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(image from “The economics and the environmental benignity of different colors of hydrogen” by A. Ajanovic, M. Sayer, and R. Haas)

Hydrogen is the most abundant element in the known universe. Like electricity, hydrogen in its gaseous H2 form holds the power to transport, store, and convert energy. To date, hydrogen is mostly used as a chemical substance; predominantly in various industrial processes, such as refining, steel production, ammonia production, and methanol production. Nevertheless, there are other applications for hydrogen. According to the International Energy Agency (IEA), the main uses are to store excess energy from renewables as H2 either to convert it back into electricity (very inefficient) or to use it in industrial processes, to inject it into natural gas grids or to use it in the transport sector in fuel cell vehicles.

Since hydrogen exists in a gaseous state at average temperatures, storage and transportation are challenging compared to denser fuels like coal, but H2 can alternatively be stored as ammonia, which is a liquid at average temperatures. Ammonia is a promising carrier due to its efficiency, versatility, and economic viability.

Sustainable hydrogen production hinges on renewable electricity, not the current grid. This distinction is paramount, as relying solely on green electricity presents challenges. Lower operating hours due to the natural variability of sun and wind (except for hydropower) increase electrolyzer costs. Additionally, renewable electricity costs must decrease to offset this investment difference.

The comprehensive hydrogen review article published by A. Ajanovic, M. Sayer, and R. Haas dissects various production methods, comparing their technical, economic, and environmental aspects. It underscores the critical role of choosing the right method for maximizing environmental benefits. Only “green hydrogen” produced from wind, solar, and hydro electricity boasts truly low emissions. Other sources, including “blue hydrogen” with carbon capture and storage, still emit significantly, approaching levels of “grey hydrogen” derived from fossil fuels.

Furthermore, establishing an international hydrogen market can lower costs and optimize production based on regional advantages. While a universal definition for “green hydrogen” remains elusive, initiatives like the EU’s “CertifHy” project are developing certification schemes.

A key question persists: even considering all external costs, can any color of hydrogen become economically competitive across the energy system? The future success of hydrogen hinges on technological advancements, cost reductions, policy frameworks, and shifting priorities towards sustainability.

Currently, grey hydrogen reigns supreme in terms of cost, ranging from 0.8 to 2.1 € per kg. Blue hydrogen incurs higher costs due to carbon capture, while green hydrogen exhibits a wider range (2.2 to 8.2 € per kg) due to varying assumptions about operating hours and energy costs. However, green hydrogen is expected to significantly decrease in cost thanks to technological advancements and increased efficiency, potentially outcompeting blue hydrogen by 2030.

Demand for hydrogen has steadily grown in industrial applications like refining, steel, ammonia, and methanol production. Steam reforming of natural gas remains the most developed and cheapest method, contributing the majority of hydrogen production but releasing around 900 Mt of CO2 annually.

While some studies in the report highlight the current economic advantage of grey hydrogen, others point towards high-temperature electrolysis with biogas as the most efficient method, and others emphasize the incompatibility of fossil fuel-based hydrogen with a sustainable future. Notably, fugitive methane emissions often go unaccounted for in most blue hydrogen assessments.

An array of Colors:

Grey Hydrogen

  • Grey hydrogen is currently the most widely produced type of hydrogen, generated from steam reforming of natural gas or coal gasification without carbon capture, utilization, and storage (CCUS).
  • It is mainly used in the petrochemicals industry and for ammonia production.
  • The major disadvantage of grey hydrogen is the significant CO2 emissions generated during its production, estimated to be around 830 Mt CO2 per year.
  • Despite the high emissions, steam reforming of natural gas without CCUS is a well-established process, resulting in low hydrogen costs.

Green Hydrogen

  • Green hydrogen is produced using electricity from wind, photovoltaic (PV), and hydroelectric sources.
  • It has truly low emissions compared to other sources, making it an environmentally friendly option.
  • With technological advancements, costs for green hydrogen are expected to substantially decrease, making it a promising option for the future.
  • Newborough and Cooley state that Green hydrogen will be the production method of the future as it will become cheaper than the alternatives like blue hydrogen caused by cheaper renewable electricity and electrolyzers.
  • In addition, the question of the classification of green hydrogen is still unresolved. There is no universal definition to date, but the EU project CertifHy is developing hydrogen certification schemes in Europe

Blue Hydrogen

  • Blue hydrogen is produced from natural gas with carbon capture, utilization, and storage (CCUS) or from methane through autothermal reforming (ATR) with CCUS.
  • It has substantially higher emissions compared to green hydrogen but is considered more environmentally friendly than grey hydrogen.
  • The review points out that blue hydrogen production with CCUS or electrolysis using the electricity grid has emissions that are close to grey hydrogen production.

Turquoise and Pink Hydrogen

  • Turquoise and pink hydrogen are also discussed in the review, with turquoise hydrogen being produced from methane pyrolysis with CCUS and pink hydrogen being produced from methane cracking with CCUS.
  • These methods are relatively less common compared to grey, green, and blue hydrogen, and their economic and environmental implications are also analyzed in the review

Emerging Colors under early development:

  • Aqua: by the University of Calgary from oil sands/fields with supposedly zero emissions
  • White: direct water splitting with solar to be tested in Saudi Arabia
  • Purple: Hydrogen production by nuclear electricity
  • Biomass feedstocks: converted into hydrogen by thermochemical processes, gasification, fermentation, or microbial electrolysis

Choosing the right “color” of hydrogen is crucial. While grey might be the immediate choice, its long-term impact is unsustainable. Green, with its proposal of clean energy and falling costs, seems poised to lead the charge. However, blue, purple, and others may play crucial roles depending on specific contexts.

Utilizing the full potential of hydrogen requires careful selection of production methods based on cost, emissions, technological maturity, application, and regionally available resources.

            Our next article will focus on the feasibility of implementing H2 in cement production.