About the Hydrogen Rainbow: How Hydrogen is Made Determines Its Impact

Hydrogen is used in a variety of industries. According to the U.S. Energy Information Administration, nearly all of the hydrogen consumed in the United States is used by industry in oil refining, treating metals, making fertilizer and processing foods. It has the potential to decarbonize hard-to-electrify industries like steel-making and the manufacture of industrial chemicals like ammonia and methanol. It may also be useful for decarbonizing heavy industry, shipping, aviation and heavy-duty transport, according to the IEA.

But where does hydrogen come from? Let's take a closer look at how most hydrogen is currently produced and the challenges with these methods. 

How is most hydrogen currently produced? 

Nearly all hydrogen produced today is not green, which is to say, it’s not environmentally sustainable. At the end of 2021, almost 47 percent of global hydrogen production was made from methane, 27 percent from coal and 22 percent from oil (as a by-product), according to the International Renewable Energy Agency. Only around 4 percent came from splitting water apart with electricity, called electrolysis.

As a result, making hydrogen is responsible for around 830 million tons of carbon dioxide emissions per year, equivalent to the CO2 emissions of the U.K. and Indonesia combined. Since only about a third of electricity globally is produced from renewables, that means only about 1 percent of global hydrogen is green — as in, made with renewable energy. 

This matters because if we want to meet the Paris agreement target of limiting global warming to 1.5 degrees Celsius, we need to stop using fossil fuels. Ending fossil fuel dependence also includes stopping the use of fossil fuels to make hydrogen — and investing more in technologies that are powered by renewables. 

What is gray hydrogen? 

Gray hydrogen is made from methane (CH4), a fossil fuel. The International Energy Agency has noted that 6 percent of global methane (natural gas) production goes to making hydrogen. When you burn methane with oxygen in the air, you produce carbon dioxide, a greenhouse gas, and water. 

What is black or brown hydrogen?

This kind comes from coal, accounting for 2 percent of global coal production, according to the International Energy Agency. You can turn coal into a gas in a process called gasification. Since coal has a lot of impurities in it compared to methane, including sulfur and nitrogen, burning coal yields nasty stuff like carbon monoxide (CO), hydrogen sulfide, as well as ammonia. Hydrogen sulfide and ammonia are very reactive, and when they are emitted into the atmosphere, they contribute to acid rain. You can read more about the chemistry of gasification here. 

What is blue hydrogen? 

Blue hydrogen made from methane, just like gray hydrogen, but the resulting carbon dioxide emissions are supposedly captured. However, captured carbon is most commonly used for enhanced oil recovery — accounting for about 75 percent of all captured carbon use in the U.S. and about 88 percent globally. 

The problem is: If you capture carbon dioxide and use it to produce more fossil fuels, you’re actually enabling more carbon dioxide emissions, furthering global warming. Even if you purified the CO2 and put it in soft drinks, for example, the carbon dioxide just bubbles back into the atmosphere, and all that work to capture it is kind of a waste.

For these reasons, blue hydrogen won't actually help to address global warming. Additionally, fossil fuel companies are paying lobbyists to support blue hydrogen, like in this U.K. example. We need to pull carbon dioxide out of the air and store it permanently, underground, not continue to use carbon capture and utilization as an excuse for delaying getting off fossil fuels.

What is turquoise hydrogen?

If you burn methane in a low-oxygen environment through a process called pyrolysis, you can make just carbon rather than carbon dioxide as a result, along with the desired hydrogen. While this might seem better than the other approaches because carbon is easier to store than carbon dioxide, you still have to use methane as a starting point.

Starting with methane means you need to separate the methane from the source where it’s drilled from: natural gas, other hydrocarbons, water, carbon dioxide, nitrogen, oxygen and some sulfur compounds. (If you remember from earlier, sulfur and nitrogen compounds in fossil fuels contribute to acid rain.) And, who benefits from methane extraction? The fossil fuel industry, because fracking or drilling for hydrocarbons including methane lets them keep doing what they’ve been doing for decades. 

What is pink or red hydrogen?

Pink or red hydrogen is created from breaking apart water through electrolysis using electricity supplied by nuclear energy sources. While nuclear energy has some proponents for it being helpful for reducing our greenhouse gas production, it fails the test of climate justice. If you watch this training from the Midwest Building Decarbonization Coalition, a climate justice network, nuclear is still a climate justice concern.

Today, nuclear waste is largely stored onsite where it’s generated. Where do we think we’ll put that waste when the storage room runs out? If current pollution trends continue, it’s likely  to be near where Indigenous people or people of color live. That’s not right. Using nuclear energy is attempting to fix this generation’s carbon problem by punting the pollution to future generations. 

Meanwhile, a Stanford University study found there is plenty of wind to provide half the world’s power by 2030, and BloombergNEF thinks wind can power half the world by 2050. Why are we running on nuclear power when we can run on renewables? For those who argue “well, we need more base load power and the sun doesn’t shine and wind doesn’t blow all the time,” consider pumped hydro or building more wind turbines near electrolyzers, and the hydrogen itself can store the energy. 

In this second part of this two-part article, we examined things to look for related to disinformation and greenwashing and dive deeper into the differences between hydrogen that is green — and isn't. Click here to read it. 

Land Acknowledgment: Katharine is a Mayflower descendant who lives and works in unceded Lisjan Ohlone territory, what is now known as Oakland, Berkeley, Alameda, Piedmont, Emeryville and Albany, California. The Sogorea Te’ Land Trust is an urban Indigenous women-led land trust that is today working hard to restore traditional stewardship practices on these lands, heal from historical trauma, and facilitate the return of Indigenous land to Indigenous people. May they be successful in their work!