Hydrogen beyond renewables: Tapping energy beneath our feet

According to the International Energy Agency’s Global Energy Review 2025, global CO₂ emissions from energy and industrial processes rose from about 4 gigatonnes in 1990 to nearly 38 gigatonnes in 2024. The contrast between regions is striking: Europe has successfully reduced its emissions (from 3.5 Gt in 2000 to 2.5 Gt in 2024), while China’s emissions have surged (from 3.5 Gt to 12.5 Gt). These numbers highlight the urgent need to rethink how we produce and use energy.

One promising alternative is hydrogen.

Why hydrogen matters

Hydrogen is the most abundant element in the universe and an energy carrier with huge potential. Scientists and engineers often call it a game-changer because it produces no CO₂ emissions – when hydrogen reacts with oxygen, it produces only water and heat. It has a high energy density, storing more than three times the energy of gasoline by weight. Hydrogen can also store excess renewable electricity for later use, bridging gaps when the sun doesn’t shine or the wind doesn’t blow. In addition, it has a significant industrial impact, being especially useful for hard-to-decarbonise sectors like steelmaking, chemicals, and heavy transport.

Hydrogen in Finland: A big opportunity

According to the Clean hydrogen economy strategy for Finland, Finland aims to become the leading high-value hydrogen economy in Europe by 2035. Already, 89% of Finland’s electricity is carbon-neutral, making it ideal for producing green hydrogen via electrolysis. The country also has huge potential for wind energy, with projects in development that could add 120 GW. In addition, Finland has abundant natural resources – metals, biogenic CO₂, and water – needed for hydrogen derivatives like synthetic fuels and clean steel, as well as a skilled workforce and a strong R&D ecosystem. By 2035, Finland could produce 3 million tonnes of clean hydrogen annually, creating €16–34 billion in economic value and up to 60,000 new jobs.

The many “colours” of hydrogen

Not all hydrogen is produced the same way. Scientists often describe hydrogen by “colours,” depending on the production method. For example, grey hydrogen is made from natural gas; it is cheap but emits CO₂. Blue hydrogen is similar but paired with carbon capture and storage (CCS). Green hydrogen is produced from renewable electricity and water; it is the cleanest but currently the most expensive. Another emerging pathway is turquoise hydrogen, produced by methane pyrolysis. Without catalysts, this requires temperatures of around 1000 °C, but with advanced catalytic processes the reaction can occur at only a few hundred degrees. Today, around 96% of hydrogen production is fossil-based, but green hydrogen is rapidly gaining momentum worldwide.

Natural hydrogen: Energy from the Earth itself

The Earth also produces hydrogen naturally through geological processes, such as when water reacts with iron-rich rocks. This naturally occurring “white hydrogen” can be formed underground through processes like serpentinisation, where magnesium-silicate rocks rich in iron react with water at 200–400 °C, releasing hydrogen.

Building on this, researchers are exploring orange hydrogen, a proactive approach where water is injected into reactive rock formations to stimulate hydrogen generation. The hydrogen-rich water can then be collected from recovery wells. Orange hydrogen can be pursued in two main ways. In-situ production involves injecting water directly into natural underground formations, where hydrogen is generated and then collected through recovery wells. This has the advantage of scale but poses challenges such as controlling reactions, maintaining porosity, and managing fluids deep underground. Ex-situ production, in contrast, involves extracting reactive rocks and processing them in controlled laboratory reactors. This allows precise control over temperature, pressure, mineralogy, and water composition, making it possible to study reaction kinetics, optimise yields, and minimise by-products.

In this PhD research project, we focus on the ex-situ approach, recreating natural hydrogen-generating processes in the laboratory. The work involves designing and testing a specialized experimental setup that allows the team to study these reactions under controlled conditions, while also examining how the minerals’ structure and composition change during the process. This approach helps build a clearer picture of both hydrogen generation and the transformations occurring in the rocks themselves.

This research is carried out in the Fibre and Particle Research Unit, under the supervision of Associate Professor Tero Luukkonen and co-supervision of Associate Professor Juho Yliniemi. The project is funded by H2FUTURE research programme for one year, and we are seeking additional support from other foundations to continue this work.

Looking ahead

Hydrogen – whether green, white, or orange – has the potential to reshape the global energy system. It offers a pathway to reduce emissions, store renewable power, and fuel industries that are otherwise difficult to decarbonise. Orange hydrogen is particularly exciting because it draws inspiration from natural geological processes while allowing controlled optimisation in the laboratory.

At the University of Oulu, our ex-situ orange hydrogen project is an important step toward Finland’s goal of becoming a hydrogen leader by 2035 and contributing to the global transition to clean, sustainable energy. By understanding the reactions between water and reactive minerals, we aim to maximise hydrogen yields and improve process efficiency.

Science may be complex, but our vision is simple: A world where clean hydrogen flows not just from renewable electricity, but also from the rocks beneath our feet.