Unpacking the Myths: Frequently Asked Questions on Hydrogen Blending
As the world shifts towards cleaner energy sources in order to meet sustainability goals, the use of hydrogen as a fuel is gaining significant attention. However, the integration of hydrogen gas into existing natural gas infrastructure raises several questions and concerns. In this blog post, we will address some of the top concerns for hydrogen blending, along with ongoing research and development efforts that are paving the way for safe and efficient use of hydrogen gas blends into our gas infrastructures and utility networks.
Will odorization be affected by hydrogen blended gases?
No. Typically, odorants are added to gases or gas blends as a safety feature. Because hydrogen is an odorless gas, the blending of hydrogen into natural gases may dilute the smell, but it will not impact the effectiveness of the odorant (Hydrogen Blending into Natural Gas Pipeline Infrastructure: Review of the State of Technology, 2022).
A study published by Hy4Heat identified a number of suitable odorants for up to 100% hydrogen gas grids. The study breaks down five different odorants commonly used in natural gas grids and tests the mixtures effects on pipelines (metal and plastic), appliances (hydrogen boiler), and PEM (proton-exchange membrane) fuel cells. The odorants were evaluated by six panelists using the olfactory test method. Results from the evaluation showed that all odorants were deemed suitable in a 100% hydrogen gas grid for combustion appliances, passing the test criteria for both odor concentration and intensity (Hydrogen Odorant and Leak Detection Part 1, 2020).
The tables below display information about the five odorants used in the Hy4Heat study. The first table explains the respective odorant compound makeups and the rationale for using the specific odorant, and the second table displays the test results for the various leak detection, degradation, and economic tests for the five odorants.
(green = provides characteristic gas leak smell, no degradation/damage to infrastructure, cost-effective; yellow = some characteristic gas leak smell, some degradation/damage to infrastructure, may/may not be cost effective; red = no strong characteristic gas leak smell, degradation/damage to infrastructure, cost intensive to implement.)
How does hydrogen blending affect gas leaks?
Most natural gas distribution mains and service lines are made from polyethylene (plastic), and transport gas at low pressures. Hydrogen molecules are incredibly small, therefore they pose a potential risk for leakage at certain concentrations. Studies have suggested that gas blends containing 5-20% concentration of hydrogen are not at risk for preferential leaks (Numerical study of leakage characteristics of hydrogen-blended natural gas in buried pipelines, 2024).
Leak detection capabilities like acoustic monitors or sniff tests offer techniques to spot leaks before they pose too large of a risk. And though hydrogen blended gas has the potential to exacerbate pipeline cracks, utilities and gas networks that maintain proactive care in sustaining their pipeline integrity should not be at risk for an increase in gas leaks when blending up to 20% of hydrogen concentration (Assessing the Viability of Hydrogen Proposals, 2022).
Does hydrogen cause embrittlement in steel pipelines?
Hydrogen embrittlement is a type of corrosion or deterioration that stems from the ingress (or entering) of hydrogen into a material. The ingress of hydrogen into various components can lead to reduced ductility, compromised load-bearing capacity, cracking, and even failures at stress levels below the specified yield-stress of materials (Polymeric Materials in Corrosion Inhibition, 2022).
It is possible for hydrogen embrittlement to occur through applied tensile stress or dissolving of hydrogen molecules into the material. Though studies show that hydrogen injection can potentially result in weldment cracks, hardened steel, or other deterioration, hydrogen embrittlement does not affect all metallic materials equally. The most vulnerable materials for embrittlement are certain steels, titanium alloys, and aluminum alloys (Hydrogen embrittlement in hydrogen-blended natural gas transportation systems: A review, 2023). On the other hand, hydrogen has no impact on polyethylene (plastic) materials, making this the ideal material for hydrogen and hydrogen blended gas piping.
Studies report that embrittlement impacts are seen at high pressures of gas (higher pressures are utilized during the transportation process of gas). At lower pressures (during the distribution process) there are far fewer embrittlement impacts. In certain cases, steel pipelines have transported 100% hydrogen gas for multiple years and faced no issues related to embrittlement. Embrittlement impacts remain contingent on various factors of the piping and material (including age, thickness, integrity, etc.) (Hydrogen Embrittlement, 2022).
How does hydrogen blending affect heating factors and values for gas?
Most gas companies maintain their own regulations to measure and uphold gas qualities. Heating value and the Wobbe index are two of the most common measures for gas quality.
Let’s break it down: Heating value is understood as the amount of heat released during the combustion of a specified fuel. The Wobbe index is a value used to define the gross heating value of a gas, divided by the square root of the gas’ specific gravity. The Wobbe index is a known indicator of the interchangeability of various fuel gases. The following chart shows the trends of Heating Value and Wobbe index for increasing concentrations of hydrogen blended with natural gas (Influence of hydrogen addition to pipeline natural gas on the combustion performance of a cooktop burner, 2019).
Hydrogen blended gas’ heating factors and values follow a downward slope, meaning as we increase the concentration (%) of hydrogen in the natural gas blend, there is a decrease in the heating value. As for the Wobbe index, as hydrogen concentration increases, there is a decrease in the Wobbe index value up until an 85-90% concentration of hydrogen. The Wobbe index values for methane and hydrogen gases are quite comparable, with the value for 100% methane gas being 1,215 Btu/scf and the value for 100% hydrogen gas being 1,039 Btu/scf (Influence of hydrogen addition to pipeline natural gas on the combustion performance of a cooktop burner, 2019).
How much do hydrogen blended gases reduce carbon emissions?
A study from 2020 compared the carbon emissions reductions of green and blue hydrogen at various volumetric concentrations of hydrogen blends with natural gas. The study compares the emissions factor of the hydrogen-natural gas blends (with both green and blue hydrogen blends) to the emissions factor of pure natural gas. In the table below, we observe a relatively similar reduction in carbon emissions rates with both green and blue hydrogen. For a complete substitution of natural gas with hydrogen gas, there is 100% reduction in emissions for green hydrogen, and about 84% reduction in emissions for blue hydrogen (The Role of Green and Blue Hydrogen in the Energy Transition: A technological and geopolitical perspective, 2021).
To put things into a different perspective, when burning 1 kilogram of methane natural gas, about 2.75 kilograms of carbon dioxide are released. When burning 1 kilogram of green hydrogen, no carbon dioxide is produced, only water (Climate Portal MIT, 2024). The process of creating the hydrogen is where carbon emissions can be a concern, however blue and green hydrogen offer methods of hydrogen creation that negate the carbon emissions and environmental impacts of the process.
Will hydrogen impact residential gas appliances?
A study done by the CSA (Compliance, Safety, and Accountability program) shows that most appliances are not impacted by hydrogen gas blends with up to 15% hydrogen concentration. The study highlighted that there were no major operational issues in appliances using hydrogen blends, and that they saw consistently decreased carbon emissions with increased hydrogen concentrations in gas blends (Appliance and Equipment Performance with Hydrogen-Enriched Natural Gases, 2021).
To read more about hydrogen’s impact on appliances, check out the two-part blog post: Hydrogen’s Impact on End-Use Appliances – Part 1
What is the cost of producing hydrogen for energy?
Though hydrogen is a largely abundant element, it is not a pure source of energy, but rather an energy carrier that must be produced from other sources. There are many ways to produce hydrogen from alternative sources, i.e. electrolysis to create green hydrogen, steam methane reforming (SMR) with carbon capture and storage (CCS) to create blue hydrogen, and SMR without CCS to create grey hydrogen.
The high cost of electrolysis to create hydrogen for energy was an initial barrier to adoption, however studies show that through technological advancements and learning curves, the cost will drive down over time (The Role of Green and Blue Hydrogen in the Energy Transition: A technological and geopolitical perspective, 2021). The table below displays the projected cost for producing green hydrogen, and blue hydrogen from both coal and gas resources.
Conclusion
While the integration of hydrogen into natural gas infrastructure presents some challenges, such as the potential for leaks at higher concentrations, it is encouraging for our energy sector to know that odorization can be effectively maintained, ensuring safety measures remain in place. Moreover, the ongoing research and development efforts regarding pipeline integrity and potential embrittlement are paving the way for the safe and efficient use of hydrogen blends in existing gas grids. By addressing these concerns, we can continue to explore the potential of hydrogen as a clean and sustainable energy source while mitigating potential risks.
Sources:
*sources are in order of appearance throughout the blogpost
- Hydrogen Blending into Natural Gas Pipeline Infrastructure: Review of the State of Technology, 2022. https://www.nrel.gov/docs/fy23osti/81704.pdf
- Hydrogen Odorant and Leak Detection Part 1, 2020. Hydrogen+Odorant+Final+Report+amended+Nov+2020.pdf (squarespace.com)
- Numerical study of leakage characteristics of hydrogen-blended natural gas in buried pipelines, 2024. Numerical study of leakage characteristics of hydrogen-blended natural gas in buried pipelines - ScienceDirect
- Assessing the Viability of Hydrogen Proposals, 2022. Assessing-the-Viability-of-Hydrogen-Proposals.pdf (energyinnovation.org)
- Hydrogen embrittlement in hydrogen-blended natural gas transportation systems: A review, 2023. Hydrogen embrittlement in hydrogen-blended natural gas transportation systems: A review - ScienceDirect
- Hydrogen Embrittlement, 2022. Hydrogen Embrittlement - an overview | ScienceDirect Topics
- Influence of hydrogen addition to pipeline natural gas on the combustion performance of a cooktop burner, 2019. Heating value and Wobbe Index variation of hydrogen/natural gas... | Download Scientific Diagram (researchgate.net)
- The Role of Green and Blue Hydrogen in the Energy Transition: A technological and geopolitical perspective, 2021. Sustainability | Free Full-Text | The Role of Green and Blue Hydrogen in the Energy Transition—A Technological and Geopolitical Perspective (mdpi.com)
- Climate Portal MIT, 2024. Hydrogen | MIT Climate Portal
- Appliance and Equipment Performance with Hydrogen-Enriched Natural Gases, 2021. Appliance and Equipment Performance with Hydrogen-Enriched Natural Gases - CSA Group