The Hydrogen Rainbow Explained

Hydrogen is poised to play a key role in the global shift away from fossil fuels toward a cleaner future. Its potential spans across transportation, heating, and heavy industry. Although abundant, hydrogen must be produced from various sources—each with different environmental impacts, known as the “hydrogen rainbow.” These colours help decipher production methods and their emissions. From green hydrogen, produced through renewable energy, to grey, blue, and beyond, understanding these distinctions is essential as we work toward a zero-emission future.

Green hydrogen is produced through electrolysis using renewable energy sources like wind and solar, resulting in zero emissions. It is one of the cleanest and most sustainable forms of hydrogen, emitting minimal greenhouse gases when burned for energy.  

Yellow hydrogen is produced through electrolysis, just like green hydrogen, but the electricity used comes from a mix of renewable energy sources and grid electricity, which may include non-renewable sources. As a result, the environmental impact of yellow hydrogen can vary depending on the energy mix used for its production. It represents a middle ground between green hydrogen, which relies entirely on renewable energy, and grey hydrogen, which is produced from fossil fuels. 

Pink hydrogen is produced through electrolysis using nuclear energy as the power source. This method generates hydrogen without emitting carbon dioxide, as nuclear energy is a low-carbon source of electricity. Pink hydrogen leverages the reliable and continuous energy output of nuclear power plants, making it a potentially significant contributor to the hydrogen economy, particularly in regions with established nuclear infrastructure. 

Grey hydrogen, the most common form of hydrogen produced today, is derived from fossil fuels, primarily natural gas, through steam methane reforming (SMR). This process releases carbon dioxide (CO2) as a byproduct, making grey hydrogen a significant contributor to greenhouse gas emissions. While it is readily available, it’s environmental cost is high. 

Orange hydrogen is produced from bioenergy sources, such as biomass, biofuel, biogas, or biomethane, which typically come from waste and residual materials. This process can result in low operational costs and potentially net-negative carbon emissions, especially if the waste used as feedstock would otherwise go to landfill. Orange hydrogen is part of the broader hydrogen colour spectrum, indicating different production methods and environmental impacts, and is considered a cleaner alternative to more carbon-intensive hydrogen production methods like grey or brown hydrogen.

White hydrogen, also known as natural or native hydrogen, is naturally occurring hydrogen found in underground deposits. Unlike other forms of hydrogen that require energy-intensive processes for production, white hydrogen is produced continuously within the Earth’s crust through natural geological processes. This form of hydrogen is considered potentially the cleanest and most cost-effective, with minimal environmental impact as it emits nearly no carbon and has low production costs. It’s simply collected as it flows to the surface. 

Blue hydrogen mitigates the environmental impact of grey hydrogen by using carbon capture and storage (CCS) technology to reduce CO2 emissions during production. Though it is also produced from natural gas, blue hydrogen is seen as a transitional solution toward a greener hydrogen economy.  

One of the newest additions to the hydrogen rainbow. Turquoise hydrogen is derived through a thermal process known as ‘methane pyrolysis’ which involves natural gas being passed through a molten metal, resulting in the production of hydrogen and solid carbon. Turquoise hydrogen is considered low carbon, if it’s powered by renewables and if the carbon is permanently stored or used for something else. 

Produced from burning fossil fuels, mainly lignite (brown) and coal (black). This process has the most potential to leave a lasting impact on our environment as a result of the high harmful carbon dioxide emissions produced in the gasification process. 

The future is clearly green and we’re starting to see the green shoots of the Green Hydrogen Sector taking hold, however to make it a mainstream energy source a few hurdles must be overcome, including; infrastructure, cost effective solutions in the production etc.

At James Cropper we are committed to facilitating the advancement of electrochemical, low carbon technologies, such as PEM water electrolysis, that can be used to generate green hydrogen from renewable energy sources