Clemons-Magee Endowed Professor in Chemistry Chris Barile, whose research centers on solving energy problems, share how we can use the most abundant element in the Universe.

Is hydrogen a promising clean energy solution?

Unlike fossil fuels, hydrogen cannot be mined or harvested, and it takes energy to produce hydrogen. Depending on how it is produced, hydrogen generation can be clean or can result in significant greenhouse gas emissions.

Importantly, hydrogen is not an energy source, but rather an energy carrier. In this way, hydrogen is similar to batteries in that it can be used to store energy. Electricity can be used in an electrolyzer to generate hydrogen from water, which is analogous to charging a battery. The hydrogen can then be utilized in a hydrogen fuel cell to generate electricity and water, which is analogous to discharging a battery.

What kinds of hydrogen are there?

Because the energy required to generate hydrogen can come from many different sources, scientists use a rainbow of colors to conveniently categorize hydrogen based on its production source. Black and brown hydrogen come both the gasification of coal, a process that releases a large quantity of carbon dioxide, thus making these hydrogen colors the least desirable from an environmental standpoint. Grey hydrogen is produced via the steam reforming of methane. In this process, steam is reacted with methane at high temperature to produce hydrogen, but also with carbon dioxide as a byproduct. Black, brown, and grey hydrogen are critical components of the fossil fuel industry, and the hydrogen generated is used in oil refining, ammonia and steel production, and as a chemical feedstock. Blue hydrogen is a cleaner alternative to grey hydrogen in which the carbon dioxide byproduct is sequestered underground using carbon capture and storage (CCS). However, because there are inefficiencies associated with CCS, it still results in some carbon dioxide release.

Over the last few decades, substantial advancements in electrolyzer technology and decreasing renewable energy costs have opened up the viability of green hydrogen. Electrolyzers can now efficiently use electricity to split water into hydrogen and oxygen gas. If the electricity used to power the electrolyzer comes from clean and renewably-sourced electricity such as solar and wind, this clean method of producing hydrogen is deemed green.

Although the color system facilitates scientific communication about the environmental impact of hydrogen from various sources, it is a bit of an oversimplification. For example, even green hydrogen is not completely “green” as this label does not take into account environmental costs associated with manufacturing and transporting the components needed for hydrogen production.

How far along are we in terms of developing green hydrogen?

Green hydrogen represents less than 1% of hydrogen produced worldwide. In the United States, the vast majority (95%) of hydrogen produced is grey hydrogen, which is generated from the steam reforming of methane.

The good news is that we already possess all the fundamental technological pieces to transition to green hydrogen. Solar and wind provide the electricity needed to produce the hydrogen, and electrolyzers are a mature technology. The technologies that use the hydrogen such as fuel cells and industrial burners are also well developed. In other words, the underpinning science and technology is ready. Widespread adoption of green hydrogen is now a question of cost competitiveness, infrastructure scaling and coordinated political will.

How might green hydrogen be used?

In the 2000s, many researchers believed that green hydrogen would serve as the primary energy carrier in the nascent renewable energy economy. We thought hydrogen would be used to power cars and homes and help us stabilize the electrical grid, while batteries were deemed too expensive and niche. An incredible series of scientific and technological advances in batteries has occurred since then. As a result, the hydrogen versus battery landscape has completely flipped, and batteries now dominate the electrification portion of the renewable energy transition. However, green hydrogen will still play an important role for areas of the energy economy that are difficult to electrify such as steel, cement, glass, many chemicals, shipping and long-haul trucking.

How big a difference will green hydrogen potentially make with respect to climate change?

Replacing grey hydrogen with green hydrogen would go a long way toward decarbonizing the aforementioned hard-to-electrify sectors. If implemented widely, green hydrogen could represent up to 20% of total energy demand by 2050, avoiding billions of tons of cumulative carbon emissions. Green hydrogen is only one part of the larger solution to climate change and must be coupled with a wide range of other green technologies.

When will green hydrogen hit the mainstream and what needs to happen first?

The cost of green hydrogen needs to drop from about $4 to $6 per kilogram to about $1 to$2 per kilogram to be competitive with less clean forms of hydrogen. The continued expansion of solar and wind capacity will drive down costs along with the scale up of electrolyzer and distribution infrastructure. Additionally, rising natural gas prices in certain regions may accelerate green hydrogen adoption by making it a more economically attractive option. Most forecasters anticipate that green hydrogen could reach 10%-20% of the global carbon emission mitigation portfolio by the mid-2030s if cost, policy and infrastructure considerations are met.