The Hydrogen Rainbow

By: Jacob Barrons

Hydrogen is the most abundant element in the universe. It is a colorless, odorless gas that has been brought center stage in the debate around renewable energy.

Hydrogen has a plethora of uses in numerous industries from, glass-making to plastics and pharmaceuticals, but its use as a fuel contributing to the clean energy transition is where many now see its future.

Hydrogen has been used as a fuel source since the 1950s when NASA developed it as a rocket fuel and used hydrogen fuel cells to power the electrical systems on spacecrafts. Today hydrogen can generate energy in a number of ways; as fuel cells that combine hydrogen and oxygen, burning it in a power plant to turn turbines, and as a vehicle fuel. These various methods of generating power utilizing hydrogen have led to the proliferation of hydrogen “colors”.

The colors are the classification system of hydrogen that relate to what powers the chemical process that extracts it and turns it into a fuel.

The primary colors of hydrogen are grey, blue, green, black, pink, turquoise, and yellow. The three most used colors are grey, blue, and green.

Grey hydrogen, which includes black, is hydrogen produced when using fossil fuels as the power source in a steam-powered process that then allows the hydrogen to be used as a fuel source in multiple applications. The CO2 created by the breaking down of fossil fuels is released directly into the atmosphere and contributes to 2.2% of global annual emissions. Grey hydrogen is not a renewable energy source.

Blue and turquoise hydrogen both utilize fossil fuels in a similar process to grey hydrogen in order to produce hydrogen that can be used as a fuel source. Both blue and turquoise hydrogen are offered up as clean energy by the fossil fuel industry because they have carbon-storing elements in their processes. Blue hydrogen creates a by-product of carbon dioxide that is then captured using carbon capture, utilization, and storage technologies (CCUS). Turquoise hydrogen creates a solid carbon by-product.

Both blue and turquoise hydrogen are advertised as climate-neutral alternatives to grey and black hydrogen but CCUS processes do not necessarily lead to emissions reductions. There are numerous variables including, how to store captured carbon and the scalability of those technologies, and how long carbon can be stored that limit the emission reductions possible.

Pink hydrogen utilizes nuclear energy in powering the process of converting water into oxygen and hydrogen. It has a significantly smaller carbon footprint than any of the other aforementioned colors but is a less efficient use of energy as nuclear energy could directly power most of what the pink hydrogen would be used to power.

Green hydrogen is the only truly carbon-neutral option for hydrogen production. It uses renewable energies in its process of converting water into oxygen and hydrogen. It maintains the inherent inefficiencies similar to pink hydrogen because those renewable energies could directly power many of the same technologies that hydrogen would, but hydrogen has applications in industry that renewable energy electricity does not.

Understanding the differences in the colors that characterize the production of hydrogen is essential to making a clean energy transition. While the fossil fuel industry continues to lobby for the application of blue and turquoise hydrogen, an educated voter base that understands that these words are greenwashing the problems with CCUS technologies will be able to hold their local governments accountable.

Green hydrogen is a tantalizing technology for the future that must be given an opportunity even as it contends with its nonrenewable siblings. Just as an educated voter base can sniff out the greenwashing that is done using black and blue hydrogen, they can also understand the important role that green hydrogen can play in a renewable economy.