroleum energy use by more than 98% compared to their diesel counterparts. The redn. in WTW air emissions for gaseous hydrogen (G.H2) FCETs ranges from 20 to 45% for greenhouse gases, 37-65% for VOC, 49-77% for CO, 62-83% for NOx, 19-43% for PM10, and 27-44% for PM2.5, depending on vehicle wt. classes and truck types. With the current U. S. av. electricity generation mix, FCETs tend to create more WTW SOx emissions than their diesel counterparts, mainly because of the upstream emissions related to electricity use for hydrogen compression/liquefaction. Compared to G. H2, liq. hydrogen (L.H2) FCETs generally provide smaller WTW emissions redns. For both G.H2 and L. H2 pathways for FCETs, because of electricity consumption for compression and liquefaction, spatio-temporal variations of electricity generation can affect the WTW results. FCETs retain the WTW emission redn. benefits, even when considering aggressive diesel engine efficiency improvement.
- 9Frank, E. D.; Elgowainy, A.; Reddi, K.; Bafana, A. Life-Cycle Analysis of Greenhouse Gas Emissions from Hydrogen Delivery: A Cost-Guided Analysis. Int. J. Hydrogen Energ 2021, 46 (43), 22670– 22683, DOI: 10.1016/j.ijhydene.2021.04.0789Life-cycle analysis of greenhouse gas emissions from hydrogen delivery: A cost-guided analysisFrank, Edward D.; Elgowainy, Amgad; Reddi, Krishna; Bafana, AdarshInternational Journal of Hydrogen Energy (2021), 46 (43), 22670-22683CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)The cost of hydrogen delivery for transportation accounts for most of the current H2 selling price; delivery also requires substantial amts. of energy. We developed harmonized techno-economic and life-cycle emissions models of current and future H2 prodn. and delivery pathways. Our techno-economic anal. of dispensed H2 costs guided our selection of pathways for the life-cycle anal. In this paper, we present the results of market expansion scenarios using existing capabilities (for example, those that use H2 from steam methane reforming, chlor-alkali, and natural gas liq. cracker plants), as well as results for future electrolysis plants that use nuclear, solar, and hydroelec. power. Redns. in greenhouse gas emissions for fuel cell elec. vehicles compared to conventional gasoline pathways vary from 40% redn. for fossil-derived H2 to 20-fold for clean H2. Supplemental tables with greenhouse gas emissions data for each step in the H2 pathways enable readers to evaluate addnl. scenarios.
- 10Paulot, F.; Paynter, D.; Naik, V.; Malyshev, S.; Menzel, R.; Horowitz, L. W. Global Modeling of Hydrogen Using GFDL-AM4.1: Sensitivity of Soil Removal and Radiative Forcing. Int. J. Hydrogen Energ 2021, 46 (24), 13446– 13460, DOI: 10.1016/j.ijhydene.2021.01.08810Global modeling of hydrogen using GFDL-AM4.1: Sensitivity of soil removal and radiative forcingPaulot, Fabien; Paynter, David; Naik, Vaishali; Malyshev, Sergey; Menzel, Raymond; Horowitz, Larry W.International Journal of Hydrogen Energy (2021), 46 (24), 13446-13460CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)Hydrogen (H2) was proposed as an alternative energy carrier to reduce the carbon footprint and assocd. radiative forcing of the current energy system. Here, we describe the representation of H2 in the GFDL-AM4.1 model including updated emission inventories and improved representation of H2 soil removal, the dominant sink of H2. The model best captures the overall distribution of surface H2, including regional contrasts between climate zones, when vd(H2) is modulated by soil moisture, temp., and soil carbon content. We est. that the soil removal of H2 increases with warming (2-4% per K), with large uncertainties stemming from different regional response of soil moisture and soil carbon. We est. that H2 causes an indirect radiative forcing of 0.84 mW m-2/(Tg(H2)yr-1) or 0.13 mW m-2 ppbv-1, primarily due to increasing CH4 lifetime and stratospheric water vapor prodn.
- 11Warwick, N. J.; Archibald, A. T.; Griffiths, P. T.; Keeble, J.; O’Connor, F. M.; Pyle, J. A.; Shine, K. P. Atmospheric Composition and Climate Impacts of a Future Hydrogen Economy. Atmos. Chem. Phys. 2023, 23 (20), 13451– 13467, DOI: 10.5194/acp-23-13451-202311Atmospheric composition and climate impacts of a future hydrogen economyWarwick, Nicola J.; Archibald, Alex T.; Griffiths, Paul T.; Keeble, James; O'Connor, Fiona M.; Pyle, John A.; Shine, Keith P.Atmospheric Chemistry and Physics (2023), 23 (20), 13451-13467CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)Hydrogen is expected to play a key role in the global energy transition to net zero emissions in many scenarios. However, fugitive emissions of hydrogen into the atm. during its prodn., storage, distribution and use could reduce the climate benefit and also have implications for air quality. Here, we explore the atm. compn. and climate impacts of increases in atm. hydrogen abundance using the UK Earth System Model (UKESM1) chem.-climate model. Increases in hydrogen result in increases in methane, tropospheric ozone and stratospheric water vapor, resulting in a pos. radiative forcing. However, some of the impacts of hydrogen leakage are partially offset by potential redns. in emissions of methane, carbon monoxide, nitrogen oxides and volatile org. compds. from the consumption of fossil fuels. We derive a refined methodol. for detg. indirect global warming potentials (GWPs) from parameters derived from steady-state simulations, which is applicable to both shorter-lived species and those with intermediate and longer lifetimes, such as hydrogen. Using this methodol., we det. a 100-yr global warming potential for hydrogen of 12 ± 6. Based on this GWP and hydrogen leakage rates of 1% and 10%, we find that hydrogen leakage offsets approx. 0.4% and 4% resp. of total equiv. CO2 emission redns. in our global hydrogen economy scenario. To maximise the benefit of hydrogen as an energy source, emissions assocd. with hydrogen leakage and emissions of the ozone precursor gases need to be minimised.
- 12Hauglustaine, D.; Paulot, F.; Collins, W.; Derwent, R.; Sand, M.; Boucher, O. Climate Benefit of a Future Hydrogen Economy. Commun. Earth Environ 2022, 3 (1), 295, DOI: 10.1038/s43247-022-00626-zThere is no corresponding record for this reference.
- 13Sand, M.; Skeie, R. B.; Sandstad, M.; Krishnan, S.; Myhre, G.; Bryant, H.; Derwent, R.; Hauglustaine, D.; Paulot, F.; Prather, M.; Stevenson, D. A Multi-Model Assessment of the Global Warming Potential of Hydrogen. Commun. Earth Environ. 2023, 4 (1), 203, DOI: 10.1038/s43247-023-00857-8There is no corresponding record for this reference.
- 14Hauglustaine, D. A.; Ehhalt, D. H. A Three-dimensional Model of Molecular Hydrogen in the Troposphere. J. Geophys. Res.: Atmos. 2002, 107 (D17), ACH 4-1– ACH 4-16, DOI: 10.1029/2001JD001156There is no corresponding record for this reference.
- 15Field, R. A.; Derwent, R. G. Global Warming Consequences of Replacing Natural Gas with Hydrogen in the Domestic Energy Sectors of Future Low-Carbon Economies in the United Kingdom and the United States of America. Int. J. Hydrogen Energ 2021, 46 (58), 30190– 30203, DOI: 10.1016/j.ijhydene.2021.06.12015Global warming consequences of replacing natural gas with hydrogen in the domestic energy sectors of future low-carbon economies in the United Kingdom and the United States of AmericaField, R. A.; Derwent, R. G.International Journal of Hydrogen Energy (2021), 46 (58), 30190-30203CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)Hydrogen has a potentially important future role as a replacement for natural gas in the domestic sector in a zero-carbon economy for heating homes and cooking. To assess this potential, an understanding is required of the global warming potentials (GWPs) of methane and hydrogen and of the leakage rates of the natural gas distribution system and that of a hydrogen system that would replace it. The GWPs of methane and hydrogen were estd. using a global chem.-transport model as 29.2 ± 8 and 3.3 ± 1.4, resp., over a 100-yr time horizon. The current natural gas leakage rates from the distribution system were estd. for the UK by the ethane tracer method to be ∼0.64 Tg CH4/yr (2.3%) and for the US by literature review to be of the order of 0.69-2.9 Tg CH4/yr (0.5-2.1%). On this basis, with the inclusion of carbon dioxide emissions from combustion, replacing natural gas with green hydrogen in the domestic sectors of both countries should reduce substantially the global warming consequences of domestic sector energy use both in the UK and in the US, provided care is taken to reduce hydrogen leakage to a min. A perfectly sealed zero-carbon green hydrogen distribution system would save the entire 76 million tonnes CO2 equivalent per yr in the UK.
- 16Derwent, R. G.; Stevenson, D. S.; Utembe, S. R.; Jenkin, M. E.; Khan, A. H.; Shallcross, D. E. Global Modelling Studies of Hydrogen and Its Isotopomers Using STOCHEM-CRI: Likely Radiative Forcing Consequences of a Future Hydrogen Economy. Int. J. Hydrogen Energ 2020, 45 (15), 9211– 9221, DOI: 10.1016/j.ijhydene.2020.01.12516Global modelling studies of hydrogen and its isotopomers using STOCHEM-CRI: Likely radiative forcing consequences of a future hydrogen economyDerwent, Richard G.; Stevenson, David S.; Utembe, Steven R.; Jenkin, Michael E.; Khan, Anwar H.; Shallcross, Dudley E.International Journal of Hydrogen Energy (2020), 45 (15), 9211-9221CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)A global chem.-transport model was employed to describe the global sources and sinks of hydrogen (H2) and its isotopomer (HD). The model is able to satisfactorily describe the obsd. tropospheric distributions of H2 and HD and deliver budgets and turnovers which agree with literature studies. We than go on to quantify the methane and ozone responses to emission pulses of hydrogen and their likely radiative forcing consequences. These radiative forcing consequences were expressed on a 1 Tg basis and integrated over a hundred-year time horizon. When compared to the consequences of a 1 Tg emission pulse of carbon dioxide, 1 Tg of hydrogen causes 5 ± 1 times as much time-integrated radiative forcing over a hundred-year time horizon. That is to say, hydrogen has a global warming potential (GWP) of 5 ± 1 over a hundred-year time horizon. The global warming consequences of a hydrogen-based low-carbon energy system therefore depend critically on the hydrogen leakage rate. If the leakage of hydrogen from all stages in the prodn., distribution, storage and utilization of hydrogen is efficiently curtailed, then hydrogen-based energy systems appear to be an attractive proposition in providing a future replacement for fossil-fuel based energy systems.
- 17Derwent, R.; Simmonds, P.; O’Doherty, S.; Manning, A.; Collins, W.; Stevenson, D. Global Environmental Impacts of the Hydrogen Economy. Int. J. Nucl. Hydrogen Prod Appl. 2006, 1 (1), 57, DOI: 10.1504/IJNHPA.2006.009869There is no corresponding record for this reference.
- 18Derwent, R. G.; Collins, W. J.; Johnson, C. E.; Stevenson, D. S. Transient Behaviour of Tropospheric Ozone Precursors in a Global 3-D CTM and Their Indirect Greenhouse Effects. Climatic Change 2001, 49 (4), 463– 487, DOI: 10.1023/A:101064891365518Transient behaviour of tropospheric ozone precursors in a global 3-D CTM and their indirect greenhouse effectsDerwent, R. G.; Collins, W. J.; Johnson, C. E.; Stevenson, D. S.Climatic Change (2001), 49 (4), 463-487CODEN: CLCHDX; ISSN:0165-0009. (Kluwer Academic Publishers)The global three-dimensional Lagrangian chem.-transport model STOCHEM has been used to follow the changes in the tropospheric distributions of the two major radiatively-active trace gases, methane and tropospheric ozone, following the emission of pulses of the short-lived tropospheric ozone precursor species, methane, carbon monoxide, NOx and hydrogen. The radiative impacts of NOx emissions were dependent on the location chosen for the emission pulse, whether at the surface or in the upper troposphere or whether in the northern or southern hemispheres. Global warming potentials were derived for each of the short-lived tropospheric ozone precursor species by integrating the methane and tropospheric ozone responses over a 100-yr time horizon. Indirect radiative forcing due to methane and tropospheric ozone changes appear to be significant for all of the tropospheric ozone precursor species studied. Whereas the radiative forcing from methane changes is likely to be dominated by methane emissions, that from tropospheric ozone changes is controlled by all the tropospheric ozone precursor gases, particularly NOx emissions. The indirect radiative forcing impacts of tropospheric ozone changes may be large enough such that ozone precursors should be considered in the basket of trace gases through which policy-makers aim to combat global climate change.
- 19Prather, M. J. An Environmental Experiment with H2?. Science 2003, 302 (5645), 581– 582, DOI: 10.1126/science.109106019Atmospheric science: An environmental experiment with H2?Prather, Michael J.Science (Washington, DC, United States) (2003), 302 (5645), 581-582CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A review of the environmental consequences of a H2 fuel economy, including leaks that would cause large increases in atm. H2, affecting stratospheric water vapor, temp. and O3; natural and anthropogenic sources of H2; atm. and soil sinks of H2; indirect greenhouse gas effects; indirect increases of CH4; and NOx redns.
- 20Schultz, M. G.; Diehl, T.; Brasseur, G. P.; Zittel, W. Air Pollution and Climate-Forcing Impacts of a Global Hydrogen Economy. Science 2003, 302 (5645), 624– 627, DOI: 10.1126/science.108952720Air pollution and climate-forcing impacts of a global hydrogen economySchultz, Martin G.; Diehl, Thomas; Brasseur, Guy P.; Zittel, WernerScience (Washington, DC, United States) (2003), 302 (5645), 624-627CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)If today's surface traffic fleet were powered entirely by H fuel cell technol., anthropogenic emissions of the ozone precursors NOx and CO could be reduced by ≤50%, leading to significant improvements in air quality throughout the Northern Hemisphere. Model simulations of such a scenario predict a decrease in global OH and an increased lifetime of CH4, caused primarily by the redn. of the NOx emissions. The sign of the change in climate forcing caused by CO2 and CH4 depends on the technol. used to generate the H2. A possible rise in atm. H concns. is unlikely to cause significant perturbations of the climate system.
- 21Warwick, N. J.; Bekki, S.; Nisbet, E. G.; Pyle, J. A. Impact of a Hydrogen Economy on the Stratosphere and Troposphere Studied in a 2-D Model. Geophys. Res. Lett. 2004, 31 (5), L05107 DOI: 10.1029/2003GL01922421Impact of a hydrogen economy on the stratosphere and troposphere studied in a 2-D modelWarwick, N. J.; Bekki, S.; Nisbet, E. G.; Pyle, J. A.Geophysical Research Letters (2004), 31 (5), L05107/1-L05107/4CODEN: GPRLAJ; ISSN:0094-8276. (American Geophysical Union)A switch from a fossil fuel to a hydrogen-based energy system could cause significant changes in the magnitude and compn. of anthropogenic emissions. Model simulations suggest the most significant impact of these emission changes would occur in the troposphere, affecting OH. This impact is dependent upon the magnitude and nature of trade-offs in changing fossil fuel use. In the stratosphere, changes in water vapor resulting from expected increases in surface mol. hydrogen emissions via leaks occurring during prodn., transport, and storage, are found to be significantly smaller than previous ests. We conclude that the expected increase in mol. hydrogen emissions is unlikely to have a substantial impact on stratospheric ozone, certainly much smaller than the ozone changes obsd. in the last two decades.
- 22Colella, W. G.; Jacobson, M. Z.; Golden, D. M. Switching to a U.S. Hydrogen Fuel Cell Vehicle Fleet: The Resultant Change in Emissions, Energy Use, and Greenhouse Gases. J. Power Sources 2005, 150, 150– 181, DOI: 10.1016/j.jpowsour.2005.05.09222Switching to a U.S. hydrogen fuel cell vehicle fleet: The resultant change in emissions, energy use, and greenhouse gasesColella, W. G.; Jacobson, M. Z.; Golden, D. M.Journal of Power Sources (2005), 150 (), 150-181CODEN: JPSODZ; ISSN:0378-7753. (Elsevier B.V.)This study examines the potential change in primary emissions and energy use as a result of replacing the current U.S. fleet of fossil-fuel on-road vehicles (FFOV) with hybrid elec. fossil fuel vehicles or hydrogen fuel cell vehicles (HFCV). Emissions and energy usage are analyzed for three different HFCV scenarios, with hydrogen produced by (a) steam reforming of natural gas, (b) electrolysis powered by wind energy, and (c) coal gasification. With the U.S. EPA National Emission Inventory as the baseline, other emission inventories are created using a life cycle assessment of alternative fuel supply chains. For a range of reasonable HFCV efficiencies and methods of producing hydrogen, we find that the replacement of FFOV with HFCV significantly reduces emission assocd. with air pollution, compared even with a switch to hybrids. All HFCV scenarios decrease net air pollution emission, including nitrogen oxides, volatile org. compds., particulate matter, ammonia, and carbon monoxide. These redns. are achieved with hydrogen prodn. from either a fossil fuel source such as natural gas or a renewable source such as wind. Furthermore, replacing FFOV with hybrids or HFCV with hydrogen derived from natural gas, wind or coal may reduce the global warming impact of greenhouse gases and particles (measured in carbon dioxide equiv. emission) by 6, 14, 23, and 1%, resp. Finally, even if HFCV are fueled by a fossil fuel such as natural gas, if no carbon is sequestered during hydrogen prodn., and 1% of methane in the feedstock gas is leaked to the environment, natural gas HFCV still may achieve a significant redn. in greenhouse gas and air pollution emission over FFOV.
- 23Wuebbles, D. J. Evaluation of the Potential Environmental Impacts from Large-Scale Use and Production of Hydrogen in Energy and Transportation Applications. 2008. https://digital.library.unt.edu/ark:/67531/metadc841210/ (last accessed 2024-01-12).There is no corresponding record for this reference.
- 24Frazer-Nash Consultancy. Fugitive Hydrogen Emissions in a Future Hydrogen Economy. 2022. https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/1067137/fugitive-hydrogen-emissions-future-hydrogen-economy.pdf (last accessed 2024-01-12).There is no corresponding record for this reference.
- 25Arrigoni, A.; Bravo, D. L. Hydrogen Emissions from a Hydrogen Economy and Their Potential Global Warming Impact. 2022; OP KJ-NA-31-188-EN-N. DOI: 10.2760/065589There is no corresponding record for this reference.
- 26Cooper, J.; Dubey, L.; Bakkaloglu, S.; Hawkes, A. Hydrogen Emissions from the Hydrogen Value Chain-Emissions Profile and Impact to Global Warming. Sci. Total Environ. 2022, 830, 154624 DOI: 10.1016/j.scitotenv.2022.15462426Hydrogen emissions from the hydrogen value chain-emissions profile and impact to global warmingCooper, Jasmin; Dubey, Luke; Bakkaloglu, Semra; Hawkes, AdamScience of the Total Environment (2022), 830 (), 154624CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)Future energy systems could rely on hydrogen (H2) to achieve decarbonisation and net-zero goals. In a similar energy landscape to natural gas, H2 emissions occur along the supply chain. It has been studied how current gas infrastructure can support H2, but there is little known about how H2 emissions affect global warming as an indirect greenhouse gas. In this work, we have estd. for the first time the potential emission profiles (g CO2eq/MJ H2,HHV) of H2 supply chains, and found that the emission rates of H2 from H2 supply chains and methane from natural gas supply are comparable, but the impact on global warming is much lower based on current ests. This study also demonstrates the crit. importance of establishing mobile H2 emission monitoring and reducing the uncertainty of short-lived H2 climate forcing so as to clearly address H2 emissions for net-zero strategies.
- 27Fan, Z.; Sheerazi, H.; Bhardwaj, A.; Corbeau, A.-S.; Longobardi, K.; Castañeda, A.; Merz, A.-K.; Woodall, C. M.; Agrawal, M.; Orozco-Sanchez, S.; Friedmann, J. Hydrogen Leakage: A Potential Risk for the Hydrogen Economy; Center on Global Energy Policy. 2022. https://www.energypolicy.columbia.edu/publications/hydrogen-leakage-potential-risk-hydrogen-economy/ (last accessed 2024-01-12).There is no corresponding record for this reference.
- 28Esquivel-Elizondo, S.; Hormaza Mejia, A.; Sun, T.; Shrestha, E.; Hamburg, S. P.; Ocko, I. B. Wide Range in Estimates of Hydrogen Emissions from Infrastructure. Front. Energy Res. 2023, 11, 01– 08, DOI: 10.3389/fenrg.2023.1207208There is no corresponding record for this reference.
- 29Alvarez, R. A.; Zavala-Araiza, D.; Lyon, D. R.; Allen, D. T.; Barkley, Z. R.; Brandt, A. R.; Davis, K. J.; Herndon, S. C.; Jacob, D. J.; Karion, A.; Kort, E. A.; Lamb, B. K.; Lauvaux, T.; Maasakkers, J. D.; Marchese, A. J.; Omara, M.; Pacala, S. W.; Peischl, J.; Robinson, A. L.; Shepson, P. B.; Sweeney, C.; Townsend-Small, A.; Wofsy, S. C.; Hamburg, S. P. Assessment of Methane Emissions from the U.S. Oil and Gas Supply Chain. Science 2018, 361 (6398), 186– 188, DOI: 10.1126/science.aar720429Assessment of methane emissions from the U.S. oil and gas supply chainAlvarez, Ramon A.; Zavala-Araiza, Daniel; Lyon, David R.; Allen, David T.; Barkley, Zachary R.; Brandt, Adam R.; Davis, Kenneth J.; Herndon, Scott C.; Jacob, Daniel J.; Karion, Anna; Kort, Eric A.; Lamb, Brian K.; Lauvaux, Thomas; Maasakkers, Joannes D.; Marchese, Anthony J.; Omara, Mark; Pacala, Stephen W.; Peischl, Jeff; Robinson, Allen L.; Shepson, Paul B.; Sweeney, Colm; Townsend-Small, Amy; Wofsy, Steven C.; Hamburg, Steven P.Science (Washington, DC, United States) (2018), 361 (6398), 186-188CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)Considerable amts. of the greenhouse gas methane leak from the U.S. oil and natural gas supply chain. Alvarez et al. reassessed the magnitude of this leakage and found that in 2015, supply chain emissions were ∼60% higher than the U.S. Environmental Protection Agency inventory est. They suggest that this discrepancy exists because current inventory methods miss emissions that occur during abnormal operating conditions. These data, and the methodol. used to obtain them, could improve and verify international inventories of greenhouse gases and provide a better understanding of mitigation efforts outlined by the Paris Agreement.
- 30Shen, L.; Gautam, R.; Omara, M.; Zavala-Araiza, D.; Maasakkers, J. D.; Scarpelli, T. R.; Lorente, A.; Lyon, D.; Sheng, J.; Varon, D. J.; Nesser, H.; Qu, Z.; Lu, X.; Sulprizio, M. P.; Hamburg, S. P.; Jacob, D. J. Satellite Quantification of Oil and Natural Gas Methane Emissions in the US and Canada Including Contributions from Individual Basins. Atmos. Chem. Phys. 2022, 22 (17), 11203– 11215, DOI: 10.5194/acp-22-11203-202230Satellite quantification of oil and natural gas methane emissions in the US and Canada including contributions from individual basinsShen, Lu; Gautam, Ritesh; Omara, Mark; Zavala-Araiza, Daniel; Maasakkers, Joannes D.; Scarpelli, Tia R.; Lorente, Alba; Lyon, David; Sheng, Jianxiong; Varon, Daniel J.; Nesser, Hannah; Qu, Zhen; Lu, Xiao; Sulprizio, Melissa P.; Hamburg, Steven P.; Jacob, Daniel J.Atmospheric Chemistry and Physics (2022), 22 (17), 11203-11215CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)We use satellite methane observations from the Tropospheric Monitoring Instrument (TROPOMI), for May 2018 to Feb. 2020, to quantify methane emissions from individual oil and natural gas (O/G) basins in the US and Canada using a high-resoln. (∼25 km) atm. inverse anal. Our satellite-derived emission ests. show good consistency with in situ field measurements (R = 0.96) in 14 O/G basins distributed across the US and Canada. Aggregating our results to the national scale, we obtain O/G-related methane emission ests. of 12.6 ± 2.1 Tg a-1 for the US and 2.2 ± 0.6 Tg a-1 for Canada, 80% and 40%, resp., higher than the national inventories reported to the United Nations. About 70% of the discrepancy in the US Environmental Protection Agency (EPA) inventory can be attributed to five O/G basins, the Permian, Haynesville, Anadarko, Eagle Ford, and Barnett basins, which in total account for 40% of US emissions. We show more generally that our TROPOMI inversion framework can quantify methane emissions exceeding 0.2-0.5 Tg a-1 from individual O/G basins, thus providing an effective tool for monitoring methane emissions from large O/G basins globally.
- 31Foulds, A.; Allen, G.; Shaw, J. T.; Bateson, P.; Barker, P. A.; Huang, L.; Pitt, J. R.; Lee, J. D.; Wilde, S. E.; Dominutti, P.; Purvis, R. M.; Lowry, D.; France, J. L.; Fisher, R. E.; Fiehn, A.; Pühl, M.; Bauguitte, S. J. B.; Conley, S. A.; Smith, M. L.; Lachlan-Cope, T.; Pisso, I.; Schwietzke, S. Quantification and Assessment of Methane Emissions from Offshore Oil and Gas Facilities on the Norwegian Continental Shelf. Atmos Chem. Phys. 2022, 22 (7), 4303– 4322, DOI: 10.5194/acp-22-4303-202231Quantification and assessment of methane emissions from offshore oil and gas facilities on the Norwegian continental shelfFoulds, Amy; Allen, Grant; Shaw, Jacob T.; Bateson, Prudence; Barker, Patrick A.; Huang, Langwen; Pitt, Joseph R.; Lee, James D.; Wilde, Shona E.; Dominutti, Pamela; Purvis, Ruth M.; Lowry, David; France, James L.; Fisher, Rebecca E.; Fiehn, Alina; Puhl, Magdalena; Bauguitte, Stephane J. B.; Conley, Stephen A.; Smith, Mackenzie L.; Lachlan-Cope, Tom; Pisso, Ignacio; Schwietzke, StefanAtmospheric Chemistry and Physics (2022), 22 (7), 4303-4322CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)The oil and gas (O&G) sector is a significant source of methane (CH4) emissions. Quantifying these emissions remains challenging, with many studies highlighting discrepancies between measurements and inventory-based ests. In this study, we present CH4 emission fluxes from 21 offshore O&G facilities collected in 10 O&G fields over two regions of the Norwegian continental shelf in 2019. Emissions of CH4 derived from measurements during 13 aircraft surveys were found to range from 2.6 to 1200 t yr-1 (with a mean of 211 t yr-1 across all 21 facilities). Comparing this with aggregated operator-reported facility emissions for 2019, we found excellent agreement (within 1σ uncertainty), with mean aircraft-measured fluxes only 16% lower than those reported by operators. We also compared aircraft-derived fluxes with facility fluxes extd. from a global gridded fossil fuel CH4 emission inventory compiled for 2016. We found that the measured emissions were 42% larger than the inventory for the area covered by this study, for the 21 facilities surveyed (in aggregate). We interpret this large discrepancy not to reflect a systematic error in the operator-reported emissions, which agree with measurements, but rather the representativity of the global inventory due to the methodol. used to construct it and the fact that the inventory was compiled for 2016 (and thus not representative of emissions in 2019). This highlights the need for timely and up-to-date inventories for use in research and policy. The variable nature of CH4 emissions from individual facilities requires knowledge of facility operational status during measurements for data to be useful in prioritising targeted emission mitigation solns. Future surveys of individual facilities would benefit from knowledge of facility operational status over time. Field-specific aggregated emissions (and uncertainty statistics), as presented here for the Norwegian Sea, can be meaningfully estd. from intensive aircraft surveys. However, field-specific ests. cannot be reliably extrapolated to other prodn. fields without their own tailored surveys, which would need to capture a range of facility designs, oil and gas prodn. vols., and facility ages. For year-on-year comparison to annually updated inventories and regulatory emission reporting, analogous annual surveys would be needed for meaningful top-down validation. In summary, this study demonstrates the importance and accuracy of detailed, facility-level emission accounting and reporting by operators and the use of airborne measurement approaches to validate bottom-up accounting.
- 32MacKay, K.; Lavoie, M.; Bourlon, E.; Atherton, E.; O’Connell, E.; Baillie, J.; Fougère, C.; Risk, D. Methane Emissions from Upstream Oil and Gas Production in Canada Are Underestimated. Sci. Rep-uk 2021, 11 (1), 8041, DOI: 10.1038/s41598-021-87610-3There is no corresponding record for this reference.
- 33Chen, Y.; Sherwin, E. D.; Berman, E. S. F.; Jones, B. B.; Gordon, M. P.; Wetherley, E. B.; Kort, E. A.; Brandt, A. R. Quantifying Regional Methane Emissions in the New Mexico Permian Basin with a Comprehensive Aerial Survey. Environ. Sci. Technol. 2022, 56 (7), 4317– 4323, DOI: 10.1021/acs.est.1c0645833Quantifying Regional Methane Emissions in the New Mexico Permian Basin with a Comprehensive Aerial SurveyChen, Yuanlei; Sherwin, Evan D.; Berman, Elena S. F.; Jones, Brian B.; Gordon, Matthew P.; Wetherley, Erin B.; Kort, Eric A.; Brandt, Adam R.Environmental Science & Technology (2022), 56 (7), 4317-4323CODEN: ESTHAG; ISSN:1520-5851. (American Chemical Society)Limiting emissions of climate-warming methane from oil and gas (O&G) is a major opportunity for short-term climate benefits. We deploy a basin-wide airborne survey of O&G extn. and transportation activities in the New Mexico Permian Basin, spanning 35 923 km2, 26 292 active wells, and over 15 000 km of natural gas pipelines using an independently validated hyperspectral methane point source detection and quantification system. The airborne survey repeatedly visited over 90% of the active wells in the survey region throughout Oct. 2018 to Jan. 2020, totaling approx. 98 000 well site visits. We est. total O&G methane emissions in this area at 194 (+72/-68, 95% CI) metric tonnes per h (t/h), or 9.4% (+3.5%/-3.3%) of gross gas prodn. 50% of obsd. emissions come from large emission sources with persistence-averaged emission rates over 308 kg/h. The fact that a large sample size is required to characterize the heavy tail of the distribution emphasizes the importance of capturing low-probability, high-consequence events through basin-wide surveys when estg. regional O&G methane emissions.
- 34Howarth, R. W.; Jacobson, M. Z. How Green Is Blue Hydrogen?. Energy Sci. Eng. 2021, 9, 1676– 1687, DOI: 10.1002/ese3.95634How green is blue hydrogen?Howarth, Robert W.; Jacobson, Mark Z.Energy Science & Engineering (2021), 9 (10), 1676-1687CODEN: ESENGX; ISSN:2050-0505. (John Wiley & Sons Ltd.)A review. Hydrogen is often viewed as an important energy carrier in a future decarbonized world. Currently, most hydrogen is produced by steam reforming of methane in natural gas ("gray hydrogen"), with high carbon dioxide emissions. Increasingly, many propose using carbon capture and storage to reduce these emissions, producing so-called "blue hydrogen," frequently promoted as low emissions. We undertake the first effort in a peer-reviewed paper to examine the lifecycle greenhouse gas emissions of blue hydrogen accounting for emissions of both carbon dioxide and unburned fugitive methane. Far from being low carbon, greenhouse gas emissions from the prodn. of blue hydrogen are quite high, particularly due to the release of fugitive methane. For our default assumptions (3.5% emission rate of methane from natural gas and a 20-yr global warming potential), total carbon dioxide equiv. emissions for blue hydrogen are only 9%-12% less than for gray hydrogen. While carbon dioxide emissions are lower, fugitive methane emissions for blue hydrogen are higher than for gray hydrogen because of an increased use of natural gas to power the carbon capture. Perhaps surprisingly, the greenhouse gas footprint of blue hydrogen is more than 20% greater than burning natural gas or coal for heat and some 60% greater than burning diesel oil for heat, again with our default assumptions. In a sensitivity anal. in which the methane emission rate from natural gas is reduced to a low value of 1.54%, greenhouse gas emissions from blue hydrogen are still greater than from simply burning natural gas, and are only 18%-25% less than for gray hydrogen. Our anal. assumes that captured carbon dioxide can be stored indefinitely, an optimistic and unproven assumption. Even if true though, the use of blue hydrogen appears difficult to justify on climate grounds.
- 35Stocks, M.; Fazeli, R.; Hughes, L.; Beck, F. J. Global Emissions Implications from Co-Combusting Ammonia in Coal Fired Power Stations: An Analysis of the Japan-Australia Supply Chain. J. Clean. Prod. 2022, 336, 130092 DOI: 10.1016/j.jclepro.2021.130092There is no corresponding record for this reference.
- 36Ocko, I. B.; Hamburg, S. P. Climate Consequences of Hydrogen Emissions. Atmos. Chem. Phys. 2022, 22, 9349– 9368, DOI: 10.5194/acp-22-9349-202236Climate consequences of hydrogen emissionsOcko, Ilissa B.; Hamburg, Steven P.Atmospheric Chemistry and Physics (2022), 22 (14), 9349-9368CODEN: ACPTCE; ISSN:1680-7324. (Copernicus Publications)Given the urgency to decarbonize global energy systems, governments and industry are moving ahead with efforts to increase deployment of hydrogen technologies, infrastructure, and applications at an unprecedented pace, including USD billions in national incentives and direct investments. While zero- and low-carbon hydrogen hold great promise to help solve some of the world's most pressing energy challenges, hydrogen is also an indirect greenhouse gas whose warming impact is both widely overlooked and underestimated. This is largely because hydrogen's atm. warming effects are short-lived - lasting only a couple decades - but std. methods for characterizing climate impacts of gases consider only the long-term effect from a one-time pulse of emissions. For gases whose impacts are short-lived, like hydrogen, this long-term framing masks a much stronger warming potency in the near to medium term. This is of concern because hydrogen is a small mol. known to easily leak into the atm., and the total amt. of emissions (e.g., leakage, venting, and purging) from existing hydrogen systems is unknown. Therefore, the effectiveness of hydrogen as a decarbonization strategy, esp. over timescales of several decades, remains unclear. This paper evaluates the climate consequences of hydrogen emissions over all timescales by employing already published data to assess its potency as a climate forcer, evaluate the net warming impacts from replacing fossil fuel technologies with their clean hydrogen alternatives, and est. temp. responses to projected levels of hydrogen demand. We use the std. global warming potential metric, given its acceptance to stakeholders, and incorporate newly published equations that more fully capture hydrogen's several indirect effects, but we consider the effects of const. rather than pulse emissions over multiple time horizons. We account for a plausible range of hydrogen emission rates and include methane emissions when hydrogen is produced via natural gas with carbon capture, usage, and storage (CCUS) ("blue" hydrogen) as opposed to renewables and water ("green" hydrogen). For the first time, we show the strong timescale dependence when evaluating the climate change mitigation potential of clean hydrogen alternatives, with the emission rate detg. the scale of climate benefits or disbenefits. For example, green hydrogen applications with higher-end emission rates (10%) may only cut climate impacts from fossil fuel technologies in half over the first 2 decades, which is far from the common perception that green hydrogen energy systems are climate neutral. However, over a 100-yr period, climate impacts could be reduced by around 80%. On the other hand, lower-end emissions (1%) could yield limited impacts on the climate over all timescales. For blue hydrogen, assocd. methane emissions can make hydrogen applications worse for the climate than fossil fuel technologies for several decades if emissions are high for both gases; however, blue hydrogen yields climate benefits over a 100-yr period. While more work is needed to evaluate the warming impact of hydrogen emissions for specific end-use cases and value-chain pathways, it is clear that hydrogen emissions matter for the climate and warrant further attention from scientists, industry, and governments. This is crit. to informing where and how to deploy hydrogen effectively in the emerging decarbonized global economy.
- 37Bertagni, M. B.; Pacala, S. W.; Paulot, F.; Porporato, A. Risk of the Hydrogen Economy for Atmospheric Methane. Nat. Commun. 2022, 13 (1), 7706, DOI: 10.1038/s41467-022-35419-737Risk of the hydrogen economy for atmospheric methaneBertagni, Matteo B.; Pacala, Stephen W.; Paulot, Fabien; Porporato, AmilcareNature Communications (2022), 13 (1), 7706CODEN: NCAOBW; ISSN:2041-1723. (Nature Portfolio)Hydrogen (H2) is expected to play a crucial role in reducing greenhouse gas emissions. However, hydrogen losses to the atm. impact atm. chem., including pos. feedback on methane (CH4), the second most important greenhouse gas. Here we investigate through a minimalist model the response of atm. methane to fossil fuel displacement by hydrogen. We find that CH4 concn. may increase or decrease depending on the amt. of hydrogen lost to the atm. and the methane emissions assocd. with hydrogen prodn. Green H2 can mitigate atm. methane if hydrogen losses throughout the value chain are below 9 ± 3%. Blue H2 can reduce methane emissions only if methane losses are below 1%. We address and discuss the main uncertainties in our results and the implications for the decarbonization of the energy sector.
- 38Bauer, C.; Treyer, K.; Antonini, C.; Bergerson, J.; Gazzani, M.; Gencer, E.; Gibbins, J.; Mazzotti, M.; McCoy, S. T.; McKenna, R.; Pietzcker, R.; Ravikumar, A. P.; Romano, M. C.; Ueckerdt, F.; Vente, J.; van der Spek, M. On the Climate Impacts of Blue Hydrogen Production. Sustainable Energy Fuels 2021, 6 (1), 66– 75, DOI: 10.1039/D1SE01508GThere is no corresponding record for this reference.
- 39Ricks, W.; Xu, Q.; Jenkins, J. D. Minimizing Emissions from Grid-Based Hydrogen Production in the United States. Environ. Res. Lett. 2023, 18 (1), 014025 DOI: 10.1088/1748-9326/acacb5There is no corresponding record for this reference.
- 40Alvarez, R. A.; Pacala, S. W.; Winebrake, J. J.; Chameides, W. L.; Hamburg, S. P. Greater Focus Needed on Methane Leakage from Natural Gas Infrastructure. Proc. National Acad. Sci. 2012, 109 (17), 6435– 6440, DOI: 10.1073/pnas.120240710940Greater focus needed on methane leakage from natural gas infrastructureAlvarez, Ramon A.; Pacala, Stephen W.; Winebrake, James J.; Chameides, William L.; Hamburg, Steven P.Proceedings of the National Academy of Sciences of the United States of America (2012), 109 (17), 6435-6440, S6435/1-S6435/7CODEN: PNASA6; ISSN:0027-8424. (National Academy of Sciences)Natural gas is seen by many as the future of American energy: a fuel that can provide energy independence and reduce greenhouse gas emissions in the process. However, there has also been confusion about the climate implications of increased use of natural gas for elec. power and transportation. We propose and illustrate the use of technol. warming potentials as a robust and transparent way to compare the cumulative radiative forcing created by alternative technologies fueled by natural gas and oil or coal by using the best available ests. of greenhouse gas emissions from each fuel cycle (i.e., prodn., transportation and use). We find that a shift to compressed natural gas vehicles from gasoline or diesel vehicles leads to greater radiative forcing of the climate for 80 or 280 yr, resp., before beginning to produce benefits. Compressed natural gas vehicles could produce climate benefits on all time frames if the well-to-wheels CH4 leakage were capped at a level 45-70% below current ests. By contrast, using natural gas instead of coal for elec. power plants can reduce radiative forcing immediately, and reducing CH4 losses from the prodn. and transportation of natural gas would produce even greater benefits. There is a need for the natural gas industry and science community to help obtain better emissions data and for increased efforts to reduce methane leakage in order to minimize the climate footprint of natural gas.
- 41Ocko, I. B.; Hamburg, S. P. Climate Impacts of Hydropower: Enormous Differences among Facilities and over Time. Environ. Sci. Technol. 2019, 53 (23), 14070– 14082, DOI: 10.1021/acs.est.9b0508341Climate Impacts of Hydropower: Enormous Differences among Facilities and over TimeOcko, Ilissa B.; Hamburg, Steven P.Environmental Science & Technology (2019), 53 (23), 14070-14082CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)To stabilize climate, humans must rapidly displace fossil fuels with clean energy technologies. Currently, hydropower dominates renewable electricity generation, accounting for 2/3 globally; it is expected to grow at least 45% by 2040. While it is broadly assumed that hydropower facilities emit greenhouse gases on par with wind, there is mounting evidence that emissions can be considerably greater, with some facilities even on par with fossil fuels. However, analyses of climate impacts of hydropower facilities have been simplistic, emphasizing aggregated 100-yr impacts from a one-year emissions pulse. Such analyses mask near-term impacts of CH4 emissions central to many current policy regimes, tending to omit CO2 emissions assocd. with initial facility development, and not considering the effect of atm. gas accumulation over time. An analytic approach which addresses these issues was developed. By analyzing climate impacts of sustained hydropower emissions over time, the authors detd. there are enormous differences in climate impacts among facilities and over time. If minimizing climate impacts are not a priority for design and construction of new hydropower facilities, it could lead to limited or even no climate benefits.
- 42Tromp, T. K.; Shia, R.-L.; Allen, M.; Eiler, J. M.; Yung, Y. L. Potential Environmental Impact of a Hydrogen Economy on the Stratosphere. Science 2003, 300 (5626), 1740– 1742, DOI: 10.1126/science.108516942Potential Environmental Impact of a Hydrogen Economy on the StratosphereTromp, Tracey K.; Shia, Run-Lie; Allen, Mark; Eiler, John M.; Yung, Y. L.Science (Washington, DC, United States) (2003), 300 (5626), 1740-1742CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)The widespread use of hydrogen fuel cells could have hitherto unknown environmental impacts due to unintended emissions of mol. hydrogen, including an increase in the abundance of water vapor in the stratosphere (plausibly by as much as ∼1 part per million by vol.). This would cause stratospheric cooling, enhancement of the heterogeneous chem. that destroys ozone, an increase in noctilucent clouds, and changes in tropospheric chem. and atm.-biosphere interactions.
- 43Jacobson, M. Z.; Colella, W. G.; Golden, D. M. Cleaning the Air and Improving Health with Hydrogen Fuel-Cell Vehicles. Science 2005, 308 (5730), 1901– 1905, DOI: 10.1126/science.110915743Cleaning the Air and Improving Health with Hydrogen Fuel-Cell VehiclesJacobson, M. Z.; Colella, W. G.; Golden, D. M.Science (Washington, DC, United States) (2005), 308 (5730), 1901-1905CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)A review. Converting all U.S. onroad vehicles to hydrogen fuel-cell vehicles (HFCVs) may improve air quality, health, and climate significantly, whether the hydrogen is produced by steam reforming of natural gas, wind electrolysis, or coal gasification. Most benefits would result from eliminating current vehicle exhaust. Wind and natural gas HFCVs offer the greatest potential health benefits and could save 3700 to 6400 U.S. lives annually. Wind HFCVs should benefit climate most. An all-HFCV fleet would hardly affect tropospheric water vapor concns. Conversion to coal HFCVs may improve health but would damage climate more than fossil/elec. hybrids. The real cost of hydrogen from wind electrolysis may be below that of U.S. gasoline.
- 44Jacobson, M. Z. Effects of Wind-powered Hydrogen Fuel Cell Vehicles on Stratospheric Ozone and Global Climate. Geophys. Res. Lett. 2008, 35 (19), L19803 DOI: 10.1029/2008GL03510244Effects of wind-powered hydrogen fuel cell vehicles on stratospheric ozone and global climateJacobson, Mark Z.Geophysical Research Letters (2008), 35 (19), L19803/1-L19803/5CODEN: GPRLAJ; ISSN:0094-8276. (American Geophysical Union)A review. Converting the world's fossil-fuel onroad vehicles (FFOV) to hydrogen fuel cell vehicles (HFCV), where the H2 is produced by wind-powered electrolysis, is estd. to reduce global fossil, biofuel, and biomass-burning emissions of CO2 by ∼13.4%, NOx ∼23.0%, nonmethane org. gases ∼18.9%, black carbon ∼8% H2 ∼3.2% (at 3% leakage), and H2O ∼0.2%. Over 10 years, such redns. were calcd. to reduce tropospheric CO ∼5%, NOx ∼5-13%, most org. gases ∼3-15%, OH ∼4%, ozone ∼6%, and PAN ∼13%, but to increase tropospheric CH4 ∼0.25% due to the lower OH. Lower OH also increased upper tropospheric/lower stratospheric ozone, increasing its global column by ∼0.41%. WHFCV cooled the troposphere and warmed the stratosphere, reduced aerosol and cloud surface areas, and increased pptn. Other renewable-powered HFCV or battery elec. vehicles should have similar impacts.
- 45van Ruijven, B.; Lamarque, J.-F.; van Vuuren, D. P.; Kram, T.; Eerens, H. Emission Scenarios for a Global Hydrogen Economy and the Consequences for Global Air Pollution. Global Environ. Change 2011, 21 (3), 983– 994, DOI: 10.1016/j.gloenvcha.2011.03.013There is no corresponding record for this reference.
- 46Bond, S. W.; Gül, T.; Reimann, S.; Buchmann, B.; Wokaun, A. Emissions of Anthropogenic Hydrogen to the Atmosphere during the Potential Transition to an Increasingly H2-Intensive Economy. Int. J. Hydrogen Energ 2011, 36 (1), 1122– 1135, DOI: 10.1016/j.ijhydene.2010.10.01646Emissions of anthropogenic hydrogen to the atmosphere during the potential transition to an increasingly H2-intensive economyBond, S. W.; Guel, T.; Reimann, S.; Buchmann, B.; Wokaun, A.International Journal of Hydrogen Energy (2011), 36 (1), 1122-1135CODEN: IJHEDX; ISSN:0360-3199. (Elsevier Ltd.)Current and future anthropogenic atm. H2 emissions from technol. processes were assessed. Current emissions are dominated by direct exhaust gas of road-based motor vehicles and losses during industrial H2 prodn. from fossil fuels. H2 emissions from transportation were estd. to be 4.5 Tg for 2010. An addnl. ∼0.5-2 Tg H2 were estd. to be lost to the atm. from industrial processes in 2010. In 2020, emissions from transportation are estd. to be ∼50% of those in 2010. Future emissions will occur as losses along the entire prodn., distribution, and end-use chain, including emissions from H2 fuel cell vehicles (FCV). In 2050, overall anthropogenic H2 emissions will only approach current levels at high-end loss rates; direct emissions from transportation are expected to be significantly lower than current levels. In 2100, an av. 0.5% loss rate would result in overall H2 emissions exceeding current levels, even with no net H2 emissions from FCV; however, based on an av. 0.1% loss rate, H2 emission factors from FCV on the order of 120-170 mg/km are projected to result in overall anthropogenic H2 emissions similar to 2010 levels.
- 47IEA. Global Methane Tracker Documentation 2022 Version. 2022. https://iea.blob.core.windows.net/assets/b5f6bb13-76ce-48ea-8fdb-3d4f8b58c838/GlobalMethaneTracker_documentation.pdf (last accessed 2024-01-12).There is no corresponding record for this reference.
- 48Gorski, J.; Jutt, T.; Wu, K. T. Carbon Intensity of Blue Hydrogen Production. 2021. https://www.pembina.org/reports/carbon-intensity-of-blue-hydrogen-revised.pdf (last accessed 2024-01-12).There is no corresponding record for this reference.
- 49IRENA. World Energy Transitions Outlook 2022. 2022. https://www.irena.org/Digital-Report/World-Energy-Transitions-Outlook-2022 (last accessed 2024-01-12).There is no corresponding record for this reference.
- 50Bertagni, M. B.; Socolow, R. H.; Martirez, J. M. P.; Carter, E. A.; Greig, C.; Ju, Y.; Lieuwen, T.; Mueller, M. E.; Sundaresan, S.; Wang, R.; Zondlo, M. A.; Porporato, A. Minimizing the Impacts of the Ammonia Economy on the Nitrogen Cycle and Climate. Proc. Natl. Acad. Sci. United States Am. 2023, 120 (46), e2311728120 DOI: 10.1073/pnas.2311728120There is no corresponding record for this reference.
- 51Wolfram, P.; Kyle, P.; Zhang, X.; Gkantonas, S.; Smith, S. Using Ammonia as a Shipping Fuel Could Disturb the Nitrogen Cycle. Nat. Energy 2022, 7 (12), 1112– 1114, DOI: 10.1038/s41560-022-01124-451Using ammonia as a shipping fuel could disturb the nitrogen cycleWolfram, Paul; Kyle, Page; Zhang, Xin; Gkantonas, Savvas; Smith, StevenNature Energy (2022), 7 (12), 1112-1114CODEN: NEANFD; ISSN:2058-7546. (Nature Portfolio)A polemic in response to Paul Wolfram et al is given. Ammonia has been proposed as a shipping fuel, yet potential adverse side-effects are poorly understood. We argue that if nitrogen releases from ammonia are not tightly controlled, the scale of the demands of maritime transport are such that the global nitrogen cycle could be substantially altered.
- 52Schaller, K. V.; Gruber, C. Hydrogen Powered Fuel-Cell Buses Meet Future Transport Challenges. 2001. https://www.citelec.org/eledrive/Afuelcellarticles/PP301.PDF (last accessed 2024-01-12).There is no corresponding record for this reference.
- 53Marcinkoski, J.; Vijayagopal, R.; Adams, J.; James, B.; Kopasz, J.; Ahluwalia, R. DOE Advanced Truck Technologies: Subsection of the Electrified Powertrain Roadmap Technical Targets for Hydrogen-Fueled Long-Haul Tractor-Trailer Trucks. 2019. https://www.hydrogen.energy.gov/docs/hydrogenprogramlibraries/pdfs/19006_hydrogen_class8_long_haul_truck_targets.pdf?Status=Master (last accessed 2024-01-12).There is no corresponding record for this reference.
- 54Ueckerdt, F.; Bauer, C.; Dirnaichner, A.; Everall, J.; Sacchi, R.; Luderer, G. Potential and Risks of Hydrogen-Based e-Fuels in Climate Change Mitigation. Nat. Clim Change 2021, 11 (5), 384– 393, DOI: 10.1038/s41558-021-01032-754Potential and risks of hydrogen-based e-fuels in climate change mitigationUeckerdt, Falko; Bauer, Christian; Dirnaichner, Alois; Everall, Jordan; Sacchi, Romain; Luderer, GunnarNature Climate Change (2021), 11 (5), 384-393CODEN: NCCACZ; ISSN:1758-6798. (Nature Portfolio)Abstr.: E-fuels promise to replace fossil fuels with renewable electricity without the demand-side transformations required for a direct electrification. However, e-fuels' versatility is counterbalanced by their fragile climate effectiveness, high costs and uncertain availability. E-fuel mitigation costs are euro800-1,200 per tCO2. Large-scale deployment could reduce costs to euro20-270 per tCO2 until 2050, yet it is unlikely that e-fuels will become cheap and abundant early enough. Neglecting demand-side transformations threatens to lock in a fossil-fuel dependency if e-fuels fall short of expectations. Sensible climate policy supports e-fuel deployment while hedging against the risk of their unavailability at large scale. Policies should be guided by a 'merit order of end uses' that prioritizes hydrogen and e-fuels for sectors that are inaccessible to direct electrification.
- 55Gudmundsson, O.; Thorsen, J. E. Source-to-Sink Efficiency of Blue and Green District Heating and Hydrogen-Based Heat Supply Systems. Smart Energy 2022, 6, 100071 DOI: 10.1016/j.segy.2022.10007155Source-to-sink efficiency of blue and green district heating and hydrogen-based heat supply systemsGudmundsson, Oddgeir; Thorsen, Jan EricSmart Energy (2022), 6 (), 100071CODEN: SEMNBM; ISSN:2666-9552. (Elsevier Ltd.)Hydrogen is commonly mentioned as a future proof energy carrier. Hydrogen supporters advocate for repurposing existing natural gas grids for a sustainable hydrogen supply. While the long-term vision of the hydrogen community is green hydrogen the community acknowledges that in the short term it will be to large extent manufd. from natural gas, but in a decarbonized way, giving it the name blue hydrogen. While hydrogen has a role to play in hard to decarbonize sectors its role for building heating demands is doubtful, as mature and more energy efficient alternatives exist. As building heat supply infrastructures built today will operate for the decades to come it is of highest importance to ensure that the most efficient and sustainable infrastructures are chosen. This paper compares the source to sink efficiencies of hydrogen-based heat supply system to a district heating system operating on the same primary energy source. The results show that a natural gas-based district heating could be 267% more efficient, and consequently have significantly lower global warming potential, than a blue hydrogen-based heat supply A renewable power-based district heating could achieve above 440% higher efficiency than green hydrogen-based heat supply system.
- 56de Kleijne, K.; de Coninck, H.; van Zelm, R.; Huijbregts, M. A. J.; Hanssen, S. V. The Many Greenhouse Gas Footprints of Green Hydrogen. Sustainable Energy Fuels 2022, 6, 4383– 4387, DOI: 10.1039/D2SE00444E56The many greenhouse gas footprints of green hydrogende Kleijne, Kiane; de Coninck, Heleen; van Zelm, Rosalie; Huijbregts, Mark A. J.; Hanssen, Steef V.Sustainable Energy & Fuels (2022), 6 (19), 4383-4387CODEN: SEFUA7; ISSN:2398-4902. (Royal Society of Chemistry)Green hydrogen could contribute to climate change mitigation, but its greenhouse gas footprint varies with electricity source and allocation choices. Using life-cycle assessment we conclude that if electricity comes from addnl. renewable capacity, green hydrogen outperforms fossil-based hydrogen. In the short run, alternative uses of renewable electricity likely achieve greater emission redns.
- 57CE Delft. Additionality of Renewable Electricity for Green Hydrogen Production in the EU. 2022. https://cedelft.eu/wp-content/uploads/sites/2/2022/12/CE_Delft_220358_Final_report.pdf (last accessed 2024-01-12).There is no corresponding record for this reference.
- 58Wolak, F. Re: Section 45V Credit for Production of Clean Hydrogen and Additionality. 2023. https://static1.squarespace.com/static/53ab1feee4b0bef0179a1563/t/6452ad18d54ae3543c305f15/1683139864709/FCHEA+Additionality+Sign+On+Letter+Final+2023-5-4.pdf (last accessed 2024-01-12).There is no corresponding record for this reference.
- 59Pototschnig, A. Renewable Hydrogen and the “Additionality” Requirement: Why Making It More Complex than Is Needed?. European University Institute 2021, 1– 6, DOI: 10.2870/201657There is no corresponding record for this reference.
- 60Ocko, I. B.; Hamburg, S. P.; Jacob, D. J.; Keith, D. W.; Keohane, N. O.; Oppenheimer, M.; Roy-Mayhew, J. D.; Schrag, D. P.; Pacala, S. W. Unmask Temporal Trade-Offs in Climate Policy Debates. Science 2017, 356 (6337), 492– 493, DOI: 10.1126/science.aaj235060Unmask temporal trade-offs in climate policy debatesOcko, Ilissa B.; Hamburg, Steven P.; Jacob, Daniel J.; Keith, David W.; Keohabne, Nathaniel O.; Oppenheimer, Michael; Roy-Mayhew, Joseph D.; Schrag, Daniel P.; Pacala, Stephen W.Science (Washington, DC, United States) (2017), 356 (6337), 492-493CODEN: SCIEAS; ISSN:0036-8075. (American Association for the Advancement of Science)There is no expanded citation for this reference.
- 61Deng, H.; Bielicki, J. M.; Oppenheimer, M.; Fitts, J. P.; Peters, C. A. Leakage Risks of Geologic CO2 Storage and the Impacts on the Global Energy System and Climate Change Mitigation. Clim. Chang. 2017, 144 (2), 151– 163, DOI: 10.1007/s10584-017-2035-861Leakage risks of geologic CO2 storage and the impacts on the global energy system and climate change mitigationDeng, Hang; Bielicki, Jeffrey M.; Oppenheimer, Michael; Fitts, Jeffrey P.; Peters, Catherine A.Climatic Change (2017), 144 (2), 151-163CODEN: CLCHDX; ISSN:0165-0009. (Springer)This study investigated how subsurface and atm. leakage from geol. CO2 storage reservoirs could impact the deployment of Carbon Capture and Storage (CCS) in the global energy system. The Leakage Risk Monetization Model was used to est. the costs of leakage for representative CO2 injection scenarios, and these costs were incorporated into the Global Change Assessment Model. Worst-case scenarios of CO2 leakage risk, which assume that all leakage pathway permeabilities are extremely high, were simulated. Even with this extreme assumption, the assocd. costs of monitoring, treatment, containment, and remediation resulted in minor shifts in the global energy system. For example, the redn. in CCS deployment in the electricity sector was 3% for the "high" leakage scenario, with replacement coming from fossil fuel and biomass without CCS, nuclear power, and renewable energy. In other words, the impact on CCS deployment under a realistic leakage scenario is likely to be negligible. We also quantified how the resulting shifts will impact atm. CO2 concns. Under a carbon tax that achieves an atm. CO2 concn. of 480 ppm in 2100, technol. shifts due to leakage costs would increase this concn. by less than 5 ppm. It is important to emphasize that this increase does not result from leaked CO2 that reaches the land surface, which is minimal due to secondary trapping in geol. strata above the storage reservoir. The overall conclusion is that leakage risks and assocd. costs will likely not interfere with the effectiveness of policies for climate change mitigation.
- 62Vinca, A.; Emmerling, J.; Tavoni, M. Bearing the Cost of Stored Carbon Leakage. Front. Energy Res. 2018, 6, 40, DOI: 10.3389/fenrg.2018.00040There is no corresponding record for this reference.
- 63Hidden hydrogen: Earth may hold vast stores of a renewable, carbon-free fuel. Science https://www.science.org/content/article/hidden-hydrogen-earth-may-hold-vast-stores-renewable-carbon-free-fuel (last accessed 2024-01-12).There is no corresponding record for this reference.
Supporting Information
Supporting Information
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.3c09030.
More detailed information about methods and data used in this study as well as additional figures that show the climate impact of hydrogen pathways relative to other alternatives under the 2030 condition (PDF)
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