Hydrogen is often heralded as a climate hero because when it is used as a fuel in things like buses or steel production, there are no direct carbon emissions (or associated warming) to worry about. . As the world tries to cut back on our use of fossil fuels, there may be a lot of new demand for this carbon-free energy source.
But how hydrogen is made may determine how helpful it is for the climate. That’s where the rainbow comes in. (I’ve added an at-a-glance table below so you can remove all of these colors.)
Last week, the European Commission released the rules that define what is “renewable” hydrogen: in other words, what hydrogen means GREEN. There was also an interesting story in Science last week about naturally occurring, o GOLDhydrogen.
So let’s dive into the hydrogen rainbow and explore where this fuel will come from in the future.
What do we need for hydrogen?
We use a lot of hydrogen today: the global demand is 94 million metric tons (Mt) in 2021. Most of that is used for oil refining, as well as the production of ammonia (for fertilizer) and methanol (for chemicals manufacturing).
That is likely to change in the future, as it is also a good substitute for fossil fuels in transportation, heavy industry, and other sectors. If countries keep their climate commitments, hydrogen demand could reach 130 Mt by 2030, and about a quarter of that for new uses.
The problem is, making hydrogen today requires a lot of fossil fuels, mostly natural gas. In so-called “gray” hydrogen production, natural gas reacts with water, producing hydrogen gas and giving off carbon emissions.
It doesn’t have to be that way, though. For one thing, we can try to get carbon emissions from fossil-powered hydrogen production (this method can provide the so-called blue hydrogen). This is a somewhat controversial method, as carbon capture is expensive and does not always work efficiently.