The United States has long been a major contributor to global greenhouse gas emissions. However, in the summer of 2023, the Biden-Harris Administration took a significant step toward building a cleaner energy future by embracing the potentials of hydrogen power.

Hydrogen, an abundant environmental resource, has been hailed for decades as a promising clean energy carrier across many sectors. And the most common process for producing it, electrolysis, has been around for centuries. Unlike fossil fuels, which generate substantial carbon dioxide (CO2) emissions, generating power from hydrogen produces only water vapor. Nevertheless, the main hurdle in utilizing hydrogen as a clean energy carrier is its scarcity in pure hydrogen gas, H2.

While hydrogen is plentiful in the universe, on Earth it rarely exists in its pure state. Instead, it typically exists in compound forms such as H20 or in organic matters like coal and natural gas. Extracting or separating hydrogen from these compounds requires an energy input. The environmental footprint of the resulting hydrogen depends largely on the source of this required energy input. In fact, the Department of Energy still highlights thermal processes and electrolysis as the predominant methods of hydrogen production. To better understand and differentiate the climate impact of differing methods, scientists have developed a classification system aptly termed as “the colors of hydrogen.”

The Colors of Hydrogen

‘The colors of hydrogen’ categorizes H2 into various colors based on its production method, the energy source used to power the separation process, and connected levels of greenhouse gas emissions. Currently, hydrogen sources are classified as black, gray, brown, blue, or green, with black being the most environmentally harmful and green having neutral carbon emission levels.

Black or Brown Hydrogen

Hydrogen classified as black or brown is considered environmentally detrimental because of its significant CO2 emissions when compared to other production methods. In fact, blak or brown methods emits roughly twice as much carbon as gray hydrogen production. Because of its environmental impact, production of H2 from this method has been declining in recent years.

Both black and brown hydrogen use the production method of coal gasification. Gasification is the conversion of coal into synthetic gases which includes carbon monoxide (CO), nitrogen, hydrogen, and carbon dioxide (CO2).  Although hydrogen is separated for use, CO2 and CO are usually released into the atmosphere as neither have significant reuse applications.

Black hydrogen, processed from bituminous coal, contains a high carbon content, ranging from 50-80%. On the other hand, brown hydrogen comes from lignite coal, the lowest-grade coal, containing only 20-30% carbon, resulting in less environmental damage compared to bituminous coal.

The origins of coal gasification trace back to the late 1790s when it was developed to produce “town gas” for lighting, heating, and cooking in urban settings. The production of black and brown hydrogen became prevalent owing to their economic advantages and the ready availability of coal resources. However, with the rise in the accessibility and abundance of natural gas during the 20th century, gasification of coal has fortunately seen a declining share of hydrogen production.

Grey Hydrogen

As of 2020 in the U.S., gray hydrogen makes up 95% of hydrogen production, and stands as the predominant method of production worldwide. Even though gray hydrogen production emits less than black or brown methods, grey still releases a substantial amount: between 9-13 kg of CO2 for every kg of hydrogen produced.

Grey hydrogen is primarily produced through steam-methane reforming.  In this process, natural gas containing methane encounters high-temperature steam in the presence of a catalyst. This interaction breaks the gas down into hydrogen, CO and CO2. Much like with black and brown hydrogen, a significant portion of the CO and CO2 byproduct ends up in the atmosphere, exacerbating climate change.

Blue Hydrogen

Blue hydrogen is a process strikingly similar to gray hydrogen, with the exception of releasing CO and CO2 back into the atmosphere. Hydrogen is considered blue when most of the resultant carbon emissions are captured and either stored or utilized.

Blue hydrogen is labeled as ‘low carbon.’ It’s most effective when capturing well over 90% of the emitted carbon. Yet, the actual capture rates often fall short. For instance, a Shell facility in Canada reported a capture rate of only 43% in January 2022. To put that into perspective, a 56% capture rate corresponds to around 5 to 9 kgs of CO2 emissions, while 90% drops it to 1 to 4.5 kg.

Furthermore, methane leaks pose another challenge. Even before the carbon capture process starts, leaks can occur. During the production, processing, and distribution of natural gas, methane emissions are, sadly, almost inevitable. This potent greenhouse gas can also escape from infrastructure, pipes, and equipment. Though methane’s atmospheric lifespan is shorter than CO2’s, its greenhouse effect is significantly stronger.

Captured CO2 has multiple applications; industries repurpose it for commercial uses like dry ice production, beverage carbonation, and industrial process cleaning. However, these applications merely delay the CO2’s eventual release into the atmosphere. A more sustainable solution, being explored by researchers globally, is to either store the carbon underground or incorporate it into building materials such as asphalt for roadbeds and roofing shingles.

Green Hydrogen

Green is the global goal. As of 2020, only 1% of hydrogen production falls under the category of green hydrogen, also known as ‘clean hydrogen.’ Comparatively dirty hydrogen, derived from fossil fuels, or using processes powered by fossil fuels, still constitutes 99% of U.S. hydrogen production today.

Green hydrogen sets itself apart by eliminating all carbon emissions. It leans heavily on renewable energy sources instead of fossil fuels to power hydrogen extraction. The primary production method is electrolysis of water, whereby electricity from renewable sources, such as solar, wind, or geothermal power, is used to split water into oxygen and hydrogen components. Though this method is the most environmentally friendly, it also carries the highest production costs.

With the Biden-Harris administration’s support for cleaner and lower-cost hydrogen, significant investments have been made by various companies to develop novel and environmentally friendly hydrogen production methods. One such initiative is Oceanit’s HALO project, which is deriving hydrogen from wastewater, marking another promising stride in the pursuit of sustainable hydrogen production. The end-goal is to power HALO with renewable energy sources and recover hydrogen and other value-add minerals from unusable waste waters.

The global transition from fossil fuels to hydrogen is regarded as a crucial step towards achieving a sustainable and eco-friendly energy landscape.

To learn more about hydrogen, visit ‘Friday 5 things to know about a hydrogen fuel future’.