The transition towards cleaner energy is an immediate priority. Achieving net-zero emissions by 2050 requires continuous efforts and investments from both government and industries over the next decade. Hydrogen could play a critical role in achieving carbon emission reduction goals (Figure 1). In December 2020, the Government of Canada announced its hydrogen strategy to assert Canadian leadership in hydrogen technologies and accelerate hydrogen adoption across multiple sectors of the economy.1 One challenge in implementing a national hydrogen strategy is ensuring safe and cost-effective transportation from points of production to points of use. Pipelines are the most convenient, safe and environmentally friendly way to transport natural resources. Canada already has an extensive pipeline infrastructure – approximately 840,000 km – which is primarily used for natural gas (NG) transportation.2 Leveraging this existing infrastructure can enable the transportation of large volumes of hydrogen to end-use locations. However, the lack of knowledge related to the safety and reliability of hydrogen-specific distribution networks has led to social acceptance issues, delaying implementation. Blending hydrogen into the existing NG pipelines is an attractive approach to help decarbonize heavy industry. For instance, a 20 vol% hydrogen blend can lead to an approximately 7% decrease in carbon emissions from a combustion perspective.3 This approach allows for a gradual transition while utilizing the existing pipeline infrastructure and minimizing the need for extensive modifications.
Repurposing the NG pipeline infrastructure for hydrogen blend indeed poses complex challenges that need to be addressed through extensive research. Key technical gaps such as material compatibility, fire safety, risk assessment and reliability must be investigated thoroughly. For example, one specific challenge is the occurrence of hydrogen-assisted environmental cracking (HAEC), a potential failure mode that is not yet fully understood in the context of hydrogen blending in NG pipelines. HAEC can occur under both dynamic and static stress on pipeline steel. Hydrogen, being the smallest molecule, can diffuse into the steel leading to reduced ductility, fracture toughness and accelerated fatigue crack growth, which may ultimately result in pipeline failure. Although leaks and ruptures are rare, their occurrence can have severe environmental impacts. Also, it is crucial to understand and mitigate the safety implications of fire hazards related to hydrogen blend gas leaks. Unlike NG, hydrogen exhibits distinct detonation characteristics including a broader explosion range, lower minimum ignition energy, higher flame velocity, flame temperature and greater diffusivity.4 Blending hydrogen with NG at low concentrations (e.g. 5%) can be done safely without significantly increasing risks in end-use applications. However, the safe hydrogen blend concentration may vary depending on NG compositions and pipeline infrastructure. Introducing hydrogen into the existing NG pipelines requires extensive testing and modifications to pipeline monitoring and maintenance practices ensuring safe and reliable operation. Addressing these technical challenges is crucial for the successful implementation of hydrogen blending in the existing NG pipeline infrastructure. Besides the production and transportation of hydrogen blends, there is also a need for extensive research to address their safety and compatibility related to storage and end-use applications. This article aims to provide a summary of recent research advances, standardization efforts and fire safety challenges related to hydrogen blends. The goal is to enhance awareness, promote knowledge mobilization and foster cooperation among various stakeholders involved in the hydrogen industry.
Recent research advances
Recently, extensive research was carried out to investigate the mechanical properties of pipeline steels under hydrogen influence. Researchers have used various materials including specific grades of vintage steel in diverse conditions. These conditions include exposure to gases like air, hydrogen, helium, nitrogen, NG and gas mixtures (air and hydrogen; NG and hydrogen). These studies suggested that while the strength of the materials is not greatly affected, their ability to resist crack propagation is significantly impacted in the presence of hydrogen. The combustion characteristics of pure hydrogen are generally understood. However, the influence of hydrogen in the hydrogen blend with NG and the risks associated with NG pipeline infrastructure remain largely unknown. Only a few recent studies have employed numerical simulation techniques to model cases of leaks from hydrogen blends. Recent studies have explored various aspects of hydrogen blend safety using different computational methods.5,6 These safety studies include fire damage investigation, thermal radiation introduction and lethal distance calculation. However, many of these models are problem-specific, and they lack experimental validation and comprehensive analysis of different fire scenarios. Hence, there is a need to develop a comprehensive fire and hazard analysis tool tailored specifically for transporting hydrogen in NG networks.
The United Kingdom, Germany and several other European countries have recently started producing and distributing a 20 vol% hydrogen blend through their existing NG pipelines.7 In 2021, Enbridge, which is the largest Canadian NG storage, transmission and distribution company, launched a pilot project to produce and distribute a 2 vol% hydrogen blend to approximately 3,600 consumers in Markham, Ontario. This pilot project is expected to reduce up to 117 tons of carbon dioxide from the atmosphere every year.8 Similarly, ATCO Gas, an Alberta-based gas distribution company, also initiated a pilot project in 2022 to produce and distribute a 5 vol% hydrogen blend to around 2,100 consumers in Fort Saskatchewan, Alberta.9 The European Gas Research Group is actively involved in multiple projects focused on hydrogen blends. These projects aim to address safety and compatibility concerns, with the ultimate goal of accelerating the adoption of hydrogen and facilitating its large-scale implementation.10 The US Department of Energy also has several initiatives focused on addressing the technical challenges related to blending hydrogen into NG pipelines. These initiatives aim to facilitate the safe and efficient integration of hydrogen into existing NG infrastructure.11 The International Association for Hydrogen Safety, which is a non-profit institution, is promoting hydrogen safety research, education and training.12
Standardization efforts
Production/infrastructure
As mentioned earlier, injecting hydrogen into the NG pipelines is the easiest way to produce hydrogen blends (Figure 2). Hence, it is crucial to develop specific codes, standards and regulations regarding hydrogen blends. The ISO 13686:2013 ‘Natural gas – Quality designation’, which was reviewed and confirmed in 2020, specifies the parameters necessary to describe finally processed blended natural gas, with a particular emphasis on health and safety considerations.13 The German Technical and Scientific Association for Gas and Water (DVGW) has established a comprehensive set of standards and a robust regulatory framework for the operation, development and safety of hydrogen-rich gases.14 One notable standard is the DVGW G 265-3:2022, which specifically focuses on the production, construction and operation of systems for hydrogen blends.15 Additionally, the DVGW G 260:2021 standard addresses the properties of fuel gases in the public gas supply, including hydrogen blends.16
Storage
The CSA Z341S1:23 supplement, developed by CSA, focuses on the underground storage of hydrogen and hydrogen blends.17 This supplement sets out minimum requirements for the design, construction, operation, maintenance, abandonment and safety of storing hydrogen and hydrogen blends in underground formations. It also covers the associated equipment involved in the storage process. By outlining these requirements, the CSA Z341S1:23 supplement plays a crucial role in ensuring the safe and efficient storage of hydrogen and hydrogen blends in underground facilities.
Transportation/transmission
In 2023, the Canadian Standard Association updated the CSA Z662 standard ‘Oil and Gas Pipeline System’ to include hydrogen and hydrogen blends for Canadian pipeline infrastructure.18 These recent updates necessitate engineering assessments on material selection and pipeline design to effectively address the potential adverse effects of hydrogen on pipelines. The CGA G-5.6: 2005 standard, jointly developed by the European Industrial Gases Association and Compressed Gas Association, is an important guideline for metallic transmission and distribution systems that convey pure hydrogen and hydrogen blends. The standard was reaffirmed in 2013, emphasizing its continued relevance and importance.19 The ASME B31.12:2023 standard, titled ‘Hydrogen Piping and Pipelines’, provides guidelines for systems that handle gaseous hydrogen and hydrogen blends, including provisions for liquid hydrogen service.20 The DVGW G 407:2022 standard provides guidelines for the conversion of gas pipelines to steel pipelines with up to 16 bar operating pressure to accommodate pure hydrogen or hydrogen blends.21 The DVGW G 463 standard, updated in 2021, applies to the planning and construction of high-pressure steel pipelines with an operating pressure exceeding 16 bar supporting the transport of hydrogen.22 The DVGW G 221:2021 standard applies to gas infrastructure for supplying hydrogen and hydrogen blends. This standard is designed to facilitate the continued operation of existing gas infrastructure while also providing transitional solutions for the construction and conversion of gas networks to accommodate hydrogen.23 The Institution of Gas Engineers and Managers (IGEM) has developed supplements to support the transmission of hydrogen blends. These supplements include (i) IGEM/TD/1 Edition 6 Supplement 2 – High Pressure Hydrogen Pipelines,24 (ii) IGEM/TD/3 Edition 5 Supplement 1 – Repurposing of Natural Gas (NG) pipelines with MOP not exceeding 7 bar for NG/Hydrogen blends,25 and (iii) IGEM/TD/13 Edition 3 Supplement 2 – Pressure regulating installations for Natural Gas/Hydrogen blended mixtures at pressures not exceeding 7 bar.26 The AS/NZS 4645 standard series, jointly developed by Australia and New Zealand, focuses on the design, construction, operation and maintenance of gas distribution systems specifically for hydrogen blends up to 15 vol%.
End-use
In Canada, regulations related to hydrogen blending into the NG pipelines and hydrogen tolerances in end-use appliances may vary by province or territory. For example, Ontario regulations 210/01 ‘Oil and Gas Pipeline Systems’ and 212/01 ‘Gaseous Fuels’ can be applied to hydrogen blends for gas pipelines and end-use appliances. The CSA Z662 standard also covers the transmission of hydrogen blends and their tolerances in end-use appliances.27 The CSA/ANSI Z21.1:24 CSA 1.1:24 applies to new domestic cooking gas appliances designed for pure and mixed gases. While originally intended for other gases, this standard can potentially be extended to cover appliances designed for hydrogen blends as well. In Europe, contemporary domestic appliances are certified according to the Gas Appliance Regulation guidelines. As part of the certification process, these appliances are tested using a specific test gas blend that contains 23 vol% hydrogen.27
Fire safety
Hydrogen is a highly reactive and potentially explosive gas, posing similar risks to other flammable fuels.28,29 It is also lighter than air, which indicates that it can disperse rapidly into the atmosphere. Additionally, hydrogen is odourless, colourless and tasteless, making it difficult for humans to detect leaks using their senses alone. Hence, the National Fire Protection Association (NFPA) assigned hydrogen the highest flammability rating of 4. This rating signifies that hydrogen is indeed highly flammable, even when mixed with ordinary air in small amounts. There are several safety codes and standards that apply to hydrogen blending in the NG infrastructure.30 These codes encompass regulations for both NG and hydrogen individually, as well as regulations for hydrogen blends. However, it is important to note that certain gaps must be addressed when contemplating the introduction of hydrogen blends into the existing gas infrastructure. For example, the ASME B31.12:2023 standard is specifically designed to address hydrogen blends that contain more than 10 vol% hydrogen and operating pressures below 3,000 psi.20 However, NFPA 2:2023 ‘Hydrogen Technologies Code’ applies to hydrogen blends with hydrogen concentrations above 95% by volume, without any specific pressure limits.30
Conclusions
Hydrogen blends have the potential to contribute significantly to the reduction of carbon emissions from the use of NG. However, it is crucial to conduct extensive research to demonstrate their safe implementation and adaptation. This research should focus on developing new standards and updating existing ones to accommodate hydrogen blends. Additionally, considerable effort is required to establish maximum hydrogen tolerances for end-use appliances.
For more information, email
Rokib.Hassan@nrc-cnrc.gc.ca or MdAminul.Islam@nrc-cnrc.gc.ca
References
- Natural Resources Canada ‘Hydrogen Strategy for Canada: Seizing the opportunities for hydrogen’ 2020.
- Natural Resources Canada ‘Pipelines Across Canada’ 2020.
- E.A. Polman, J.C. De Laat, M. Crowther ‘Reduction of CO2 emissions by adding hydrogen to natural gas’ IEA Green House Gas R&D program, 2003.
- Y. Li, Z. Kuang, Z. Fan, J. Shuai ‘Evaluation of the safe separation distances of hydrogen-blended natural gas pipelines in a jet fire scenario’ Int. J. Hydrog. Energy 48(49), 18804–18815, 2023.
- C.J. Wang, J.X. Wen, Z.B. Chen, S. Dembele ‘Predicting radiative characteristics of hydrogen and hydrogen/methane jet fires using FireFOAM’ Int. J. Hydrog. Energy 39(35), 20560–20569, 2014.
- C. Zhou, Z. Yang, G. Chen, Q. Zhang, Y. Yang ‘Study on leakage and explosion consequence for hydrogen blended natural gas in urban distribution networks’ Int. J. Hydrog. Energy 47(63), 27096–27115, 2022.
- Hydrogeninsight ‘German gas operator says 20% hydrogen blending trial in 100 homes has been ‘100% trouble-free’ after six months’ 2023.
- Enbridge ‘Enbridge and clean hydrogen’.
- ATCO ‘Fort Saskatchewan hydrogen blending project’.
- The European Gas Research Group ‘Hydrogen’.
- The US Department of Energy ‘HyBlend: Opportunities for hydrogen blending in natural gas pipelines’ 2022.
- The International Association for Hydrogen Safety ‘HySafe’.
- ISO 13686:2013 ‘Natural gas – Quality designation’ 2020.
- M.A. Kappes, T. Perez ‘Hydrogen blending in existing natural gas transmission pipelines: a review of hydrogen embrittlement, governing codes and life prediction methods’ Corros. Rev. 41(3), 319–347, 2023.
- DVGW G 265-3:2022 ‘Systems for feeding hydrogen into gas and hydrogen networks; Planning, manufacturing, construction, testing, commissioning and operation’ 2022.
- DVGW G 260:2021 ‘Gas Quality’ 2021.
- The CSA Group ‘Hydrogen storage and transport beyond pipelines: regulations and standardization’ 2023.
- The CSA Group ‘Assessment of natural gas pipeline materials for hydrogen service’ 2024.
- CGA G-5.6 ‘Hydrogen pipeline systems’ 2013 (reaffirmed).
- ASME B31.12:2023, ‘Hydrogen Piping and Pipelines’ 2024.
- DVGW G 407:2022 ‘Conversion of gas pipelines from steel pipes up to 16 bar operating pressure for the distribution of hydrogen-containing methane-rich gases and hydrogen’ 2022.
- DVGW G 463:2021 ‘High-pressure gas pipes made of steel pipes for a design pressure of more than 16 bar; Planning and construction’ 2021.
- DVGW G 221:2021 ‘Guidelines for the application of the DVGW regulations to the grid-bound supply of hydrogen-containing gases and hydrogen to the general public’ 2021.
- IGEM/TD/ 1 Edition 6 Supplement 2 ‘High-pressure Hydrogen Pipelines’ 2021.
- IGEM/TD/3 Edition 5 Supplement 1 ‘Repurposing of Natural Gas (NG) pipelines with MOP not exceeding 7 bar for NG/Hydrogen blends’ 2022.
- IGEM/TD/13 Edition 3 Supplement 2 ‘Pressure regulating installations for Natural Gas/Hydrogen blended mixtures at pressures not exceeding 7 bar’ 2024.
- Y. Yoo, H. Baran, N. Glass, R. Baker ‘H₂ blending into the Canadian NG grid network and H₂ tolerances in end-use appliances’ 2022.
- DET-TRONICS ‘Hydrogen and fire safety’ 2020.
- Department of Energy ‘Hydrogen safety’ USA.
- A.M. Glover, J.T. Mohr, A.R. Baird ‘Codes and Standards Assessment for Hydrogen Blends into the Natural Gas Infrastructure’ SAND2021-12478, Sandia National Laboratories, 2021.
About the Author
Rokib Hassan
M. Rokib Hassan, PhD, Associate Research Officer, Fire Safety, Construction Research Centre, National Research Council Canada. Rokib.Hassan@nrc-cnrc.gc.ca
Dr Aminul Islam
Dr Aminul Islam is a materials engineer specializing in tribology, materials characterization, wear, corrosion, and failure analysis. Over the past few years, Dr Islam has applied his expertise to assess the suitability of various materials for hydrogen and developed new procedures for testing material compatibility with hydrogen. MdAminul.Islam@nrc-cnrc.gc.ca
Jasveer Singh
Jasveer Singh, COOP Student, Fire Safety, Construction Research Centre, National Research Council Canada
