The ecological transition is the most ambitious challenge in human history and also a response to a growing threat. As such, mistakes are common, but we have never seen one like this before: We have created black hydrogen, which is accelerating climate change when we least need it.
Hydrogen has colors: sustainability is behind this curious classification
Hydrogen is categorized by colors representing the carbon emissions associated with its production. ‘Black’ hydrogen refers to hydrogen produced through fossil fuel reforming methods that yield high carbon emissions.
Black hydrogen is made by applying stream reforming to methane or coal gasification. These processes generate carbon emissions because they rely on fossil fuels as feedstock.
The resulting hydrogen produced is considered ‘black’ due to its high carbon intensity during production. While hydrogen itself does not contain carbon, deriving it from hydrocarbons like natural gas or coal leads to substantial carbon dioxide releases.
Black hydrogen has a carbon footprint over 20kg CO2 per kg of hydrogen produced. This makes it only marginally better than using fossil fuels directly, and is compared to pink or red ones (remember that both are produced using nuclear energy).
The worst mistake in our history: the hydrogen color we should never have invented
Black hydrogen is produced from fossil fuels like coal and natural gas through a process called steam reforming. This process uses high temperatures to split the hydrocarbons in natural gas or coal into hydrogen and carbon oxides.
The most common method is to react methane (the main component of natural gas) with steam under 3-25 bar pressure at 700-1100°C over a nickel-based catalyst. The steam breaks down the methane into hydrogen and carbon monoxide. Additional water can react with the carbon monoxide to produce more hydrogen and carbon dioxide.
Coal can also be used in a similar process called coal gasification. This involves reacting the coal at high temperatures with steam and oxygen to produce hydrogen along with carbon monoxide and carbon dioxide.
Because these processes rely on fossil fuels, they generate significant carbon emissions. The carbon dioxide can potentially be captured to reduce emissions, but this is energy and cost intensive. Even with carbon capture, these methods still produce carbon emissions, which is why it is called “black” or “grey” hydrogen.
The black hydrogen problem: how it is accelerating global warming
Black hydrogen is produced from fossil fuels through processes like steam reforming of natural gas or gasification of coal. This results in significant carbon emissions compared to greener methods of hydrogen production.
Some key issues with black hydrogen production:
- Producing 1 kg of hydrogen via steam methane reforming generates between 9-12 kg of CO2 emissions. That’s substantial compared to electrolysis of water which produces minimal emissions.
- As the world moves to decarbonize, black hydrogen will be increasingly at odds with climate goals and carbon pricing mechanisms. Its high emissions have given it the label of being ‘brown’ or ‘dirty’ hydrogen.
- Black hydrogen perpetuates dependence on fossil fuels. Ramping it up provides incentives for continued fossil fuel extraction rather than transitioning to renewable energy.
- Carbon capture and storage is sometimes proposed to curb emissions from black hydrogen production. However, CCS technology has struggled to reach cost-effectiveness and fully eliminate emissions.
So while black hydrogen may appear as an easy option to tap into abundant fossil fuel resources, its climate impact makes it highly problematic. The world will need to work to transition to cleaner forms of hydrogen.
Progress and innovation are not always 100% sustainable (remember the Industrial Revolution). The question is whether we will find a way to replace black hydrogen or whether we will end up using it as a last resort. This is something we already do with other colors, such as gray or brown, which we have also told you about.