BDM Hydrogen and CCUS APAC and EMEA, Energy Transition
Hydrogen, which does not create any carbon emissions when burned, is a pivotal resource in the energy transition. This abundantly available, natural element has the potential to accelerate decarbonization, making it an essential part of a carbon-neutral society.
As hydrogen continues to garner new levels of interest, so do the impacts of hydrogen production. But as the new energy economy matures, the hydrogen color spectrum — which assigns colors to various production techniques with different levels of carbon emissions — is no longer the preferred approach to evaluating hydrogen's environmental footprint. The color spectrum ranges from green hydrogen, which is produced with renewable energy only and has the lowest carbon emissions, to black hydrogen, which is produced with the most.
Not all hydrogen is created equally, and the color spectrum can be a useful tool for understanding these various production methods at a high level. However, considering production methodologies in isolation from other factors is a misleading indicator. Simply put, a quantitative measure of the emissions associated with hydrogen will be essential as the hydrogen economy matures. An approach based on carbon intensity can provide a transparent, universal measure of hydrogen's environmental impact across the value chain.
Blue Hydrogen vs. Green Hydrogen: Understanding the Hydrogen Color Spectrum
The color spectrum categorizes various approaches for producing hydrogen. Each color describes a production method. While blue hydrogen vs. green hydrogen is the most talked about, many other process colors exist.
Green Hydrogen
Electrolysis splits water into oxygen and hydrogen, utilizing renewable electricity. The energy must come from renewable sources such as wind or solar as this classification is intended to be emissions-free. John Crane is proud to support one of the world's largest green hydrogen projects with our dry gas seals, high-performance couplings and gas filters. Planned for operations in 2026, the plant is set to produce 600 tonnes per day of zero-carbon hydrogen.
Blue Hydrogen
Natural gas feedstock undergoes reforming, such as steam methane reforming (SMR) or autothermal reforming (ATR), and partial oxidation, converting methane into hydrogen and CO2. The process pairs with carbon capture utilization and storage (CCUS) to prevent the release of emissions. John Crane provides the sealing technology for one of Canada's largest blue hydrogen production sites, located in Edmonton, Canada.
Grey Hydrogen
Natural gas is separated into hydrogen and carbon dioxide by reforming. Unlike blue hydrogen, CO2 emissions are discharged into the atmosphere.
Pink Hydrogen
Nuclear-powered electrolysis produces hydrogen from water; the energy spent is non-renewable, but the process is low-carbon.
Turquoise Hydrogen
A process called methane pyrolysis thermally decomposes methane into hydrogen and solid carbon, significantly reducing the release of CO2 gas.
Black and Brown Hydrogen
Gasification of hard coal (black) or soft lignite (brown) produces hydrogen. These production methods are considered some of the least environmentally conscious.
Yellow Hydrogen
Electrolysis powered by a mix of solar energy and other non-renewable sources produces hydrogen. This mix could create a significant carbon footprint depending on the amount and type of non-renewable energy sources used.
White or Gold Hydrogen
Hydrogen production occurs underground through natural processes and chemical reactions. When conducted in abandoned gas or oil wells, microbes break down organic matter in the absence of oxygen, yielding “gold” hydrogen gas as a byproduct. Gold hydrogen can also be extracted via drilling similar to natural gas production, which offers a potentially attractive pathway if large and accessible underground hydrogen resources can be found.
While these colors offer a simple way to distinguish between blue hydrogen vs. green hydrogen and more, the descriptors only tell part of the story. Investors, industry leaders and the public deserve to understand the complete picture when it comes to the hydrogen's carbon impact.
Looking Beyond the Hydrogen Color Spectrum
The limitations of the hydrogen color spectrum lie in its simplicity and the absence of any formal definition. It groups production methods but does not account for variations in carbon emissions within a color category.
There is no simple answer to the question, “What is green hydrogen?” Even terms such as “low-carbon” or “clean” hydrogen are inconsistent across projects, countries and regulatory bodies. A pragmatic characterization of environmental impact is essential to hydrogen's role in decreasing emissions. Carbon intensity (CI), a technology-agnostic measure of carbon footprint, offers a framework for describing hydrogen with universal commonality.
- Carbon Intensity (CI): The quantity of carbon in CO2 equivalent emitted per unit of hydrogen produced; the higher the CI score, the more adverse the environmental footprint.
A quantitative measure like CI is more telling than the process color alone. The transparency CI adds could help accelerate hydrogen projects by bolstering confidence with investors, creating consistency for astute market decisions and enabling interoperability between regulatory bodies worldwide.
However, establishing CI is complex and a clear approach to determining CI is critical to its success.
Factors Contributing to Carbon Intensity
Carbon emissions along the hydrogen value chain fall into various categories: feedstock, production, transportation, storage and final use. For an accurate representation of hydrogen's potential in global decarbonization, CI must consider emissions at every step of the value chain.
For example, a study by Wood Mackenzie found that water electrolysis (typically associated with “green hydrogen” production) could result in higher CO2 emissions than brown hydrogen if the electricity for the process came from grid power generated with unabated fossil fuels.
Accounting for all the emissions released throughout the hydrogen lifecycle is particularly challenging in terms of production and transportation.
Hydrogen Production
The carbon intensity of hydrogen varies greatly across production methods, so one color is not always less carbon-intensive than another.
Here's one example: Although using natural gas for SMR feedstock generates higher emissions than water electrolysis, the final CI depends on several factors, including the energy source powering the production as well as the carbon capture rate.
Consider a situation that uses renewable power to produce hydrogen through electrolysis (green hydrogen). Due to the intermittent nature of solar and wind, it may be necessary to leverage grid energy to support electrolysis at scale. However, grid energy impacts CI, as it may be fossil fuel-based, and emissions may be abated or unabated at the power plant level. However, incorporating energy storage into renewable hydrogen production, rather than grid power, can enable 100% renewable hydrogen production.
As another example, the range of CI associated with blue hydrogen varies broadly depending on where carbon capture is used in the process. There are two opportunities to decarbonize the production of blue hydrogen by SMR: at the point where feedstock gas (methane) is burned to enable SMR, and after the SMR process has produced CO2. According to the IEA, capturing both sources of CO2 can result in a 93% capture rate, as contrasted with a much lower 60% for partial capture.
Hydrogen Transportation
A complete evaluation of CI considers whether and in which form hydrogen is delivered by pipeline, truck, rail or ship. The fuels that power these transportation modes emit carbon, driving higher CI scores. There are a few challenges.
Preparing hydrogen for transportation may involve liquefaction, which requires energy to maintain cryogenic temperatures. Pipeline transportation is possible at ambient temperature, but power is still needed to compress hydrogen gas, which impacts CI.
Converting hydrogen to ammonia for transportation is an appealing alternative. This infrastructure and expertise is already well-established. However, the Haber-Bosch process for creating ammonia consumes significant energy, and a large amount of energy is needed to crack the ammonia back into hydrogen at the point of use.
There are, however, advantages in terms of carbon footprint when utilizing the ammonia molecule instead of cracking it back into hydrogen and nitrogen. For example, advancements within the maritime sector suggest that using transported ammonia as fuel could lower carbon emissions and CI compared to using common marine fuels. Another idea is to use the boil-off gas from liquid hydrogen as a fuel or part of the fuel in a liquid hydrogen carrier ship. To date, these technologies have not yet been widely adopted. Marine transport remains a significant contributor to CI, particularly for long-distance trade between Chile and Japan, for example.
Carbon Intensity as a Standard Definition for Hydrogen
A report by the IEA states that “Clear regulations and certification systems based on the emissions intensity of hydrogen production can bring much-needed transparency and be a useful enabler of investments in production and demand applications as well as infrastructure for hydrogen trade.”
It's apparent that carbon intensity, rather than color schemes like blue hydrogen vs. green hydrogen, can provide a unified method for evaluating environmental impact. This clarity is especially important in regions with limited potential for locally producing low-carbon hydrogen. Economies in these areas will rely heavily on imports and must be aware of the carbon impact of the products they purchase and transport.
The Role of Policy
Regulation and certification are a critical aspect of hydrogen's path forward. Policymakers should ensure that hydrogen is represented in a consistent way, ideally across the globe. Carbon intensity could be a basis for internationally recognized hydrogen regulations.
Currently, Europe, the U.S., Canada, Korea and Japan evaluate the environmental impact of hydrogen using slightly different schemes and system boundaries. Definitions from the IEA for system boundaries include:
- Well-to-Gate: Emissions produced by the supply of the fuels used in the hydrogen production process.
- Well-to-Point-of-Delivery or Well-to-Tank: Includes all well-to-gate emissions and emissions associated with transport, as well as possible conversion and reconversion of hydrogen into other carriers.
- Well-to-Wheel: Includes all well-to-gate and well-to-point-of-delivery emissions in addition to those associated with the use of hydrogen.
A unified CI scope and definition could encourage consistency and transparency across borders, smoothing the way to a scaled-up international hydrogen market.
A Clear Path to Accelerating the Hydrogen Economy
While the simplicity of the hydrogen color spectrum is useful at a high level, it does not provide a comprehensive measure of environmental impact. Embracing carbon intensity as a quantitative metric for evaluating hydrogen can aid decision-making, ultimately helping achieve emissions reduction and sustainability goals.
Hydrogen will undoubtedly play a role in the future global energy landscape. As the hydrogen economy continues to mature, let's embrace the full spectrum of possibilities it offers — not just in color but in carbon intensity as well.
Contact John Crane to learn how we can support your hydrogen initiatives.